90 ZR-1 running bad. - ZR-1 Net Registry Forums

zr1nsxgto · 07-10-2010

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 · 07-10-2010

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).

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 (very reasonably priced) Coil packs are on ebay and the injectors are bosch.

Keep us updated

David

Kevin · 07-10-2010

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 · 07-10-2010

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 · 07-10-2010

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 · 07-10-2010

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 · 07-10-2010

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 · 07-10-2010

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

Bosch seem to do the job and VERY reasonably priced.

tomtom72 · 07-11-2010

Hello & welcome to our asylum!

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

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.

Tom

zr1nsxgto · 07-11-2010

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.

07-10-2010	#1
zr1nsxgto Join Date: Apr 2007 Location: Greenwood Indiana Posts: 50	90 ZR-1 running bad. 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.

07-10-2010	#3
Kevin Join Date: Jun 2005 Location: pittsburgh Posts: 4,624	Re: 90 ZR-1 running bad. 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 __________________ It's not the car, it's the people - Doug Johnson 90 r/r "KEYS ON" nick named "T.L.B"

07-10-2010	#4
zr1nsxgto Join Date: Apr 2007 Location: Greenwood Indiana Posts: 50	Re: 90 ZR-1 running bad. 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.

07-10-2010	#5
Kevin Join Date: Jun 2005 Location: pittsburgh Posts: 4,624	Re: 90 ZR-1 running bad. 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. __________________ It's not the car, it's the people - Doug Johnson 90 r/r "KEYS ON" nick named "T.L.B"

07-10-2010	#6
vettn71 Join Date: Oct 2008 Location: Colleyville, TX Posts: 272	Re: 90 ZR-1 running bad. 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

07-10-2010	#2
ZZZZZR1 Banned BANNED Join Date: Oct 2006 Location: MD Posts: 3,674	Re: 90 ZR-1 running bad. 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). 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 (very reasonably priced) Coil packs are on ebay and the injectors are bosch. Keep us updated David

07-10-2010	#7
zr1nsxgto Join Date: Apr 2007 Location: Greenwood Indiana Posts: 50	Re: 90 ZR-1 running bad. 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!

07-10-2010	#8
ZZZZZR1 Banned BANNED Join Date: Oct 2006 Location: MD Posts: 3,674	Re: 90 ZR-1 running bad. RC's are the best, but pricey.... Bosch seem to do the job and VERY reasonably priced.

07-11-2010	#9
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,609	Re: 90 ZR-1 running bad. Hello & welcome to our asylum! I would tend to agree with the fuel vapor lock theory.....fwiw 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. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member Last edited by tomtom72; 07-11-2010 at 08:09 AM. Reason: forgot this

07-11-2010	#10
zr1nsxgto Join Date: Apr 2007 Location: Greenwood Indiana Posts: 50	Re: 90 ZR-1 running bad. 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.

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