New Accel Injectors, same problem different hole.

[tccrab]

I replaced my fuel injectors because I came up with a miss at lower RPMs, diagnosed primary fuel injector failure, and after measuring them with a volt meter, one was obviously bad and two others were on their way.
Put in the new Accels with the special 'O' rings from Haibeck. Installation was a breeze and everything went back together just as it should. To be honest, I was just a little worried, my first plenum pull and all.:rolleyes: :pray
Engine fired right up and became obviously clear that I still had a miss.
Before, cylinder 3 was not firing, pulling it's spark plug wire when idling did not make the idle worse.
Now cylinder 5 does not fire.
Got spark, have ohm'ed the fuel injectors and they're fine, and I don't have a connector that's not seated.
No big obvious vacuum leaks, the secondaries hold vacuum and the idle however rough is under 1000 rpms, so I'm fairly certain it's not a leak.

The miss seems to go away when the secondaries open. Under hard acceleration the motor smooths out and the miss appears to go away.

Taking off from a stop is almost painful, the miss is that obvious. It's not an occasional misfire, it's a dead hole.

I've not yet pulled the sparkplug, this cylinder was firing prior to the fuel injector replacement, and the spark plug wires were replaced by the P.O.'s mechanic.
The motor has 10,800 miles.

I'm playing with the idea of pulling the plenum back off and taking that fuel injector down to the local speed shop to get it flowed. Even though it's coil measures fine, it might have junk in it.
I'd like to have a few more diagnostic tools under my belt before I go yanking the plenum.

Guys, got any hints, helps, ideas, WAG's?
ANY help at all right now would be SINCERELY and thoughtfully appreciated.

TomC
'90ZR1 #792

[Jeffvette]

Did you happen to remove the spark plug wires for the coil packs while you were under there.

Also how strong is the spark at the plug?

[tccrab]

Jeff:

I didn't mess with the spark plug wires at the coil packs.
It was actually pretty clean under the plenum, all things considered.
Spark seems OK, don't have any real way of testing them, I don't want to fry my DVM.
I was going to check at the local auto parts store for some kind of tester.

TomC
'90ZR1 #792

[RZR]

I found this thread and had to register to reply ASAP. I too am in the same exact dilemna as tccrab. I have replace the primaries with Accels, checked connectors, plugs, etc. same steps tccrab performed and yet have a consistent miss during normal driving. I have logged data using Datamaster and have definitely found a lean condition on the left side based on long term and short term fuel trims. ALSO, significant knock counts occur during higher MAP sensor readings. Spark plugs confirm the lean condition. I would be VERY interested to hear any suggestions at this time and wuold be happy to share anything I find. Interesting thing is WOT does not produce knock counts but does show a slightly lower 02 voltage reading for the left side.

[tccrab]

I found this thread and had to register to reply ASAP. I too am in the same exact dilemna as tccrab. I have replace the primaries with Accels, checked connectors, plugs, etc. same steps tccrab performed and yet have a consistent miss during normal driving. I have logged data using Datamaster and have definitely found a lean condition on the left side based on long term and short term fuel trims. ALSO, significant knock counts occur during higher MAP sensor readings. Spark plugs confirm the lean condition. I would be VERY interested to hear any suggestions at this time and wuold be happy to share anything I find. Interesting thing is WOT does not produce knock counts but does show a slightly lower 02 voltage reading for the left side.

RZR:

I'm sorry to hear that we're in the same boat.

I've called around to a few of the ZR1 tuners and i've got a few more simple tests that I will be performing to hopefully diagnose my failure. Just want to share them with you in the hopes that you havn't tried them yet.

First thing I'm going to do is to see if the connector on my dead hole's primary fuel injector is not seated properly. Mark Haibeck (thanks for the tips!) suggested fashioning a hook with a strong piece of wire (coathanger) and try to pull the connector off. There's just enough room to do this without pulling the plenum. If the connector moves, then it's not seated properly and could be the culprit. I don't give it much hopes for success as I've already ohm'ed the injectors at the ECM and my bad one ohms correctly, but you never know....
Next, I will go down to the auto parts store and buy a in line spark plug tester like this one:
http://www.drivewerks.com/catalog/shopcart/TOOL/POR_TOOL_CAT450_pg6.htm
This will help in determining if I'm getting the same amount of spark at the plug on the dead hole vs. all the rest. (Thanks Mike Ebert @ ESS)

If still no joy, the plenum comes off.

Next thing to check is to see if the primary injector is spraying. With the plenum off, turn the ignition on, this will cause the fuel pumps to pressurize the system and energize the fuel injectors with 12 volts. Then ground the appropriate pin at the yellow connector (Connector A, pin 3 which is the primary injector on cylinder 5, my dead hole) on the ECM. This will cause the injector to spray, as the ECM controls the fuel injector by opening and closing the ground ciruit. This can be done without taking the injectors out, just look down the primary hole while having somebody ground the appropriate pin on the ECM connector.
If no spray, then injector is at fault, unless there's no 12v at the injector, then the ECM or wiring is at fault.
If it sprays, then ignition most likely culprit, although it could still be ECM.
(thanks Mark Haibeck)
In my case, I'm hoping for just a bad connection on the injector plug, but more likely it's the injector itself.
I don't even want to think about having a bad ECM...:pray :pray

TomC
'90ZR1 #792

[RZR]

Tom, thank you very much for the detailed action steps for further diagnosis, I will monitor the thread for your progress. I have not tried ohm'ing the injectors via the ECM and am not sure which specific hole is misfiring as there is not one spark plug with the telltale signs of a no-fire condition. Can you please point me towards a 'how to' on this procedure? I do not currently have an ECM pin reference. I am beginning to really miss the ZR1's normal performance..........:cry:

[Jeffvette]

Where are you in Washington?

[RZR]

Hi Jeff,
Seattle. How about you?

[Jeffvette]

Battle Ground, I was up in Seattle this past weekend though. Met up with a few other ZR-1 guys.

Dropped a part off for another ZR-1 guy to test on his car.

Check out www.pnwzr1.net

[tccrab]

Tom, thank you very much for the detailed action steps for further diagnosis, I will monitor the thread for your progress. I have not tried ohm'ing the injectors via the ECM and am not sure which specific hole is misfiring as there is not one spark plug with the telltale signs of a no-fire condition. Can you please point me towards a 'how to' on this procedure? I do not currently have an ECM pin reference. I am beginning to really miss the ZR1's normal performance..........:cry:

In my case it was easy to find the dead hole, I just fired her up and got her to operating temp. Then you just pull one plug wire at a time and listen for the engine to stumble. Because of how well the engine is balanced, cylinders 3,4,5 & 6 don't cause all that much imbalance if they're not firing, so you have to listen carefully when pulling the plug wire. It might take two or three go arounds to home in on the bad cylinder. The key is that when you pull the plug wire on the bad one, the engine sounds exactly the same.

I'll scan and .JPG the appropriate electrical diagram page from my Helms manual later today or early tomorrow morning.
It's pretty easy to measure the injectors at the ECM. All you need is a DVM with fairly long leads.
Remove the negative battery cable. Open passenger door and remove the INJ fuse, it's a yellow 20A, top row about halfway across. Remove the "A" connector on the ECM, it's the yellow one closest to the outside drivers side. Using your DVM, measure between the correct pin on the ECM (don't have the Helms book here at work, otherwise I'd list them) and the right hand side of the INJ fuse connector. Just stick your black probe from the DVM into the INJ fuse hole that is closest to the firewall, make sure it's got good contact.
My probes were too big to fit into the pin holes yellow connector on the ECM, so I cut a 2 or 3 inch piece of 3/32 wire to stick into the pin hole, then I could clip the Red lead of my DVM to it.
The actual ohms read from the ECM connector will vary depending on temperature and wire resistance. If you were to have measured at the fuel injector itself, the Ohms at room temperature should be 13+/-1 ohm.
What you are looking for is a variance between injectors, it'll be obvious if you've got a bad one or one out of spec.
No ohms at all would indicate a bad connection or a shorted coil in the injector.
Low or high ohms indicate coil failure in the injector itself.

Good luck!
Keep me posted!

TomC
'90ZR1 #792

[tccrab]

Hi Jeff,
Seattle. How about you?

RZR:

If Jeff offers to help, DO NOT turn the offer down.

Jeffie's THE MAN.:thumbsup:

I wish he lived a little closer to me.......

TomC
'90ZR1 #792

[Jeffvette]

I found this thread and had to register to reply ASAP. I too am in the same exact dilemna as tccrab. I have replace the primaries with Accels, checked connectors, plugs, etc. same steps tccrab performed and yet have a consistent miss during normal driving. I have logged data using Datamaster and have definitely found a lean condition on the left side based on long term and short term fuel trims. ALSO, significant knock counts occur during higher MAP sensor readings. Spark plugs confirm the lean condition. I would be VERY interested to hear any suggestions at this time and wuold be happy to share anything I find. Interesting thing is WOT does not produce knock counts but does show a slightly lower 02 voltage reading for the left side.

How do your O2 readings look. Fluctuate rapidly? Or stagnate? Remember at WOT the O2's are bypassed. The motor is just dumping fuel, which would mask all the issues you are talking about.

[RZR]

Tom, thanks a whole lot for that info. I will do the plug test again tonight. You're right, I didnt notice it the last time I tried that approach as I could not tell whether the idle was changing after pulling the plug wires. BTW, on another topic, I was wondering if you heard of or are experiencing this. After warmup I am getting a good puff of white smoke out the passenger-side exhaust when accelerating normally from a stop. No oil smoke after that even at WOT. My ZR1 is at 58k miles. I bought it with 25k and can remember this condition ever since. Car runs strong and compression checks out so I am guessing a valve seat perhaps (HOPE NOT!). Thanks again for all your feedback, I was losing hope doing searches on the internet when I finally saw your thread here.
Ray

[RZR]

Wow, and I thought I was all alone here amidst a sea of C5's, Z06's and C6's! Thanks for forwarding the PNWZr1 site. It is really nice to know there are other ZR1 enthusiasts out here. Some of those Z's in the photos look F A S T. Mine is bone stock except for a DRM chip.
Ray

[RZR]

How do your O2 readings look. Fluctuate rapidly? Or stagnate? Remember at WOT the O2's are bypassed. The motor is just dumping fuel, which would mask all the issues you are talking about.
Closed loop 02's fluctuate at the normal rapid rate between 100 and 900mv's. The WOT 02 voltages were different between right and left banks however. Left was mid 800mv's where right bank showed above 900mv's. If my memory serves me right I believe the lower WOT voltage represents a leaner condition. I am assuming that this is because one of the primary injectors is failing on that side. What do you think???
Ray

[RZR]

RZR:

If Jeff offers to help, DO NOT turn the offer down.

Jeffie's THE MAN.:thumbsup:

I wish he lived a little closer to me.......

TomC
'90ZR1 #792
You know, it is an absolute luxury to live anywhere near other ZR1 enthusiasts. I have not experienced that since I bought my ZR1 up until Jeff forwarded the PNWZr1 website link.=D>
Ray

[tccrab]

After warmup I am getting a good puff of white smoke out the passenger-side exhaust when accelerating normally from a stop. No oil smoke after that even at WOT. My ZR1 is at 58k miles. I bought it with 25k and can remember this condition ever since. Car runs strong and compression checks out so I am guessing a valve seat perhaps (HOPE NOT!). Thanks again for all your feedback, I was losing hope doing searches on the internet when I finally saw your thread here.
Ray

Ray:

'90 & '91's don't have valve stem seals, they didn't seem to think that they were needed.
Your little puff 'o smoke is probably just a little oil seeping down the valve stem.
Nothing to worry about unless it gets out of hand.


TomC
'90ZR1 #792

[RZR]

Thanks Tom. I sensed it wasnt a major problem but it is certainly an ego crusher when you pull off from a light and you dump a smelly little oil cloud on the nice folks admiring the fat 11-inch-wide rubber. :-({|=
Ray

[tccrab]

Thanks Tom. I sensed it wasnt a major problem but it is certainly an ego crusher when you pull off from a light and you dump a smelly little oil cloud on the nice folks admiring the fat 11-inch-wide rubber. :-({|=
Ray

Ray:

The trick is to leave so much tire rubber that they can't see the little puff of oil smoke. :thumbsup:

TomC
'90ZR1 #792

[RZR]

Tom,
One other issue related to the failed injectors I experienced and wanted to see if you experienced the same. When my primary injector(s) failed, the car mis-fired, bucked and kicked pretty good - I thought I had broken the motor. Shortly afterwards I pulled over, shutdown and noticed what sounded and smelled like a catalytic converter meltdown - loud ticks and a lot of heat from the underside. A few days later I heard clunking sounds from underneath the car during idle and low speed driving. I assumed this to be pieces of the cat dispersing within the exhaust system. I am planning my approach to solving this but thought I'd run it by you to see what you did if anything. I thought about just replacing the cats but now am faced with the possibility of a blocked muffler as well.
thanks,
Ray

[RZR]

Ray:

The trick is to leave so much tire rubber that they can't see the little puff of oil smoke. :thumbsup:

TomC
'90ZR1 #792
I LIKE IT!! Great suggestion and you know, with Sumitomo's being $107 a pop for the 17x11's, I can light 'em up at every stop!!

[tccrab]

I LIKE IT!! Great suggestion and you know, with Sumitomo's being $107 a pop for the 17x11's, I can light 'em up at every stop!!

Boy was I glad to see the price on the Sumitomos.
I've got a complete set of GoodYear GSC's on my Z and I was deathly afraid of having to replace them earlier than the usual 10,000 miles.

TomC
90ZR1 #792

[tccrab]

Tom,
One other issue related to the failed injectors I experienced and wanted to see if you experienced the same. When my primary injector(s) failed, the car mis-fired, bucked and kicked pretty good - I thought I had broken the motor. Shortly afterwards I pulled over, shutdown and noticed what sounded and smelled like a catalytic converter meltdown - loud ticks and a lot of heat from the underside. A few days later I heard clunking sounds from underneath the car during idle and low speed driving. I assumed this to be pieces of the cat dispersing within the exhaust system. I am planning my approach to solving this but thought I'd run it by you to see what you did if anything. I thought about just replacing the cats but now am faced with the possibility of a blocked muffler as well.
thanks,
Ray

Ray:
OMG, it must have been AWFUL.
My experience with failed injectors was nothing like that.
I took Girlfriend (that's what my wife calls my Z, for obvious reasons...:rolleyes: ) for a drive to a buddy's house about 25 miles up the mountain.
When I went to leave about half an hour later, it started fine, but I noticed a slight miss as soon as I pulled out onto the road. By the time I got home it was missing big time, at idle you could hear the dual mass flywheel rattle and you could feel the engine shaking the car.
I didn't drive it after that, was too afraid of hurting her more than she already was.

TomC
'90ZR1 #792

[tccrab]

Well, think I found it.
Check out these two pics, the first is Cylinder 8's fuel injectors, the second is Cylinder 6 (my dead hole).
The image might be too small to see the detail, but I won't know until I submit the post, so here goes.
Think this is my miss?

Hint: it's something to do with the secondary injector.

TomC
90ZR1 #792

[RZR]

INTERESTING! So that one injector in cylinder 6 looks like it isnt seated all the way. But if it is squirting fuel, will that make for a complete miss? It would make sense though since more air is being introduced into the cylinder so it should feel like a miss - I am just thinking out loud here.....
Tom, I would be really happy for you if thats all you have to do to fix it. I will then cross my fingers and hope to find the same situation in my car.:pray
GOOD LUCK and I cant wait for your next report after you push that baby in all the way!
Ray

[tccrab]

INTERESTING! So that one injector in cylinder 6 looks like it isnt seated all the way. But if it is squirting fuel, will that make for a complete miss? It would make sense though since more air is being introduced into the cylinder so it should feel like a miss - I am just thinking out loud here.....
Tom, I would be really happy for you if thats all you have to do to fix it. I will then cross my fingers and hope to find the same situation in my car.:pray
GOOD LUCK and I cant wait for your next report after you push that baby in all the way!
Ray

Ray:

Thanks!
I think whats happening is that the 'O' ring is actually pushed up out of the seat on the injector and just barely setting in the top of the injector hole. It's letting in gobs of air and throwing the air/fuel mixture way lean. So lean that the spark plug can't ignite the mixture until the secondary injector kicks in and squirts in gobs more gas.

It's as good a theory as any, I'm going with it.
Tomorrow after work I'll yank that fuel rail and replace the 'O' ring on that fuel injector and button 'er back up.
:pray :pray :pray

Wish me luck! :cheers:

TomC
'90ZR1 #792

[tccrab]

Well, getting closer.
#6 firing just fine now.
Idle is much smoother.

trouble is, now it's clear that #4 & #7 aren't firing all that well, and guess what? They're both on the same coil pack.

Need to figure out how to diagnose coil packs or sensors or wires.

Ideas?

TomC
'90ZR1 #792

[RZR]

Tom, really sorry to hear that you're still having issues. Not sure how to check coils/wires other than checking for a good spark while cranking. Are there any misfire codes? Not sure if you have a means to data log your car but I believe there is a way to check for any DTC codes thrown by the ECM. If so all it might tell you is that you have a misfire and you already know that. Really hope you get to the bottom of this as I bet its getting rather frustrating. I know, I have been in that spot recently and still kinda there.....

[tccrab]

Tom, really sorry to hear that you're still having issues. Not sure how to check coils/wires other than checking for a good spark while cranking. Are there any misfire codes? Not sure if you have a means to data log your car but I believe there is a way to check for any DTC codes thrown by the ECM. If so all it might tell you is that you have a misfire and you already know that. Really hope you get to the bottom of this as I bet its getting rather frustrating. I know, I have been in that spot recently and still kinda there.....

Ray:

Actually, it's not so bad.
I've learned a lot and by the time I have the plenum off and back on for the third time I hope to be pretty good at it. :dancing

I'm beginning to think that I had two problems, one obvious, which was bad/going bad fuel injectors, and a more subtle problem being a weak spark on cylinders 4 & 7.
The coil or sensor or whatever is causing the weak spark has probably been going on for quite a while and I just never noticed that the power was a few percent down. I have never raced Girlfriend, just an occasional first gear through third gear "back road boogie" to blow out the carbon and feel the power. Otherwise I drive it like a regular car, which may be part of my downfall. From all I've read, the harder you drive these cars, the better they perform.
When the fuel injector went, it caused a big miss, and coupled with the other two cylinders not firing well made Girfriend shake and rattle like a wet dog.

Now to find out about coil packs and what makes them work. There's gotta be some way to nail down either the coil pack or the electronics that drive them, sensors, etc. Time to dig through the archives...


TomC
'90ZR1 #792

[tccrab]

It was a dark and stormy night...
Oh, wrong story.
Saga of the mystery miss continues...


With the engine cold I've checked the coils at the plugs and they read:
1/6 = 19.68k Ohm
2/3 = 19.91k Ohm
4/7 = 18.05k Ohm
5/8 = 17.92k Ohm

I bought one of those little inline spark test lights and the glow is no different between cylinders.

Yet I clearly still have a miss, and pulling plug wires one at a time with the engine idling STRONGLY suggests that #4 & #7 aren't firing.

I've manually tested each primary fuel injector and verified BY SIGHT that each primary fuel injector squirt gas into each cylinder when I ground the appropriate pin at the ECM connector. (thanks for that NIFTY tip Mark Haibeck).

I've verified that the circuit to each primary fuel injector is continious and each injector coil measures +/- .2 ohms of each other.

No vacuum leaks, the engine idles at 500-600 when warm, but it's clearly not hitting on all 8.

Is there an easy to tell if the ECM is causing the fuel injectors to fire without using a scope?

Am I missing something?

HELP!

TomC
'90ZR1 #792

[tccrab]

ECM was bad.
Plugged in a replacement ECM kindly loaned to me from a fellow Forum member and she idles like a kitten and roars like the beast that she is.

I'm guessing that the bad fuel injectors in some way dragged down the injector drivers and caused some electronic component to fail.

Whatever.

Problem has been solved.
Now to find a new ECM.
Anybody got leads on new ECM's?
Not sure I want to go with a rebuilt unit, but will have to see if any are available.

TomC
'90ZR1 #792

[Tom]

I wouldn't be concerned about a rebuilt unit. My 1990 ZR-1 ECM was replaced under warranty with a rebuilt unit in late 1994 and it is still working.

I would ask a local dealer where they send instrument clusters and radios for warranty repair and see if that place can rebuild your ECM. Here in southern California I would talk to AER (Auto Electric Radio), 1841 West Commonwealth, Fullerton, CA, 92633, 714-871-7357, 800-321-6970.

[tccrab]

I wouldn't be concerned about a rebuilt unit. My 1990 ZR-1 ECM was replaced under warranty with a rebuilt unit in late 1994 and it is still working.

I would ask a local dealer where they send instrument clusters and radios for warranty repair and see if that place can rebuild your ECM. Here in southern California I would talk to AER (Auto Electric Radio), 1841 West Commonwealth, Fullerton, CA, 92633, 714-871-7357, 800-321-6970.

Tom:

Appreciate the input.
New ones are no longer available, however GM does offer a rebuilt unit w/exchange.
GM part #: 16196394, $149 list price from local dealer.
www.GMPartsDirect.com has 'em for $77, no response when I emailed and asked for an estimated delivery date as it's not a stocked item.
www.ZipCorvette.com, $95.95, but you've got to send yours in for rebuild, wonder how long that would take?
There's an eBay auction for a NOS '90 ECM, but I think $389 is just a little steep...

My local dealer gave me a 10% discount and should have it tomorrow. It was worth the few extra dollars for the peace of mind.

TomC
'90ZR1 #792

[1990 quasar blue]

https://www.partszoneonline.com/index.php
86.00 without the pound of flesh shipping charges. They're pretty good to deal with as well.