New ZR-1. New Issue. Stalling Once Warm.

[Erik]

Don?t it always work that way. A few days into my ownership (or does she own me?) 996 started acting up.

For the first few days, I just took it easy. Was gonna get it in to the local Corvette guy for an inspection anyway. Started off with some short rides. As I got more comfortable, started expanding the range a bit. Finally was getting pretty comfortable so did some shopping, kicked a round a bit, and went and gave her a fresh tank of premium. Shortly after filling up, she coughed once. Not a backfire, but what felt like a fuel system cough. Meh, old gas working it?s way through, I thought. Got home ok. Parked for a while, and thought I?d taken her for a short run before dinner. As I?m toddling around, she coughs again. Then a few more times. Then a stall, starts up ok. Then does it a couple of more times. This is all slow speed, low gear, in the neighborhood stuff. Finally manage to nurse her home, and sent her off to the mechanic by flatbed to get the planned check over done.
Now, before the fresh tank of gas, she had run fine. Hadn?t pushed her to the redline yet, but 6000 rpm pulls felt good. Felt very smooth under power. Idle was ok. Seemed to want a couple of seconds cranking, but I?m used to modern cars that start so quickly, that the slightly longer cranking time might just be me.

Took her to the mechanic, and the good news is that all the mechanical stuff is good. Brakes, suspension. No oil leaks. Good structure. Nice, well kept car.

The bad news? It?s still doing the weird idle and coughing thing.

Here?s what it does:
-cold start. Starts up ok. Idles smoothly. No issues
-runs great until warm, then it starts running rough and wants to stall.
-give it gas. Keep it over 1000 rpm and it feels ok.

I had bought some parts for winter time projects, but it seemed a good idea to use them now. So, we replaced:

-Both fuel pumps, with New Delco ones. Socks, tee, etc
-Fuel filter
-spark plugs - just because. Idle smoothed out with new plugs in.

I spoke to Marc Haibeck on the weekend, and his first thought was fuel too.

Mechanic is gonna drain the tank today and see what it looks like in there. Not a lot of use over the past decade, so it could have a fair pit of crap inside.

Btw, the injectors were replaced by the previous owner.

Yes, when It was acting up, it sure felt like fuel. Maybe a bad carburetor? :)

Appreciate any thoughts.

[Erik]

And as luck would have it, my mechanics old, rarely used tech 1 decided to pack it in.

[Jagdpanzer]

Sounds like the primary fuel pump has failed. Same thing happened to my 94 which had seen a lot of storage before I acquired it.


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[Erik]

Sounds like the primary fuel pump has failed. Same thing happened to my 94 which had seen a lot of storage before I acquired it.


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Thanks, Phil.

Which I figured would happen too. But we swapped it out with a new one, and it's still doing the same thing.

He will delve into the tank today, and see what the bottom of it looks like!

[BigJohn]

Y?all have changed fuel filters?
Some times crud from bottom of fuel tank.

[Erik]

Y?all have changed fuel filters?
Some times crud from bottom of fuel tank.

Yup. The fuel filter got changed the same time as the pumps did. They will be cleaning out the bottom of the tank today.

Thanks, BigJohn

[-=Jeff=-]

While I don't have a Tech 1. I am using ALDLDroid and TunerPro to log data from my 1990. it is great to see many things at once. that might help for troubleshooting the problem. especially if it is happening as soon as it goes into closed loop. A fresh set of o2 sensors might help as well

[Erik]

While I don't have a Tech 1. I am using ALDLDroid and TunerPro to log data from my 1990. it is great to see many things at once. that might help for troubleshooting the problem. especially if it is happening as soon as it goes into closed loop. A fresh set of o2 sensors might help as well

Hi Jeff.
What do you use to connect your phone or computer to your car? A USB to OBD1 connector of some kind?

[-=Jeff=-]

OH yeah that info will help. LOL

I have a USB to ALDL cable that I typically use.. forget where I got it

I also have a Bluetooth adapter:
http://www.1320electronics.com/12pin_ALDL_BT_MK2.html

other use this one Bluetooth adapter
http://www.reddevilriver.com/ALDL_Bluetooth.html

they also sell the USB to ALDL
http://www.reddevilriver.com/aldl.html

for ALDLDroid, it is only avail for android. I use a Nexus7 Tablet..

[Erik]

OH yeah that info will help. LOL

I have a USB to ALDL cable that I typically use.. forget where I got it

I also have a Bluetooth adapter:
http://www.1320electronics.com/12pin_ALDL_BT_MK2.html

other use this one Bluetooth adapter
http://www.reddevilriver.com/ALDL_Bluetooth.html

they also sell the USB to ALDL
http://www.reddevilriver.com/aldl.html

for ALDLDroid, it is only avail for android. I use a Nexus7 Tablet..

Any preference between the 1320 Electronics stuff and the Red Devil River?

Looks like the Bluetooth version would be the one to get. Does it stay connected well? The price difference at Red Devil River is pretty small. I have old Android devices kicking around that I can put to use.

Or, is there a good reason for using something like a laptop?

Thanks! This is awesome info!

[Ccmano]

I have the Red Devil River Bluetooth connector. It works but can be glitchy staying connected. I hear the 1320 Electronics piece is less so.
H
:cheers:

[Erik]

1320 one ordered.

[Erik]

Fuel tank emptied. Relatively clean inside, but the gas was old. Cleaned out and fresh gas put in. Still idles rough when warm, but doesn't stall anymore. A step in the right direction.

So what else happens when she gets to operating temperature?

[rush91]

Stupid question, but have you cleaned your battery terminals? Doesn't hurt to take a wire brush to them. Your problems don't sound electrical, but you never know.

[ram_g]

Electrical resistance changes with temperature, so I agree with rush91. But everything electrical underneath the hood could be the issue, including injectors, coils, etc. I know you said the PO replaced the injectors but it may be worth checking their resistances cold and hot. Never done this myself but IIRC Marc Haibeck had written a procedure.

Edit: once it's running, the alternator would be more the culprit than the battery.

[Erik]

The one odd thing is that it ran ok until the first fill up. The issues started immediately after. But I'll keep checking everything!

The car has been well kept by a loving owner. I think most of the issues stem from why he sold it. That is, he just hadn't been able to drive it much over the past few years.

[32valvZ]

Have you put an ohm meter to the injectors yet? I know you said they were replaced, but Id still check them after warm up...

[Erik]

Have you put an ohm meter to the injectors yet? I know you said they were replaced, but Id still check them after warm up...

Nope. Sure haven't. Worked from the idea that they would be replaced, which means they are good. But you know how well that often works.

May have to look into what's involved with that. Is that a plenum off deal?

[viper107]

Is this a 90 or 91 car? , If so injectors and ecm allways fail

[Zman]

I had a car that did exactly what you describe. Injectors failing after warming up was the issue. I've been told even new replacements can fail, although I have not had that happen thus far.

[32valvZ]

Nope. Sure haven't. Worked from the idea that they would be replaced, which means they are good. But you know how well that often works.

May have to look into what's involved with that. Is that a plenum off deal?

Per Mr. Haibeck

http://www.zr1specialist.com/HAT%20Web/articles/Measuring%20Fuel%20Injector%20Resistance%20with%20 the%20Plenum%20in%20Place.pdf

[Erik]

Per Mr. Haibeck

http://www.zr1specialist.com/HAT%20Web/articles/Measuring%20Fuel%20Injector%20Resistance%20with%20 the%20Plenum%20in%20Place.pdf

Thank you!
Great read. Marc Haibeck rocks.

[Erik]

The cooling system came out today. Rad in nice shape, but not too dirty. Thermostat was jammed though. No way it would close all the way. Getting a whole new set of Haibeck hoses while it's apart. New thermostat and gasket from Marc too.

It's all stuff I had budgeted for when I bought it, but maybe not quite so soon. :)

The encouraging thing is that everything we look at shows a car that has been well cared for, is mechanically solid, but just hasn't been used much of late. So pretty well what I hoped for.

[BigJohn]

Good time to get a larger Radiator

[Erik]

:handshak:Good time to get a larger Radiator

I looked into it, but the timing won't work. Wouldn't have one up here until later in October at best.

[Erik]

Lots of good maintenance work done, but the initial problem is still there. It feels like fuel, but it still does it with two new fuel pumps.

[Erik]

So we keep getting closer. IAC is reading way open. It's reading 150. Also, temperature readings are weird. Engine off, it's showing -40F. When it's running, 315F. I'm guessing those readings might not be totally accurate. :)

[Erik]

And another month went by, with this mechanic getting no closer. Sure, we got a lot of stuff done that isn't a bad thing for a 30 year old car. However, it was getting more and more obvious, that he wasn't actually troubleshooting, but rather just swapping parts. Argh!

If not for the Covid situation, I'd have it down in the US, visiting someone like Graham or Marc, and likely be up and running in a day. Sigh.

[Mystic ZR-1]

So we keep getting closer. IAC is reading way open. It's reading 150. Also, temperature readings are weird. Engine off, it's showing -40F. When it's running, 315F. I'm guessing those readings might not be totally accurate. :)

-40F? Hope you've got green anti freeze in it...

[Paul Workman]

Nope. Sure haven't. Worked from the idea that they would be replaced, which means they are good. But you know how well that often works.

May have to look into what's involved with that. Is that a plenum off deal?

From the "School of Hard Knocks": Replace AND THEN CONFIRM!

When I bought my Z from a dealer specializing in Corvette sales, the injectors were "replaced" before hand, but replaced with NOS (new old stock). Later, I measured resistance of the injectors of a WARM engine and discovered several were a couple ohms below the average of the rest, and one that was 4Ω lower (read 8 instead of the 12 ohms that was the average value for most of the rest).

That said by others too, when you first start a cold engine, both fuel pumps run for a short time, AND the ECM is in OPEN LOOP mode which means fueling is from the tables and the O2s are not being considered. After the engine temp comes up the secondary fuel pump shuts off and the ECM switches to CLOSED LOOP: a double whammy!

One of the best tools I ever bought for the Z right away was an OBD-I scanner and the Factory Service Manual (FSM). -=Jeff=- and Dominic and many others have moved to TunerPro software and the ALDL/USB cable connected to a tablet. That sounds like the way to go in lieu of a Tech-1 or other scanner(s). With that setup you can instantly see everything going on with the sensors and the tune parameters. No more having to guess and buy a lot of parts that may or MAY NOT be as good as the original parts (considering how many are made "over seas".[-X

[Erik]

It would seem that my ZR-1 is back up and running again. The biggest problem? An idiot mechanic. I'm more pissed off then I can say. Yes, a lot of stuff got done, most of which is really good maintenance work. However, It cost me the entire fall driving season. Which pisses me off the most.

Anyhow, I finally got fed up with this guys incompetence, and towed it 2 hours to someone I understand had experience with the LT5. Anyway, 4 hours of maintenance time, and they had the problem found.

I'm pretty much a forgive and forget kind of guy, but thoughts of suing the first mechanic keep popping up in my head.

I hope to have the car back in the next couple of days. Once I've driven it and found it to be sound, I'll post more!

[WARP TEN]

It would seem that my ZR-1 is back up and running again. The biggest problem? An idiot mechanic. I'm more pissed off then I can say. Yes, a lot of stuff got done, most of which is really good maintenance work. However, It cost me the entire fall driving season. Which pisses me off the most.

Anyhow, I finally got fed up with this guys incompetence, and towed it 2 hours to someone I understand had experience with the LT5. Anyway, 4 hours of maintenance time, and they had the problem found.

I'm pretty much a forgive and forget kind of guy, but thoughts of suing the first mechanic keep popping up in my head.

I hope to have the car back in the next couple of days. Once I've driven it and found it to be sound, I'll post more!

Best approach: Move forward; forgive and forget. You will feel much better for it. Most mechanics don't know much if anything about the LT5. Lesson learned. If you have now found a mechanic who does know a little about ZR-1s, put him in touch with the ZR1Net Registry forum or better, Marc Haibeck or some other specialists. Usually they are all glad to help. Take a deep breath and enjoy your great car. --Bob

[Erik]

Best approach: Move forward; forgive and forget. You will feel much better for it. Most mechanics don't know much if anything about the LT5. Lesson learned. If you have now found a mechanic who does know a little about ZR-1s, put him in touch with the ZR1Net Registry forum or better, Marc Haibeck or some other specialists. Usually they are all glad to help. Take a deep breath and enjoy your great car. --Bob

I did a lot of that over the past few months. But there?s also just a matter of old fashioned right and wrong. A man of integrity would have owned up to the fact that he didn?t know what he was doing, and not kept guessing and spending my money. I gave him many opportunities to bail out, but he wouldn?t.

Once it?s back in my hands, I?ll see how I feel and what I do.

[Jagdpanzer]

Please let us know what solved the problem.


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[Erik]

Please let us know what solved the problem.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

I?ll start a new thread with the details.

[Atari_Prime]

Hi All,


I was reading over the thread and it kinda seems like my issues might be similar. So, I thought I might steal/borrow/pigtail off the discussion and see if we can adapt some of the comments for my circumstance.


I just bought a 94' ZR-1. Very low miles - 12,500. And only 3,000 of those have been in the last 20 years. I mention this because I fully expected a few issues on bringing her home.



First issue occured on first drive. Previous owner had never used full power mode. Like an idiot, the first thing I did was put the car in full power mode and drove home. It was only a 20 mile drive. About 3 miles into the drive I am merging onto a freeway and with my foot in the floor the car won't accelerate, rpms aren't going up either. And I'm only able to achieve about 40 mph. I decide to take it out of full power mode and few moments later she starts to behave like a normal car. I make it the rest of the way home without issue.


Two days later, after letting her idle in the driveway a bit and checking this and that, I put a bottle of injector cleaner in her and decide to give driving another try. Only about a 20 minute drive and for the most part everything goes fine. I used full power mode as well. And she had some pretty hard pulls shifting through the gears. I did notice though at stop lights, as I would let out on the clutch she wanted to die. I would have to rev to get her going. Also (and maybe unrelated my ABS and ASR lights came on). With these factors I decided to head home. When pulling into the garage she kept dying every time I would let out on the clutch. I had to give her some high revs to get her to move forward without dying. The service engine light came on while trying to park the car as well, but only after dying about 8 times trying to park the car.


Also of note, both times there was a smell. Definitely not gasoline. Kind of bitter. Reminded me somewhat of a clutch smell or burning electrical wiring. Some have contemplated this is the smell of the car running lean. I'm not sure. Of note though, during my short drive, the car recorded that I was getting 4 mpg. The smell went away but I can still get a slight wiff near the back of the plenum.


On the CorvetteForum I have received many suggestions, including: injectors, vaccum lines, fuel filter, bad vaccum sensor, o2 sensors, and stuck parking brake.



Often it is suggested I hook up an OBD1 scanner and check the codes. Don't have one. Looked at buying one, but none I can find seem to be able to do the job due to the 94' being OBD1 but also 16 pin. The OTC 3211 scanner was recommended and it seems like it might work, but it looks like it is no longer made and the only remaining ones are for sale at a premium. I am considering going the TunerPro route, but would like to get more data to see if a) this will get me all the same info, and b) I can use my existing laptop and just install some software.


It has also been suggested that I check the fuel pressure. Same situation, don't have a guage and honestly am not sure where to hook it up if I did. I think the OBD1 scan should tell me the fuel pressure though if I understand correctly.


Lastly, they suggest I change the fuel filter. Seems easy enough, if you have jack stands. I try to avoid going under cars when I can. I think this a simple fix that I may farm out to Corvette Mike or someone similar. It needs a new serpentine belt as well, so with some luck those two things could fix my problems.


At the end of the day, injectors is the number one comment, but I would like to avoid going there until absolutely necessary.


Would love to meet a friend in Orange County, CA who might be able to coach me through some of these items in exchange for some bourbon and bbq?


Thoughts and advice are welcome and appreciated.


Thank you.

[G8nightman]

Hi All,





I was reading over the thread and it kinda seems like my issues might be similar. So, I thought I might steal/borrow/pigtail off the discussion and see if we can adapt some of the comments for my circumstance.





I just bought a 94' ZR-1. Very low miles - 12,500. And only 3,000 of those have been in the last 20 years. I mention this because I fully expected a few issues on bringing her home.







First issue occured on first drive. Previous owner had never used full power mode. Like an idiot, the first thing I did was put the car in full power mode and drove home. It was only a 20 mile drive. About 3 miles into the drive I am merging onto a freeway and with my foot in the floor the car won't accelerate, rpms aren't going up either. And I'm only able to achieve about 40 mph. I decide to take it out of full power mode and few moments later she starts to behave like a normal car. I make it the rest of the way home without issue.





Two days later, after letting her idle in the driveway a bit and checking this and that, I put a bottle of injector cleaner in her and decide to give driving another try. Only about a 20 minute drive and for the most part everything goes fine. I used full power mode as well. And she had some pretty hard pulls shifting through the gears. I did notice though at stop lights, as I would let out on the clutch she wanted to die. I would have to rev to get her going. Also (and maybe unrelated my ABS and ASR lights came on). With these factors I decided to head home. When pulling into the garage she kept dying every time I would let out on the clutch. I had to give her some high revs to get her to move forward without dying. The service engine light came on while trying to park the car as well, but only after dying about 8 times trying to park the car.





Also of note, both times there was a smell. Definitely not gasoline. Kind of bitter. Reminded me somewhat of a clutch smell or burning electrical wiring. Some have contemplated this is the smell of the car running lean. I'm not sure. Of note though, during my short drive, the car recorded that I was getting 4 mpg. The smell went away but I can still get a slight wiff near the back of the plenum.





On the CorvetteForum I have received many suggestions, including: injectors, vaccum lines, fuel filter, bad vaccum sensor, o2 sensors, and stuck parking brake.







Often it is suggested I hook up an OBD1 scanner and check the codes. Don't have one. Looked at buying one, but none I can find seem to be able to do the job due to the 94' being OBD1 but also 16 pin. The OTC 3211 scanner was recommended and it seems like it might work, but it looks like it is no longer made and the only remaining ones are for sale at a premium. I am considering going the TunerPro route, but would like to get more data to see if a) this will get me all the same info, and b) I can use my existing laptop and just install some software.





It has also been suggested that I check the fuel pressure. Same situation, don't have a guage and honestly am not sure where to hook it up if I did. I think the OBD1 scan should tell me the fuel pressure though if I understand correctly.





Lastly, they suggest I change the fuel filter. Seems easy enough, if you have jack stands. I try to avoid going under cars when I can. I think this a simple fix that I may farm out to Corvette Mike or someone similar. It needs a new serpentine belt as well, so with some luck those two things could fix my problems.





At the end of the day, injectors is the number one comment, but I would like to avoid going there until absolutely necessary.





Would love to meet a friend in Orange County, CA who might be able to coach me through some of these items in exchange for some bourbon and bbq?





Thoughts and advice are welcome and appreciated.





Thank you.



Jump the pins with a paper clip you can get the codes


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[Atari_Prime]

Jump the pins with a paper clip you can get the codes


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)


Already did. Below are the codes, but of note on a 94' the ECM codes are not visible without a reader.


Module 1 - Central Control Module
C12 (normal, startup code)

Module 4 - Engine Control Module
H61

Module 9 - ABS/ASR Module
H58
H83

[DRM500RUBYZR-1]

OK.
Three times since you drove it home I have suggested you attempt to determine the source of the "Burning Smell" that you repeatedly stated on the other Forum.
You state the ABS /ASR light is on.
Kindly FIRST focus on finding out what is overheating to the point of creating a discernable odor.
If you burn the car up, it won't much matter why it also ran poorly before then.
You can lead a horse to water.........................
:cheers:
Marty

[G8nightman]

Read article

https://tech.corvettecentral.com/2011/01/c4-diagnostic-trouble-codes/


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[Matt B]

Your Code 61 indicates trouble in the Secondaries system, probably because there is a vacuum leak avoiding the ports to open properly. Is the vacuum pump (located in the very front right corner under the hood) running at startup for a few seconds and then cycling every few seconds? If not it may already be stuck or burnt, if yes and it keeps running there is a vacuum leak.
As far as the injectors are concerned you will find a good guide how to measure their resistance here: http://zr1specialist.com/HAT%20Web/articles%20index.htm
Marc's page is generally a great source of highly valuable information and so is Marc himself of course. You may consider his service to resolve your issues.
If your car shows injector issues these have to be resolved immediately as faulty injectors can cause a lot of trouble down the road.

Again, good luck!

Sent from my SM-G991B using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[Atari_Prime]

Your Code 61 indicates trouble in the Secondaries system, probably because there is a vacuum leak avoiding the ports to open properly. Is the vacuum pump (located in the very front right corner under the hood) running at startup for a few seconds and then cycling every few seconds? If not it may already be stuck or burnt, if yes and it keeps running there is a vacuum leak.
As far as the injectors are concerned you will find a good guide how to measure their resistance here: http://zr1specialist.com/HAT%20Web/articles%20index.htm
Marc's page is generally a great source of highly valuable information and so is Marc himself of course. You may consider his service to resolve your issues.
If your car shows injector issues these have to be resolved immediately as faulty injectors can cause a lot of trouble down the road.

Again, good luck!

Sent from my SM-G991B using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

Where did you find that code information? I haven't been able to find that anywhere. I found another post with someone who had the same code and couldn't find it either.

As far as start a procedure: If I turn on the car but not the ignition, there is a clunk coming from the front of the car. It cycles about every three seconds. For at least 25 to 30 seconds it does not stop. I don't know how long it would continue beyond that. I would compare the clunk noise to the dull cocking of a rifle.

[Atari_Prime]

OK.
Three times since you drove it home I have suggested you attempt to determine the source of the "Burning Smell" that you repeatedly stated on the other Forum.
You state the ABS /ASR light is on.
Kindly FIRST focus on finding out what is overheating to the point of creating a discernable odor.
If you burn the car up, it won't much matter why it also ran poorly before then.
You can lead a horse to water.........................
:cheers:
Marty

Hi Marty. While I will grant it as possible it could be brake related, based on other data it seems unlikely. If this helps, tonight I did a small test. Leaving it in valet mode I put it in reverse backed up a few inches without any issue and then put it in first and went forward a few inches without any issue. It behaved like a perfectly normal car. No attempt to die at all. Also those codes I mentioned only popped up during that one drive and have never popped up before or since that time. Granted, also I'm not using the brake that often sitting in the driveway. I have a pressure gauge arriving tomorrow. Provided I can find the Schrader valve which I understand to be next to the alternator I plan on doing a couple of tests. That may require me to go out for a drive. We'll see if those codes reappear. Also I'm contemplating going through the fuse panel and simply ripping out all the old fuses and replacing them with new ones just in case any of them are dead or dying. I can't think of any reason why that would be a bad idea. At the moment my strongest theory is that the secondary pump is failing and whatever issue is only occurring after the car gets into the higher RPMs under load or warmed up, or it's a simple as a clogged fuel filter. I don't have the equipment to change the fuel filter at home, I don't trust the nearby dealership to do it, and the mechanics I think I can trust can't get to it for several weeks. So there's that. Fun fun.

[Matt B]

Codes are in the shop manual (which I highly recommend) in the Central Control Module (CCM) diagnosis section (and in the article linked earlier). However I'm speaking about a 91, maybe it's different in your 94 case. In my case it was a faulty secondary vacuum selenoid and stuck check valve leading to an inoperable pump which in turn leads to a lack of vacuum at persisting WOT condition in high gear acceleration (4th+). Then the engine control sets a rev limit, too.
As said you can easily verify the correct vacuum operation by monitoring the pump (or pull the vacuum line off the pump and hook up a manually operated pump to see how well vacuum is held)

When your car is that low mile (like mine is, only 18.5k mls of which the last 1000 took 10 years) it's recommendable to first fully service everything and then carefully wake her up. I found a lot of issues, oil & vacuum leaks, defect sensors, selenoids, Stone Age fluids etc.

If the secondary system was never used it's very likely that the secondary intake section is packed with deposits and needs to be carefully cleaned by driving with secondaries active for an extended period. I just pulled my plenum to fix that defective selenoid and took the chance to inspect primary and secondary intake valves with an endoscopic camera. There is A LOT of deposits though they actually were used. Primaries instead a super clean.

Again, given that I just made the same experiences like you, I really recommend to work though the car first and then put load on her.

[Atari_Prime]

Codes are in the shop manual (which I highly recommend) in the Central Control Module (CCM) diagnosis section (and in the article linked earlier). However I'm speaking about a 91, maybe it's different in your 94 case. In my case it was a faulty secondary vacuum selenoid and stuck check valve leading to an inoperable pump which in turn leads to a lack of vacuum at persisting WOT condition in high gear acceleration (4th+). Then the engine control sets a rev limit, too.
As said you can easily verify the correct vacuum operation by monitoring the pump (or pull the vacuum line off the pump and hook up a manually operated pump to see how well vacuum is held)

When your car is that low mile (like mine is, only 18.5k mls of which the last 1000 took 10 years) it's recommendable to first fully service everything and then carefully wake her up. I found a lot of issues, oil & vacuum leaks, defect sensors, selenoids, Stone Age fluids etc.

If the secondary system was never used it's very likely that the secondary intake section is packed with deposits and needs to be carefully cleaned by driving with secondaries active for an extended period. I just pulled my plenum to fix that defective selenoid and took the chance to inspect primary and secondary intake valves with an endoscopic camera. There is A LOT of deposits though they actually were used. Primaries instead a super clean.

Again, given that I just made the same experiences like you, I really recommend to work though the car first and then put load on her.


I have read through the article prior, that's where the info about the ECM codes not being visible comes from. And I couldn't find code 61, strange.


A local club member had some simple advice for me that wasn't too far off of one of your recommendations. He said to put in some injector cleaner and go drive it for an hour at freeway speeds and then put another bottle and do it again.



Soon I am going to try to change out the serpentine belt. Hopefully won't be too difficult if I can figure out the tensioner.

[Atari_Prime]

I found some more codes, but not 100% sure they are correct for the year.



Some information indicates the following:


H58 (EBCM Assembly fault)

H83 (low brake fluid)


...what is an EBCM? Electronic Brake Control Module?


Anyway, going to check the fuses, and have the brake fluid flushed on Monday. Hopefully be able to pull more codes too with a reader. Maybe some tests will show what's up.

[DRM500RUBYZR-1]

It is exactly what I expected to be problematic.
THE EBTCM essentially pumps the brakes to avoid lockup in a panic stop and depending upon year, assists in traction control.
Your first two posts (although difficult to track due to multiple threads),
clearly stated that you sensed the brakes were on.
Congratulations, you were correct.
Change out the fluid using the procedure in the FSM doing so carefully.
I would also inspect or replace your brake hoses and carefully evaluate the performance of your master cylinder as well as the EBCM.
Hopefully overheated brake pads were causing your smell, which may also need to be replaced due to the overheating.
Again overheated clutch or brake linings have a distinctive odor.

Correct these things before moving on to engine performance issues.
Keep us posted on findings and progress.
Marty

[1991 Corvette ZR-1]

Where did you find that code information? I haven't been able to find that anywhere. I found another post with someone who had the same code and couldn't find it either.

As far as start a procedure: If I turn on the car but not the ignition, there is a clunk coming from the front of the car. It cycles about every three seconds. For at least 25 to 30 seconds it does not stop. I don't know how long it would continue beyond that. I would compare the clunk noise to the dull cocking of a rifle.

If this is still an issue, have someone key the car to on but not start and listen up front. The clunking noise you?re talking about could be one of the headlight motors. Whenever I disconnect the battery and need to reconnect the battery, the driver side headlight motor chatters for a second or two. A bad ground connection could be causing something similar for you. But for running as long as you say it is, it may be the vacuum pump on the front passenger side in front of the overflow bottle.