90 ZR-1 running bad.

[zr1nsxgto]

Hello folks. I have followed the ZR-1 Net for the last 16 years, but haven't contributed to much. I have a 90 ZR-1 with 7200 miles that is basically a brand new car. Over the last 18 months, I've only driven it 2 times and I have noticed a very bad miss/loss of power when you begin to aggresively open the throttle. It acts very similar to the air duct collapsing, but I put a insert in it immediately after acquiring it in 95. The #2 plug wire also has a split in it which has been there ever since I have had the car. I do have a new set of GM wires without the logos, but they have been in storage for 8 years. I also suspect there might be a plugged injector but am not certain as the problem is sporadic. When the engine is started cold, it runs great as it heats up. It continues to run very well after it gets fully warmed up until the engine is shut off. Then if you restart the engine hot, it stumbles and misses badly when you try to open the throttle. Shut if off, let it cool, and all is good again.

I do have good wrenching skills and am not afraid to work on the LT-5, but I'm no expert. I do work for Tony Stewart Racing and don't get too much free time to play with my cars. I have thought about maybe having Haibeck go through this car a "tune" it. I'm sure there are other issues that are age related. He probably has seen these symptoms a gazillion times and knows exactly where to start. I could well chase the problem for a while before correcting it. Any good suggestions would be appreciated.

[ZZZZZR1]

hey there,


Likely you have bad injectors... There are many threads on that procedure with pictures and you could get a video from Haibeck himself (www.zr1specialist.com (http://www.zr1specialist.com)).

The one thing we say to owners is you have to drive the car so you don't get issues. Not just starting it once a month, but opening up the secondary injectors.

Things to change out are the injectors and fuel filters... That is a good start and "should" fix your issue. Spark plug wires can be tested once you have the plenum off and you can check your coil pack too. (coil packs are $155 for the set and injectors / gaskets are under $500)

Get your gaskets from www.jerrysgaskets.com (http://www.jerrysgaskets.com) (very reasonably priced) Coil packs are on ebay and the injectors are bosch.

Keep us updated

:cheers:

David

[Kevin]

doubt its the coil packs, though if nothing else works it could be this. What you want to do is check the resistance of the injectors with an ohmmeeter I think Gordon said anything under 12.5 ohm was not good. Not driving these cars kills them

[zr1nsxgto]

As soon as I submitted this thread, I went to Marc's website and also checked a variety of sources regarding the GM injectors used on the early ZR-1's. Very prone to coil breakdown when hot. I've always suspected that the injectors in my car were not perfect, but I drive this car so rarely that I've just never took the time or the dollars to remedy the mis-fire. I just recently re-juvinated my interest in this car and now have to commit to getting it running reliably again. I think I'll start to pull the plenum and do the injectors and plug wires. I just hate to have the "incorrect" wires on my car because it's as pristine of a 90 ZR-1 as any I have ever seen in the last 6-8 years. I think that's why I'm beginning to renew my interest in it.

[Kevin]

there's only a handful of people who will know the wires aren't right, if it really bothers you I may have a set kicking around I can let go of. The ethnol in the gas today is what kills the injectors I've had to replace mine...in BG...in the NCM lot....after driving down from pa on 6 cylinders. It was like driving a washing machine, bloody awful.

[vettn71]

Jon Banner of FIC built a set of Delphi injectors for my NCRS car that are not wet-coil design. They work great and look just like the originals. I'd give Jon a call - he's a great guy who will work with you to get what you want

Jim

[zr1nsxgto]

What are the preferred injectors today. RC were always very hightly recommended, and I also saw a listing for a GM clone injector set for the LT-5 for $550 (approx). I'm not to concerned about the pricing as much as I'm concerned about original appearance. Of course, you can't really see the injectors anyway so I guess performance vs. price is what I'm looking for.

By the way, thanks for the replys!

[ZZZZZR1]

RC's are the best, but pricey....

Bosch seem to do the job and VERY reasonably priced.

[tomtom72]

Hello & welcome to our asylum!:hello:

I would tend to agree with the fuel vapor lock theory.....fwiw:o

I just this year swapped out my original fuel pumps. They didn't stop working, and they were within the PSI limits in the FSM albeit on the lower end of the scale.....but I had new pumps sitting in inventory so I figured why not? After all they were 20 yrs old. I could see the difference on the KOEO PSI test and feel it in my butt dyno.

I'm not saying just buy new pumps, but I might say do the KOEO fuel pump test from the FSM diagnostic section.

Put some tape on that cracked wire just as a temp measure so you don't have any stray spark jumping around to complicate your life. Then I would ohm out the coil and wire combination and see what might be up with the 20 year old ignition equipment....just to cover all the bases.;)

Also, I would add a word about the OE injectors. Their failure pattern is similar to your stated symptoms, but they get progressively worse in that the coil shorting starts at shorter time frames as they degrade further. Eventually the coils get so bad the miss is seen at cold start up. I would not argue against replacing the OE injectors as a maintenance item because it truly is a "When" and not "If" that the alcohol attacks their coils.

:cheers:
Tom

[zr1nsxgto]

Thanks for all of the replys so far. I am leaning heavily towards faulty injector issues with the symptoms my car has. It could possibly be a vapor lock issue, but to be honest, I have never heard of a vapor lock issue on fuel injected engine without some other obvious issue causing extreme under hood temperature. I think my first attack is going to be pulling the plenum, replacing all of the injectors, verifying ingnition coil impedance, and checking out the plug wires. If anyone has a #2 wire available, I'd be interested in it.

It might be a month or two before I tackle this project, but I certainly will respond to this list and let you know what happens. This car is just about perfect in every way other than the misfire and needs to be corrected. I just need to make a decision on what injectors to use. Because I keep this car garaged 99.9% of the time, I'm leaning towards RC injectors. Will do more research and questioning.

[ZZZZZR1]

Take a look at this thread (thanks to Michael R)

http://www.zr1.net/forum/showthread.php?t=7614&highlight=plenum+pull+michael

[tomtom72]

Sorry to sound like I can't make up my mind, but I'm asking myself if the injectors could leak after they get hot? That would make a hot restart problematic, a flooded motor doesn't run well.

Stupid question, how long between fuel filter changes? I'm thinking that the coils didn't fail yet due to alcohol. I'm looking for something that would make a car run badly after a hot restart.

Any other electrical component that would suffer from heat exposure, like injector and or ignition coils, would become progressively worse over time. This doesn't seem to be supported by your description of your car's symptoms.

If you have a scanner I'd hook it up and do a hot restart, maybe it would tell you something. Or after a hot restart and the miss returns stand behind the car and smell the exhaust. If it smells lean, not enough fuel, injector coils are top on my list. If it smells rich, something is not lighting the fire ( ignition system has to be the suspect?) or something is providing too much fuel ( dirt in the fuel system?).:o

:cheers:
Tom

[A26B]

First: Are you getting an SES light? Are there any stored codes? If so, make note of them, disconnect the battery for a minute or two, then drive the care again to duplicate the problem. Recheck for stored codes. Research stored codes & proceed.

Given that it misses badly after a hot re-start, after eliminating "air" you should be able to identify whether "spark" or "fuel" with no special tools in about 30 min.

The basics:

1. Engine running, pull each plug wire. Noticable difference, cylinder fire OK. No difference, miss cylinder identified.

2. Engine off, pull 1 plug wire, insert spare plug, lay on plenum. Start engine, gradually increase gap from plug to plenum (or engine ground). Good spark = blue 3/4" to 1" jump. Weak spark = orange. Weak spark either wire or coil. DO this procedure for each cylinder. If 2 dead cylinders & they are "paired" cylinders, definitely bad coil.

3. If steps 1 & 2 check OK, high probability of fuel injector on cylinder with no noticable change in miss as identified in step 1. Given it's a 90 model and the propensity of injector failures in 90~92 LT5's, I would replace the entire set. Be sure to replace all fuel system o-ring seals while you're in there. Those seals are now over 20 years old. All fuel injector upper and secondary lower o-ring seals (should be Viton) come with new injectors. You will need the lower primary seals, fuel feed & return block seals & the fuel rail pipe & regulator seals.

Here's a tech reference for the lower primary seal replacement.
http://jerrysgaskets.com/store2/root/index.php?main_page=product_info&cPath=13&products_id=446

In any event, replace wire #2 at minimum. I looked in my spare wire pile but do not have a #2. Sorry.

[zr1nsxgto]

Are the primary and secondary injectors (RC) the same injector? Every injector that I have researched has a separate part # for the primary and secondary. I'm going to try to use my employment here at Tony Stewart Racing to get a reasonable deal on a full set of injectors.:)

[WydGlydJim]

The car is rebelling from under use, and not enough 7k RPM blasts!
;)

More than likely injector as most have concurred. I wouldn't suspect any ignition problem with that low of miles, but it is always possible. Only sure way to tell is to put it on an engine analyzer. I'd change the plugs, and you can probably tell which one is not firing well, and then you can just check that one ignition path to make sure it is getting spark to the plug. If it is getting nice hot spark, then injector more than likely. I believe the primary and secondary injectors are always different across manufacturers
:thumbsup:

[zr1nsxgto]

Actually, we have a variety of sources for injectors here at TSR, but I'm not sure if they would have a suitable injector. FAST is a company that has injectors for the ZR-1. Has anyone tried them?

[zr1nsxgto]

Just ordered injectors from John Banner at FIC. We'll see what happens. Need to send e-mail to get gasgets from Jerry?

[Paul Workman]

Vapor lock could occur down on passenger side near fuel filter which is near exhaust manifold for example. Keep us posted on what you find as a solution. :thumbsup:

I'm dubious w/ regard to vapor lock for a couple reasons:

1) Vapor locking, in the sense of the fuel pump loosing its prime, pretty much went away with in-tank fuel pumps and hot fuel return (to the tank) lines (since deemed unecessary and dropped from use on the LSx engines, no?)
2) But, even if you're referring to vapor that might form in a heat-soak situation near the exhaust, the Reid vapor pressure (http://en.citizendium.org/wiki/Gasoline#Vapor_pressure)at 100*F is only around 7#. Tho vapor pressure is not linear; exponental with a change in temperature, in fact. Not sure what it is at say 200*, but I doubt it is anywhere near normal pressure when the switch is turned on. At 45-50 psi (switch turned back on) I'm betting any vapor resulting from heat and pressure leak-down would immediately revert to a liquid.

I'm going to keep looking for some difinitive answer to the vapor pressure question, but I'm betting it is electronics failure (injector coils?) as a function of heat soak.

Just my 2 cents...

P.

[zr1nsxgto]

I agree with you Paul. The info you wrote about is why I can't ever recall/or heard of a "vapor lock" in a modern day electronic fuel injected engine. Don't have any real engineering data to dispell the possibility of vapor lock however.

[Kevin]

Just ordered injectors from John Banner at FIC. We'll see what happens. Need to send e-mail to get gasgets from Jerry?

jerry is good people, met him in BG a few years ago. can't think of another person I'd order from other then him

[Dynomite]

I'm going to keep looking for some difinitive answer to the vapor pressure question, but I'm betting it is electronics failure (injector coils?) as a function of heat soak.

Just my 2 cents...

P.

If it were some electronics failure as a function of heat soak, would not the problem exist under the conditions of a hot engine just before it is shut off?

"When the engine is started cold, it runs great as it heats up. It continues to run very well after it gets fully warmed up until the engine is shut off."

Or......some electronic component heats up just a bit hotter immediately after engine shut down (normal as the vehicle is not moving and coolant is not circulating and those parts that are normally hotter than average engine operating temperatures then heat soak to a higher temperature adjacent electronic parts) such that the electronic parts (or other parts) are then in temporary failure.

If you then start the engine up shortly thereafter the electronic part (or other part) is still in failure untill such time the temperature of the electronic part gets back down to "cold" at which point the electronic part mends itself and is good to go up to normal engine operating temperatures.

Then if you go above those normal engine operating temps temporarily at engine shut down you have the part failed again :confused:

[tomtom72]

Just ordered injectors from John Banner at FIC. We'll see what happens. Need to send e-mail to get gasgets from Jerry?

You can use the link in Jerry's signature. Or click on this link!:)

http://jerrysgaskets.com/store2/root/

Jerry is Da Man!

:cheers:
Tom

[zr1nsxgto]

Just ordered gasgets and o-rings from Jerry. Getting all the stuff together. Now just have to order some time! That's going to be the part that gives me trouble.:icon_scra

[erikszr1]

If it were some electronics failure as a function of heat soak, would not the problem exist under the conditions of a hot engine just before it is shut off?

"When the engine is started cold, it runs great as it heats up. It continues to run very well after it gets fully warmed up until the engine is shut off."

Or......some electronic component heats up just a bit hotter immediately after engine shut down (normal as the vehicle is not moving and coolant is not circulating and those parts that are normally hotter than average engine operating temperatures then heat soak to a higher temperature adjacent electronic parts) such that the electronic parts (or other parts) are then in temporary failure.

If you then start the engine up shortly thereafter the electronic part (or other part) is still in failure untill such time the temperature of the electronic part gets back down to "cold" at which point the electronic part mends itself and is good to go up to normal engine operating temperatures.

Then if you go above those normal engine operating temps temporarily at engine shut down you have the part failed again :confused:
i had the same exact problem as this, i did full tune-up, plugs, wires and coils and it ran the same, then....i cleaned injectors, fresh tank of "summer gasoline" and a techtron fuel additive and the problem went away the next day when i took it to work.....really! i would of swore this would never be this simple. i was ready to do injectors....so far so good... im believing what you said...very possible:-D