'91 missing and would like a second opinnion - Page 4 - ZR-1 Net Registry Forums

Demps · 02-28-2010

Any chance for bad gas? Running Shell nitrogen gas successively?

ZR-1Mikko · 02-28-2010

ok I will try to list here what I have done so far:

Injectors -2years old Acccels with about 10k miles on them. I ohmed them out and they all had matching readings both hot and cold.

Coils - brand new MSD. I ohmed them out and they all had matching readings when cold. I did not ohm them out hot since they are new.

wires - 2years old MSD with 10k miles on them. I ohmed them out and they all had matching readings when cold.

Plugs - brand new Ac delco 41-602. The old ones that I took out after this issue came up were all the same color and condition, so it seems that it is not any specific cylinder having the problem...

O2 sensors - Changed out new one on one side and replaced the other side with the one that came off the side with the new one. Did this after I tested that the new one did not fix the issue.

Fuel pumps - Brand new Airtex with new strainers (these are the ones sold as replacement for LT-1)

Fuel filter - brand new and also drained some gas out of the tank to make sure there is no dirt left.

Fuel pressure - about 45lbs when engine running. With key on and engine off the pressure is leaking a little bit, which Ken thought that might be a leaking injector.

Secondaries - We were able to see the actuator arms moving when stepping on the gas

ECM - tried one off Ken's 1990 and it did not fix the problem

And then the current syptoms:
When cold the car iddles fine right after start, but starts to randomly miss about 2 minutes after start. (It might have the miss right off the start, but I can't really hear it since the air pump is running)
When taking off cold the car studders the same was as it does when hot. I can feel the studder on all rpm's hot and cold. The only time I don't feel it is when I'm moving at steady speed with a steady throthle around 1500-2000rpm.
And just to be clear the car does not pull the way it is supposed to...

So at this point I'm out of tricks, energy and ideas :

Dynomite · 02-28-2010

Quote:

Originally Posted by Jeffvette

Mikko, if you are having a rapid fuel pressure loss, you have an injector that is bad, or one that is possibly grounded open and draining the fuel.

You can pull the plenum and dislodge the fuel rails. Lay some shop rags or heavy duty paper towels underneath the injector tips and then prime them, and see what is leaking.

But definitely check your injector wire harness to see if you have crushed one of the wires.

Did you try Jeffvette suggestion above

I had almost zero compression on one cylinder with one secondary injector having very low resistance and did not have as severe symptoms as you are having

This is very interesting

Demps · 02-28-2010

Personally not a fan of non-GM coils. Others have fought that--guy on this board from OK.

What is the plug gap?

Are you sure the ignition module connector is tight?

Wish I were there to help. Should be there in 3 weeks if it is still acting up.
Car will go closed loop about your trouble time. My O2 symptom was passing 126F water temp it stumbled then would correct itself.

ZR-1Mikko · 03-01-2010

It really can't be the wire harness, since the problem came up overnight without touching anything in the car.

Now if it was just one injector bad wouldn't I be able to see that on the plug?

I will check all the connectors one more time tomorrow....

Zr1 Destroyer · 03-03-2010

DIS mod......

ZR-1Mikko · 03-03-2010

I have not checked the dis mod yet...

Did check all the connections the other day and no success...

ZR-1Mikko · 03-04-2010

before I pull the plenum one more time I have couple things I'm wondering if anyone would happen to have answers for?

So if I pull the injectors to check for leaks can I just connect the battery and turn the power on from the key to prime them or what would be another way to prime them?

Is it possible to ohm out the Dis module to see if it is failing? Or should I just borrow someones Dis and swap it?

Demps · 03-05-2010

Quote:

Originally Posted by ZR-1Mikko

before I pull the plenum one more time I have couple things I'm wondering if anyone would happen to have answers for?

So if I pull the injectors to check for leaks can I just connect the battery and turn the power on from the key to prime them or what would be another way to prime them?

Is it possible to ohm out the Dis module to see if it is failing? Or should I just borrow someones Dis and swap it?

Small tab connector on wire bundle going into ECM is fuel pump test--jumping to + on battery will run fuel pump and pressurize rail.

DIS is not testable without a specialty test set (I would imagine).

ZR-1Mikko · 03-05-2010

Thanks for the tips!

02-28-2010	#31
Demps Join Date: Jan 2006 Location: Niceville Posts: 997	Re: '91 missing and would like a second opinnion Any chance for bad gas? Running Shell nitrogen gas successively?

02-28-2010	#32
ZR-1Mikko Join Date: Dec 2005 Location: Las Vegas Posts: 108	Re: '91 missing and would like a second opinnion ok I will try to list here what I have done so far: Injectors -2years old Acccels with about 10k miles on them. I ohmed them out and they all had matching readings both hot and cold. Coils - brand new MSD. I ohmed them out and they all had matching readings when cold. I did not ohm them out hot since they are new. wires - 2years old MSD with 10k miles on them. I ohmed them out and they all had matching readings when cold. Plugs - brand new Ac delco 41-602. The old ones that I took out after this issue came up were all the same color and condition, so it seems that it is not any specific cylinder having the problem... O2 sensors - Changed out new one on one side and replaced the other side with the one that came off the side with the new one. Did this after I tested that the new one did not fix the issue. Fuel pumps - Brand new Airtex with new strainers (these are the ones sold as replacement for LT-1) Fuel filter - brand new and also drained some gas out of the tank to make sure there is no dirt left. Fuel pressure - about 45lbs when engine running. With key on and engine off the pressure is leaking a little bit, which Ken thought that might be a leaking injector. Secondaries - We were able to see the actuator arms moving when stepping on the gas ECM - tried one off Ken's 1990 and it did not fix the problem And then the current syptoms: When cold the car iddles fine right after start, but starts to randomly miss about 2 minutes after start. (It might have the miss right off the start, but I can't really hear it since the air pump is running) When taking off cold the car studders the same was as it does when hot. I can feel the studder on all rpm's hot and cold. The only time I don't feel it is when I'm moving at steady speed with a steady throthle around 1500-2000rpm. And just to be clear the car does not pull the way it is supposed to... So at this point I'm out of tricks, energy and ideas : __________________ If you don't put the miles on it, someone else will... Last edited by ZR-1Mikko; 02-28-2010 at 09:42 PM.

02-28-2010	#34
Demps Join Date: Jan 2006 Location: Niceville Posts: 997	Re: '91 missing and would like a second opinnion Personally not a fan of non-GM coils. Others have fought that--guy on this board from OK. What is the plug gap? Are you sure the ignition module connector is tight? Wish I were there to help. Should be there in 3 weeks if it is still acting up. Car will go closed loop about your trouble time. My O2 symptom was passing 126F water temp it stumbled then would correct itself.

03-01-2010	#35
ZR-1Mikko Join Date: Dec 2005 Location: Las Vegas Posts: 108	Re: '91 missing and would like a second opinnion It really can't be the wire harness, since the problem came up overnight without touching anything in the car. Now if it was just one injector bad wouldn't I be able to see that on the plug? I will check all the connectors one more time tomorrow.... __________________ If you don't put the miles on it, someone else will...

03-03-2010	#36
Zr1 Destroyer Join Date: Oct 2005 Location: Candy Apple...yUmMy Posts: 1,137	Re: '91 missing and would like a second opinnion DIS mod......

03-04-2010	#38
ZR-1Mikko Join Date: Dec 2005 Location: Las Vegas Posts: 108	Re: '91 missing and would like a second opinnion before I pull the plenum one more time I have couple things I'm wondering if anyone would happen to have answers for? So if I pull the injectors to check for leaks can I just connect the battery and turn the power on from the key to prime them or what would be another way to prime them? Is it possible to ohm out the Dis module to see if it is failing? Or should I just borrow someones Dis and swap it? __________________ If you don't put the miles on it, someone else will...

03-05-2010	#40
ZR-1Mikko Join Date: Dec 2005 Location: Las Vegas Posts: 108	Re: '91 missing and would like a second opinnion Thanks for the tips! __________________ If you don't put the miles on it, someone else will...