91 ZR-1 Cutting Out Under Load

[tomtom72]

Greg,

With out being forward I will say this. If you think about what's happening it is unlikely it is the EPROM or / and the ECM. In retrospect I fell for the same thing, ECM, so now I have a spare! Reason I say unlikely is that the few things the ECM controls but has no direct feed back control loop from are the injectors, hence no codes. The only feed back to the ECM from the injectors are the O2 sensors but they can only code if they fail. If the motor is rich or lean the only way the ECM knows is if it can read the O2 data. If the O2 data shows up on a scan and presents in a manner consistant with the expected then one must think that the O2's and the ECM are good. Therefore, the only other parts that can be questionable in the fuel system having to do directly with combustion are the injectors. Assuming the rest of the ignition system is up to snuff and the fuel pumps & regulator & F/F are okay. At least that is my simplistic understanding of the EEC system as it relates to this case.

Oh and as far as the cleaning & flow testing, I learned from the netregistry site that any efforts in that direction are mostly meet with less than satisfactory results, not worth doing seems to be the general concensus on that subject. That and the fact that before 92 the coils are not alky proof.

I have a spare ECM, and I can remove the 90 EPROM and lend it to you if you feel you want to try that as a diagnostic aid. Like I said, I fell for that 'easy out' because a mechanic said "oh those ECMs su#k, they always fail!" Soooo, now I have a spare! I believe it is for a 91 as the 90 ECMs are NLA.


Tom

[GregCrowe]

Originally Posted by Z Factor

I hear your frustration and know you do not want to bite the bullet and go the injector route, but sorry to say that is most likely your problem.

As to not selling I can give you several reasons but here are two very good ones . First is that when your baby is running right you have a great time that cannot be matched by other cars, especially in a moderate price range (assumption on $$ ). The second reason is that if you were to try and sell it with the existing problem, you are not going to get as much for it as you would if it were in tip top shape. The bottom line is that you bought it for a reason and just need to get it running right to recapture the great feeling of owning a KOTH

I hear what you're saying. However, I do have a Lingenfelter 383 Corvette and an LS-1 WS6 Trans Am that will both run circles around the ZR-1 so it's not like I'm blown away by it when it is running right.

As to the injectors, is there a reasone to change all 16 or should I just change the 8 primarys?

[tccrab]

Originally Posted by GregCrowe

As to the injectors, is there a reasone to change all 16 or should I just change the 8 primarys?

Greg:

I've was just at this particular crossroad just a couple of weeks ago and in the end I decided to replace all 16.
My decision was based on how many times I wanted to pull the plenum to work on fuel injectors.
Once was enough.
I went with the Accels, would have went with the RC's but didn't want to empty the savings account and the grandkids college fund.

I too had a misfire that, after all was said and done, was repaired by replacing all the fuel injectors AND the ECM. I had three primary injectors go bad and somehow they took out the associated injector drivers in the ECM with them.

Good luck!

TomC
'90ZR1 #792

[Z Factor]

Originally Posted by GregCrowe

As to the injectors, is there a reasone to change all 16 or should I just change the 8 primarys?

If you are already fed up with pulling the plenum then I'd say replacing all 16 is the way to go despite the added cost. If however you want to save money or don't mind another possible plenum pull then only replace the one/s you find that are faulty. I say this from experience since I had one leaking injector a couple of years ago and only replaced it. I have not had any others fail, so I am happy with my decision. If however another one went out within a few months then I would feel the opposite.

As to the cleaning, many (not all) have had problems not to long after spending the money and eventually had to replace them anyway.

So try to keep your chin up and hopefully you will get everything squared away soon.

[GregCrowe]

Originally Posted by Z Factor

If you are already fed up with pulling the plenum then I'd say replacing all 16 is the way to go despite the added cost. If however you want to save money or don't mind another possible plenum pull then only replace the one/s you find that are faulty. I say this from experience since I had one leaking injector a couple of years ago and only replaced it. I have not had any others fail, so I am happy with my decision. If however another one went out within a few months then I would feel the opposite.

As to the cleaning, many (not all) have had problems not to long after spending the money and eventually had to replace them anyway.

So try to keep your chin up and hopefully you will get everything squared away soon.

Well, I do know my problem is on the primary side. Is there a way to isolate it to one specific injector? Being a pre-OBD2 car, can a Tech 2 scantool find the problem on a specific cylinder?

[Tom]

I didn't see any mention of you measuring the injector resistances. It is very easy to do and would quickly tell you if you have injector coils going bad, you don't have to pull the plenum to check them. Here is the link to an article on Marc Haibeck's website about measuring the injector resistance: http://www.zr1specialist.com/HAT%20W...Resistance.htm

The diagram on his site is for a '91 though it would be much easier to read in the shop manual if you have one.

[GregCrowe]

Thank you Tom, that looks exactly like what I need to test, specifically where they mention "Solenoid coils are more likely to exhibit shorts when they are hot".

Let me see if I understand what they are saying to do to check primary injectors. Let me know if this is right:

1. Run car long enough to get hot and heat soaked
2. Remove power to ECM
3. Pull Injector 1 fuse from fuse panel on passenger end of dash
4. Test resistance between the right side(closet to nose of the car) of the fuse plug-in ........... and the 8 injector connections on the ECM connector A(A8,A3,A2,A7,A1,A12,A13,A18)

Looks like I'll need to extend the wires on my volt-meter to reach that far.

[1990 quasar blue]

Originally Posted by GregCrowe

I hear what you're saying. However, I do have a Lingenfelter 383 Corvette and an LS-1 WS6 Trans Am that will both run circles around the ZR-1 so it's not like I'm blown away by it when it is running right.

As to the injectors, is there a reasone to change all 16 or should I just change the 8 primarys?

http://www.zr1specialist.com/HAT%20W...%20testing.htm If you want them tested individually.

If you want to change just 1,2, or 8 go ahead but, you'll be changing the rest sooner or later. I would change them all. Either RC's for 1100.00 or Accells for 500.00. As far as the 383 and the WS6 you're comparing two heavily modded cars to one that's stock and 15 years old. Make that 91 a 415 then reassess.

[GregCrowe]

Originally Posted by 1990 quasar blue

http://www.zr1specialist.com/HAT%20W...%20testing.htm If you want them tested individually.

If you want to change just 1,2, or 8 go ahead but, you'll be changing the rest sooner or later. I would change them all. Either RC's for 1100.00 or Accells for 500.00. As far as the 383 and the WS6 you're comparing two heavily modded cars to one that's stock and 15 years old. Make that 91 a 415 then reassess.

Please excuse my ignorance but what does "RC" stand for? How about using the 93-95 Multec's referred to on the linked page? Also, I see the Accel part number listed in another thread as 050121(050821 for an 8-pack) and are the secondary injectors the same as the primaries?

RC is Russ Collins

www.rceng.com