Welcome to the Corvette Forums at the Corvette Action Center!

Help! 1991 L98 6 speed -Sputters/stalls -Please Help

stratinik

Member
Joined
Jul 14, 2009
Messages
12
Location
06905
Corvette
1991 red L98
Please Help -
· 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.
 
Have you looked under the distributer cap? Check under there for corrosion and such, that could lead to the sputtering and stalling out. I was having some issues with sputtering and stalling on a sbc (not a vette), but it turned out to be the distributer/pickup coil. Replaced the distribuer and it runs like a champ now.
 
same problem on 1991 Vette

I'm having the same problem currently. Thought it might be a fuel issue. Replaced fuel filter, checked for fuel pressure from fuel pump, seems OK. Mechanic seems stumped, leaning towards the ECM. Would appreciate any help or clues.
 
Have you looked under the distributer cap? Check under there for corrosion and such, that could lead to the sputtering and stalling out. I was having some issues with sputtering and stalling on a sbc (not a vette), but it turned out to be the distributer/pickup coil. Replaced the distribuer and it runs like a champ now.


2 tools I would recommend 1 is a Noid Light to test injector pulse, and a old spark plug well to test for spark, wedging between heat-shield and exhaust. so you can confirm the two most important things needed to run,since you already say the fuel pressure was good. you also may want to get a fuel sample from the injector rail or tank and look for pockets of water in the gas.
 
Last edited:
I also have a 1991 6 speed. That had the chatter. The problem was the dual mass flywheel. This particular fly wheel is a dual flywheel that absorbs all the vibration in the clutch area and makes for smooth shifting. The large rubber device between the two flywheels is bad , probably separating. Once a changed the flywheel and clutch the noise went away. This flywheel is not cheap so be prepared. But it did solve issue.. Good Luck..

Sent from my XT1080 using Tapatalk
 
Also GM does not recommend putting fuel injection cleanernin these cars because the type of fuel injectors in these cars are the disc type injector and the fuel flows over the coil portion of the internal parts of the injector to cool it down. When you put the injector cleaner in it eats away at the coil wire insulator inside the injector and eventually shorts out the injector and then the car stops running.. If this happens simply replace all injectors. I had the same problem . the car will not run with 1 bad injector because the computer goes into a protection mode so you don't fry it . so replace all injectors and fuel pressure regulator when all apart and once done the car will be like new. Mine runs great now. These two problems are common C4/issues .


Sent from my XT1080 using Tapatalk
 
As philbillyvette mentioned, the pickup coil in the distributor can go bad and exhibit what is called a "thermal condition."

When this happens the coil looses continuity as it gets hot as the engine runs and heats up. The layers of the coil expand and separate, thus loosing continuity and it ceases to send impulses to fire the coil. I'd also put a new module in while you are in there or just get a rebuilt distributor.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Advertise with the Corvette Action Center!

Double Your Chances!

Our Partners

Back
Top Bottom