schmack73

I have a 91 corvette that I recently purchased. The previous owner said it would vapor lock at times.. Well, I took the vette out on the road trip and it died twice on the hwy. it was on cruise control and it just started slowing down then it was like starving for gas and died. I started it right back up and drove probably another 1 hr then it did it again, so I cranked it again and continued to drive home. It didn't die the remaining 3hrs on the road.

When I made it home, I put fuel injector cleaner in the gas tank. The next day I drove it to work and back no problem then about an hour later I tried to start it wouldn't start. I waited 2 hours later and it started right up. This same scenario happened again so I'm thinking what is up...I took to a mechanic and he replaced the fuel pump and ignition coil.. It has rough start up now.. You have to push on the gas to have a smooth start is what the mechanic told me that didn't sound right.. It didn't perform like that before so when I was driving back home the car starts to run sluggish and the code "SYS" is flashing by the digital speedometer. I've never seen this code before. It runs worse after the new fuel pump and ignition coil... The previous owner said he replaced the ECM & computer chip.. I don't know if this has anything to do with it.. I took it to a classic car shop here in town to see if they can fix the problem.. Has anyone ever heard or had this problem?? Any suggestions??

GKK

What are the Diagnostic codes?...

Get the codes from the ALDL port under the driver side knee panel.

The first mechanic should've done this first before replacing any parts.

AirForceOne!

Vapor lock usually happens on carbureted vehicles, not fuel injected ones. I would check your fuel pressure and your fuel injectors.

How many miles does she have on her?

Just a guess, but I'll bet the culpret is your fuel filter or the sock screen in your fuel tank!

Cliff Harris

...And C4 Corvettes can't vapor lock. It's not possible.

Pull the error codes:

http://forums.corvetteforum.com/1574918379-post18.html
http://corvettephotographs.com/c4vettes/codes.htm

What they mean:

http://forums.corvetteforum.com/1576116036-post35.html

In general, the early ECMs are pretty stupid and the error codes are very basic, but at least they can point you in the right direction.

mnstrlt1

Maybe it's something "simple" like a fuel filter! You didn't mention that this was replaced. I'd also check fuel pressure, might be the reglator or the problematic stock fuel injectors.

davewhtt

Leftoverture

Just a guess but it sounds like you have one or more bad fuel injectors.

tbirdsps

If I was a guessing man....and I am. I'll bet the fuel pressure is dropping off. 1. AirForce 1 and mnstrlt1 probably have it right or 2. The fuel pump is getting hot and losing the ability to maintain pressure.

Like the old saying. If you think it's ignition check the fuel system.

schmack73

She has 103k

schmack73

The mechanic did mention the the fuel pressure was at 40-50 and it should be higher. I have the vette at the classic shop in town. I'll give them a call and see if they found the problem or make suggestions of the ideas you guys have given me.

SunCr

Vapor lock was eliminated with Vapor Recovery or by sending fumes to the Charcoal Canister where they are held until conditions are right to suck them into the intake - that fattens the mix, but the O2 sees the enrichment and cuts back the pulse width on the Injectors to keep it happy. If your Vette has a vapor lock problem, your Shop should know how to check it out. More often than not, it's the Checkvalve on the left frame rail, in the engine compartment, and/or fuel soaked Canister. Your Fuel Pressure is fine. Shop could always scan it to see if it's Rich and then go through the Trouble Tree for a Rich Condition until the cause is found.

MrWillys

A bad injector can heat the injector driver in the ecm and be the cause of temporary failure. If the injectors are original they should be replaced.

schmack73

[QUOTE=schmack73;1584616367]I have a 91 corvette that I recently purchased. The previous owner said it would vapor lock at times.. Well, I took the vette out on the road trip and it died twice on the hwy. it was on cruise control and it just started slowing down then it was like starving for gas and died. I started it right back up and drove probably another 1 hr then it did it again, so I cranked it again and continued to drive home. It didn't die the remaining 3hrs on the road.

When I made it home, I put fuel injector cleaner in the gas tank. The next day I drove it to work and back no problem then about an hour later I tried to start it wouldn't start. I waited 2 hours later and it started right up. This same scenario happened again so I'm thinking what is up...I took to a mechanic and he replaced the fuel pump and ignition coil.. It has rough start up now.. You have to push on the gas to have a smooth start is what the mechanic told me that didn't sound right.. It didn't perform like that before so when I was driving back home the car starts to run sluggish and the code "SYS" is flashing by the digital speedometer. I've never seen this code before. It runs worse after the new fuel pump and ignition coil... The previous owner said he replaced the ECM & computer chip.. I don't know if this has anything to do with it.. I took it to a classic car shop here in town to see if they can fix the problem.. Has anyone ever heard or had this problem?? Any suggestions??

10-1-2013 Update, Well guys, the corvette is still at the shop going on 3 months. They told me the fuel flow & injectors are good, but the problem is probably a ground wire issue. The car runs fine one day then the next day it's crap. I'll give him to Thursday then I'll go pick it up. He seems like, he is stumped about the situation. I don't know what to do other than go to the "dealership" and see if they can fix it.. I hate dealing with our dealership..Any corvette specialist in the Odessa/Mindland tx area???

MrWillys

Have they ohm'd the injectors yet? My guess is one or more are bad, and overheat the injector driver in the ECM, so it is a short to ground?

zr1fred

Quite possibly the pickup coil in the distributer, could also be the ignition module. Your fuel pressure is okay, possibly on the high side.

Y-ME

Get a new mechanic, they run about 32 psi. No such thing as Vapor lock on a Fuel injected car.

solaris_vii

my 89 would do the same shenanigans, had one injector that was always bad and 2 more than were bad when warm. ohm check them cold and hot, super easy test and will tell you real quick if theyre good or bad. got a new delphi set from fic and car runs better than it ever had!

Brian308gts

I had the same symptoms with my 1992, and after replacing a whole bunch of parts it turned out to be the opti-spark all along.

After having it replaced my car has been perfect ever since.

UNCLEBILL

Its a 1991 so its still the L98 engine...no optispark. Do NOT put fuel injector cleaner in as you have multec injectors and that will kill the injectors...have a 1990 and did the same thing when I first got it and threw in the cleaner. Within weeks lost a couple injectors with the same symptoms you mentioned. Cold the injectors should read 16.5 ohms...+/- .5. Put a set of Bosch 3 injectors in from FIC (22# ones) and problem solved. Researched it and GM was putting notices out to dealers about not putting fuel injector cleaner in the 1990. Sounds like they had to do a lot of injector replacements.
Bill

eatmydst1234

His '91 doesn't have an optispark