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Help! 1991 L98 Chattering/Stalling out

stratinik

Member
Joined
Jul 14, 2009
Messages
12
Location
06905
Corvette
1991 red L98
· Purchased a 1991 Chevy Corvette L98 April of 09 with approximately 21,300 original miles, six speed transmission. Car mostly sat in the garage as the previous owner also lived in Florida for half of the year.
· Previous owner stated that he replaced the fuel injection, but could not provide details as for why, if anything else was done or repair receipts. Injectors do look replaced.
· Registered the auto and passed CT emissions inspection beginning of June 2009.
· Oil level when checked from dipstick was ok, when viewed from opening in valve cover there didn’t appear to be much there.
· Took to Valvoline and had oil flushed, replaced, and also had transmission fluid changed. Agent stated that the oil pump gasket should be replaced next oil change, looked like it had blue glue on it.
· Replaced air filter with one from NAPA..
· Auto does not appear to be leaking any fluids in engine compartment, and I cant smell anything abnormal like burning. No smoke from exhaust.
· Car shifts and drives well, no seeming issues with clutch, no over heating, steering, and all interior electrical features seem to work as they should.
· Car most likely has not been tuned up at all in the last 18 years, plugs and wires look original, checked visually and cannot detect any burnt or cracked wires.
· For the first two weeks of ownership, car starts with no hesitation, and when cold makes no noises at all while driving for the first approximately 15 minutes. No error codes appear.
· After auto warms up, about 15 minutes, car begins to make an off rhythmic chattering sound. Hard to detect from where, sounded like could be near transmission or noisy lifter.
· At highway speed, car showed “SES” light as solid but seemed to run fine, noise would get more chattery but only when car was at idle. When auto turned off and restarted, “SES” light would be gone.
· Car would make the chattering noise when clutch was depressed in or out. No difference.
· Had a mechanic friend check error codes with diagnostic tool and car had history of code “32” for EGR valve. Friend replaced EGR valve early/mid June
· Car continued to exhibit same condition after change of EGR valve. After warm up, noise now progressed from chattering to sound like a noisy lifter ticking, rhythmic from passenger side near firewall.
· I added fuel injector cleaner and noisy lifter lubricant to gas and oil.
· I have run 2 to 3 full tanks of gas through auto since purchased. High octane.
· Upon startup, engine runs mildly rough with very slight hesitation at idle to throttle response.
· On gauges, during driving conditions, engine temperature, oil pressure, battery voltage are all within normal ranges. Oil temperature does not appear to go above 140-150, low side of gauge for 10-15 minutes.
· Recently drove car to work from Stamford to Rye NY (about 22 miles) car ran fine at highway speeds with no error codes. On return trip home from work on the highway, car suddenly began to sputter and seem to lose power and then regain it repeatedly, but was still running. I shifter into lower gear and got off the highway. Car ran for a few miles, then stalled. Restarted, would go a couple of miles and stall again exhibiting the same sputtering problem. “ SES” light appeared as solid. Car got to a point that it would not restart. Would crank strongly but not turn over. Had it towed home in Stamford.
· Next day after tow, car started up immediately, with no “ SES” code on the dash.
· Had mechanic friend check fuel injection pressure, and appeared fine, also checked for codes with diagnostic tool and none where stored or retrieved.
· Week of July 14th, started auto right up, let warm up for 10 minutes and then drove around the neighborhood for 10-15 minutes. Car then began non rhythmic chattering sound but no sputtering, so I returned to the house, chattering begin to shift more to the rhythmic noisy lifter type sound. Let car idle in driveway for 5 minutes, and it stalled out by itself and would not restart when attempted. Cranked but no turn over. (PLEASE HELP WITH ANY IDEAS?)
 
You might want to post this in the C4 forum and you will probably get more responses.

That being said, my '89 had the infamous rough idling problem and did exactly as you described. Ran OK at start up. As the car warmed, idle got more and more rough, finally died. Cranked, but would not start. In my case, the injectors were bad. If I remember right, they should be around 16 ohms (I could have forgotten since then, but I think that's right). Anyway, an ohms check of my injectors showed them WAY below specs - some 10, some 11, one was at 6. I replaced the injectors and all was well. This seems to be a very common cause of the syndrome you described. Get the injectors ohms checked so you can fix the issue or rule it out as the problem.
 
Stratinik, I'm going to move this to the C4 Technical and Performance Forum. :)
 
When it is warm have the exhaust backpressure checked at the O2 sensor port.
You may have plugged catalytic converter . Although usually you would experience increased engine temp.

Glenn
:w
 
Does it lope idle when warm?
 

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