Help! 92 LT1 running terrible.....experts needed!

[CT-C4-92]

Hi,
I am new to this forum, and am excited to see a ton of great info. I'm from Killingly, Connecticut and have a 92 vert and also a 67 Chevelle (10 sec drag car). Glad to be aboard!

I did a search regarding my problem, but could not find any concrete info to help! I apologize in advance as this is going to be a bit long!

Ok, so my 92 LT1 has been giving me problems for a while now. Here is the history. Car has around 58,000 miles on it. I had changed the opti, plugs, wires, coil, and H2O pump at around 35,000 miles. Drove home from work one night...50 miles...and it was running great. Shut it off for about 1/2 hour, got back in and the exhaust note had become horrible....yes just like that! The car ran, but felt very low on power. Burping and backfiring out of the exhaust. Shaking when accelerating. It sounded ok when idling.

So, I did some trail and error mechanics, after talking with some guys and getting some codes.....changed the TPS, driver's catalytic convertor, driver's O2. Still no luck. Changed the fuel filter, no dice.

The car still running horrible. Note: It would come "back to life" for small spurts and seem fine....only to revert to bad in a few minutes. The computer wasn't rally giving any useful codes at all. Did the fuel pressure tests, etc from the FSM and decided the pump wasn't a problem. Held pressure after turning key off

Had a mechanic I know take a look and scan it. (He's not a vette or LT1 expert). He determined that cylinders 2 and 4 weren't firing. He did a compression test and he said they were fine. He advised that it might be the opti.

So, this past weekend, I bit the expensive bullet and changed the opti, plugs, wires, and coil AGAIN! The car started up nice....and idled nice (prior to water pump install). Seemed smooth, so I was hopeful. Got it all back together and took her for a spin. TERRIBLE! It was lacking power again, sounded terrible, and shaking horribly. Got home and she was around 180-200 degrees. Let her idle. The car was literally rocking all over the place visibly. It seemed to be "surging or skipping", and I could smell oil...and some smoke was coming from behind the motor.

Anyway, Sorry for the long post, but I am desperate. Any insight will be much appreciated!

ADDNG FURTHER DETAIL TO THE ORIGINAL POST......

Code pulled PRIOR to new opti, plugs, wires, an coil....

43 knock sensor circuit

45 Bank 1 (left front) heated oxygen sensor #1 circuit (rich exhaust indicated)

63 Bank 2 (Rt front) heated oxygen sensor #1 circuit (open circuit)

64 Bank 2 (Rt Front) heated oxygen sensor #1 circuit lean exhaust indicated)

CODE 15 pulled TODAY....after the new opti,etc...

MORE INFO....

Also....I started it, and it sounded healthy. It got progressively worse as it heated up. I pulled the injector wires off one by one. The driver's side changed the idle when pulled. The passenger made no difference when pulled. I also touched a screwdriver the each injector while it was running and I could feel pulsing in ALL of them.

Lastly, I used propane to check for vacuum leaks. Found none.



Thanks,
-Rick

 

[Hib Halverson]

Is the MIL on and if so, what codes are set? We need to know that regardless if the codes set are deemed useful or not.

Also, you said you ran the fuel pressure tests in the FSM but decided the fuel pump was not a problem, but more info is needed. Was the fuel pressure in the range listed in the FSM and did it hold once you turned the key off?

Did a scan test indicate both oxygen sensors were working properly?

Have you inspected the injector wiring harness and connections?

Have you inspected the connections at the ECM?

 

[CT-C4-92]

Is the MIL on and if so, what codes are set? We need to know that regardless if the codes set are deemed useful or not.

Also, you said you ran the fuel pressure tests in the FSM but decided the fuel pump was not a problem, but more info is needed. Was the fuel pressure in the range listed in the FSM and did it hold once you turned the key off?

Did a scan test indicate both oxygen sensors were working properly?

Have you inspected the injector wiring harness and connections?

Have you inspected the connections at the ECM?

Yes, it held pressure as outlined in the FSM. Hmmm..inspect injector harness, what would I look for?

I will take a look around the ECM.

Here are the codes it gave at that time. The service engine light did not come on the other day after installing new opti...etc.

43 knock sensor circuit

45 Bank 1 (left front) heated oxygen sensor #1 circuit (rich exhaust indicated)

63 Bank 2 (Rt front) heated oxygen sensor #1 circuit (open circuit)

64 Bank 2 (Rt Front) heated oxygen sensor #1 circuit lean exhaust indicated)


thank you.

 

[CT-C4-92]

I took a read of the codes tonight......the only code coming up is a Code 15....which has to do the CTS. Not sure if that has anything to do with the problems....

 

[tmkassin]

Do you have a K&N air filter? The oil from it coats the MAF and causes all kinds of problems. All you have to do to fix it is buy a can of MAF cleaner and spray it. If that doesn't help then do an OHMs check on your injectors. If I remember right they should check about 12 ohms. If you have any bad ones it is best to replace them all. I put Bosch injectors in my 92 and they made a huge difference in performance. You can find the guy that sells them on the search option here on CAC. Hope this helps.

 

[CT-C4-92]

Do you have a K&N air filter? The oil from it coats the MAF and causes all kinds of problems. All you have to do to fix it is buy a can of MAF cleaner and spray it. If that doesn't help then do an OHMs check on your injectors. If I remember right they should check about 12 ohms. If you have any bad ones it is best to replace them all. I put Bosch injectors in my 92 and they made a huge difference in performance. You can find the guy that sells them on the search option here on CAC. Hope this helps.

Yes, I have a K&N filter on it. Although it has been on there for about 10+ years.....and embarrassingly I have never taken it out to clean and re-oil it. I will take a look at the injectors. I assume the procedure for testing the OhMs is in the FSM somewhere. Hopefully, I can find it.....I suck at the FSM!

Thanks for the input.

 

[CT-C4-92]

Check the fuel injector OhMs tonight. Is this procedure in the FSM?

1 - 12
2 - NO reading at all?
3 - 4
4 - 12
5 - 12
6 - 12
7 - 4
8 - 12

So, does this mean I have 3 bad injectors?

Also....I started it, and it sounded healthy. It got progressively worse as it heated up. I pulled the injector wires off one by one. The driver's side changed the idle when pulled. The passenger made no difference when pulled. I also touched a screwdriver the each injector while it was running and I could feel pulsing in ALL of them.

Lastly, I used propane to check for vacuum leaks. Found none.