Fuel Problem Or What?

[billroth]

I have a 88 with 71k and here is whats been happening. After driving it for awhile I step on the gas it stalls and I hear a couple of muffled backfires. I let up on the gas and it remains running. Hit the gas hard, transmission down shifts and nothing. Once I got it at highway speeds and it was fine for 80 miles.

To date I have had the Vette at a Chevy dealer for about 2 weeks and $1000+ later, I still have the problem. They have replaced the Mass Air Flow Sensor, computer, fuel filter, EGR valve, fuel pump pressure is good, Cat. converter is okay and replaced several electrical connectors. They get several different codes, but I never get a "service light".

Currently they get no code, but they observed that at a certain temp range about 165 to 170 degrees (approx) the stalling event starts up. If the car is driven at highway speeds during that temperture range its not noticed. When a fuel pressure gauge is connected, it shows it is starving for fuel during that temp range. We are going nuts :W trying to find a relationship now between the engine temp and the fuel pressure.

Any ideas?

 

[WhalePirot]

I wonder if there is a problem wih the fuel pressure regulator. When vacuum drops, as under hard acceleration, the regulator moves an internal vacuum diaphragm to increase fuel pressure. If it is sticking at a lower vacuum setting or leaking vacuum, the car will go lean.

I would think you could diagnose the function with a hand vacuum pump and a fuel pressure gauge..

It is too bad they didn't do a more thorough diagnosis before throwing parts and your cash at the problem.

May your trials end soon.

 

[redc4corvette]

If it was me and changing the EGR I would have thrown a regulator in he was right there.

 

[Achilles]

Sounds similar to a problem I just recently had with mine. It ran fine when it was cold, but would start cutting out and stall once warmed up untill it finally gave up altogether. It turned out to be the ignition module in the distributor. They are very heat sensitive. Good luck.

 

[Achilles]

BTW, it's hard to diagnose when it's working and there aren't any codes. But it is a pretty cheap & easy fix for a DIY, rather than paying Mr. Goodwrench $$$$.

 

[Hib Halverson]

First, what were the several different codes the techs got when you took the car in.

Secondly, when the engine is "starving" for when the coolant temp is 160 to 170, what are the pressure readings and how do they act (ie: low and consistent or low and fluctuating?).

Third, I'm a little unclear about then this driveability problem occurs. Is it only when the engine is between 165 and 170 OR does it start at between 165 and 170 then continue when the engine is that temperature or warmer.

Fourth, if you have a scan tester, have you noted that the engine goes from open to closed loop at that temperature?

Fifth, is the engine modified? If so, what are the mods?

Lastly, be careful about continued work by that dealer. They're just throwing parts at the problem and not doing a very good job of diagnosing.