No exhaust leak....and the noise is ther even with open headers!!????

 

Have you checked your timing? What does it read at idle? When yiou rev the motor does the timong fluctuate? If noy, you have a disconected EST wire which is only disconnected to set the base 6 degrees of initial timing for the computer. If you truly have a miss coming out of only one cylinder, it has to be one or more of the following:

Bad plug
bad injector
bent valve (hope not)
valve out of adjusment
broken valve spring
bad wire going to your injector
bad dist cap/rotor
bad spark plug wire
cracked/stuck piston ring
blown head gasket (on the out portion of the head).

Good luck!

 

Joe,
I bought an 89 L98 to put in my 57 Chevy truck, and when I took the heads apart, I noticed that all of the exhaust valves were pitted somewhat. Two were more than the rest, and it seemed that the one that was the worst was number 8.
I mentally corresponded that number to where the egr valve was placed from the factory.
The engine had 97,000 miles when pulled.
If you have the stock intake manifold, I would check it for cracks, and do a compression check cold and hot.
Do the cold compression check just after starting it up and get it slightly warm, and the hot after the thermostat opens and you get at least 180 degrees.
Remember, the 89-91 cars use the computer programming to eliminate the cold start injector, and call for more fuel based on the temp sensor in the front of the manifold under your air filter.
If you have a marginal injector, cycling it longer and more frequently in open loop may mask a failing injector in the closed loop mode.

 

Did cold and warm compression tests///about 70 PSI per cylinder.
Don't know how to "Ohm the Injectors."

 

You should have more than 70lbs per cylinder.. My high compression 383has anywhere from about 190-210 during cranking.. If your engine is stock I'm thinking you should be in the 150-170 range.

 

To ohm the injectors simply take a multimeter and switch the positive lead to the hole with the "Ohm" (horseshoe) and leave the black lead in the common hole. Switch the multimeter to the Ohm sign (the button that has less than 100 ohms). You don't have to remove the injectors, just carefully pull the injector plug-ins off one at a time and take the red and black leads of the multimeter to the two pins in each actual injector (it doesn't matter which lead goes to which injector connector). This will not tell you if the injector is leaking, but it will determine if the injectors all have operable solenoids. Mine Ohm'd out somewhere in the 14-15 Ohm range.

 

" You should have more than 70lbs per cylinder.. My high compression 383has anywhere from about 190-210 during cranking.. If your engine is stock I'm thinking you should be in the 150-170 range. "

I only tested with 3 revolutions...I probably could have gotten more if I went 4.



" To ohm the injectors simply take a multimeter and switch the positive lead to the hole with the "Ohm" (horseshoe) and leave the black lead in the common hole. Switch the multimeter to the Ohm sign (the button that has less than 100 ohms). You don't have to remove the injectors, just carefully pull the injector plug-ins off one at a time and take the red and black leads of the multimeter to the two pins in each actual injector (it doesn't matter which lead goes to which injector connector). This will not tell you if the injector is leaking, but it will determine if the injectors all have operable solenoids. Mine Ohm'd out somewhere in the 14-15 Ohm range. "

Not knowing, I tested them on the 400 Ohm scale and 3 out of 4 had 17.9 ohms and the #5 injector (which is the area I thought the problem existed in) only read 7.3 ohms.
That might explain why there was no noticeable difference when I pulled that plug wire off, even though there was spark coming through it.
I hope I've located my problem. I'll send them out to Cruzperformance ASAP.

I'll post my results in a week or so.
Thanks

 

I think you've found your problem.... That injector is dead...

 

OK, now where do I get injectors from. Rich Jensen at Cruz Performance says he will not restore the Multec type injectors and I should get new ones. I only want stock , size etc.
Suggestions??

 

Joe: Here is a good thread on replacement injectors for the crappy Multec injectors:

http://forums.corvetteforum.com/show...post1560357682

I have heard positive comments on the new Accel injectors and the rebuilt injectors from Howard Haack. Racetronics, a supporting vendors also has some replacement injectors at a good price.