sibilith

I bought my 1990 Corvette in August for $6000 with 78000 miles on it, in great condition without needing more than an oil change and a replacement fog light. The previous owner replaced the convertible top, the alternator, and the shocks, and regularly maintained it only driving it a couple times a month. I put some heavy mileage on it driving from FL to NC and back, as well as using it two or three times a week to drive across town for classes. I've since had to replace the brake booster but no other repairs.

The other day I drove downtown for a festival for about three hours, then came back and found that the car wouldn't start. The engine would start revving, and when you feathered the gas pedal while turning the key it would start, but as soon as you took your foot off the gas the car would die. The only difference in parking from any other time I've driven it was that it was parked on a downward incline, but I don't think it would make much difference. It's not an easy issue like the battery or the ignition, it would appear.

I had it towed to a Chevrolet dealership's service center, and they worked on it for 5 hours, going through all the systems that may prevent the car from starting. They scanned the ECM module, and no codes were triggered. The ignition system is good, the fuel injectors are good, and it's got a good spark. They are "up in arms" over the issue and say that the next logical step is to replace the Internal Air Control and run an induction service on the car to clean out the parts. This would cost $800 and wouldn't guarantee a fix, and I could pick it up now with only $70 + taxes for a car that doesn't run.

I'm not sure what to do and was wondering if any of you Corvette enthusiasts had any suggestions. I'm considering cutting my losses with the car and selling it to someone who has the time and resources to work on it. It's my only car, and even if I sink $800 into now and it runs, it might be $2000 next week. What are your opinions?

bogus

This sounds like some part dying...

1. Fuel Pressure? does it crash?
2. Spark?

My idea is one of the following:

1. Fuel pump
2. Fuel filter
3. Ignition module inside distributor

Them's there a goodly start!

WW7

If it starts , sputters , then dies , I would say fuel is the problem not spark, but both should be checked..I have never seen a ICM die like this, but that doesn't mean it couldn't happen so it may be wise to check that also......Did they check fuel pressure at the rails? I agree with Bogus on the fuel filter and fuel pump, you would be surprised how many dirty fuel filters have caused starting and running problems...You need to hook up a fuel pressure gauge and watch it while attempting to start the car , watch what it does when the car runs and then stalls. You should have somewhere around 40 to 42 lbs pressure at the schrader valve on the fuel rails with the key on.....Let me just add that if the dealership worked on the car for 5 hours including hooking up to there computer , you should owe way more then $70.00....WW

ToniJ1960

Not to mention if thy suggest $800 for some service and didnt check the fuel pressure even, get your car far away from them.

Kevova

If car didn't start incline but started on level surface fuel gauge maybe off or something related pick up in fuel tank. Idle Air Control and induction service shouldn't cost 800.00 I would take it to another shop or home and DIY. IAC can cause it not to idle, you wouldn't have to feather gas, you would have to hold pedal down a little to idle. Feathering gas tends to relate to a lack of fuel.

sibilith

Thanks for the input, guys. Given my car is around the 80000 mile mark, the IAC valve seems to be suspect. I've ordered a replacement and hope to work on it this Saturday. These guys at the chevy dealership don't seem to really know what they're doing, and I'm going to get the car back to my place for the time being. If it's not the IAC valve I'll check the fuel filter. I really appreciate the suggestions!

playsdixie

Sounds like fuel to me....a pressure guage on the rall will probable tell you...

Silver96ce

If you don't already have it - get an FSM, Factory Service Manual. It will have diagnostic charts for your year which will be invaluable to you. Most dealerships have gotten rid of all the manuals and diagnostic equipment used for C4 repair and maintenance. And probably most of the mechanics that worked on them have retired.

In the meantime, I would look at fuel pressure, the IAC, the IAC passages and TPS. Good luck.

XLR8 C4

I agree with checking fuel pressure at the rail. I had the same issue with my 1993 C4 and it was a 5 dollar fix. Open the hood and find the inlet fuel line going to the fuel rail. Should be over the number 8 cylinder. On your car there should be a small round disc in the fuel line going into the fuel rail. It is a shock absorber for the fuel injectors which has a rubber diaphragm inside it. The rubber diaphragm became dislodged and a times actually plugged the fuel line not allowing fuel to reach the fuel rail. The fix? Remove that small disc and attach the fuel lines with a piece of rubber fuel hose and use good clamps. 2000 miles later no issues. The way this was discovered? A fuel pressure gauge showed zero fuel pressure when it wouldn't start but perfect fuel pressure when it started. Also turn on the ignition to run only and with your hands feel if the fuel line is charged before that small disc and feel the fuel line after the disc and if it's plugged you shouldn't feel and pressure after it. Hope this helps or makes sense.

VikingTrad3r

Thanks for sharing this xlr8, this kind of thing could cause a heap of anguish undetectable by codes. VikingTrad3r

Tom400CFI

Its not the IAC. The IAC may cause it to stall w/o throttle input, but wouldn't require gas pedal "feathering" to run; with any throttle application, it would start right up and run.

I 2nd (4th? 5th?) checking fuel pressure. A filter wouldn't likely clog from one trip to the next. Pump might though.

WW7

the IAC wouldn't affect the "off idle" running of the engine, but it could make it stall at idle......I don't think the IAC is causing your problem...
I did however have a fuel filter, that the inside element broke loose inside the filter housing, causing the engine to starve for fuel and not start, because it partially blocked the fuel flow...All the engine would do is spit and sputter without starting......Thank goodness it happened right after installing the filter or it could have been a PITA to figure out what was wrong...The fuel filter by the way was a "Fram".....You could look through the filter and see the element moving around as you shook it....But other then somthing like this happening , Tom is correct , fuel filters usually cause running problems before clogging up to the point that the car won't run/start at all.....WW

Vic'89

How in the world can a Dealer work on a car for 5 hrs and not figure it out ?

A no start condition is a very basic problem. Not complex at all.
Does the engine crank ? Is there Fuel ? is there spark ?

Vic

WW7

A lot of the younger mechanics today are lost if there scanners/computers can't pinpoint what the problem is with a car.....Remember , these cars are 20 something years old, and the problems associated with them are not going to be figured out without the proper knowledge gained by years of working on them.....Some of the older C4s are older then the mechanics.....WW

C409

.......... Bad gas ? ...............

leesvet

where the hell did they come up with the IAC?

You need to get your car as far away from THAT dealer and their book educated "tech" as you can before they create other costly problems by experimenting and GUESSING at what they are doing !

RUN !

these wanna be's are PARTS CHANGERS. Dealers do NOT earn a dime 'fixing' cars. They pay the rent by selling PARTS.

Iac....idle air control, got NOTHING to do with starting the engine.

Your Problem is FUEL. plain & simple. The fuel system when clogged or a pump that's dying is the only thing that will not set some form of a code. there is NO CODE for a dead pump or low pressure.

verify the low fuel pressur with the test gauge ON the RAIL as suggested. Then use the info you get to go to the pump or filter, or BOTH. Its well worth your time to just go ahead and install a NEW pump AND filter,. but, PROVE the problem BEFORE digging in your pocket !

Get your FSM set. the 2 book set is cheap right now. I've seen the used books selling for $35 on fleabay. Find an older set that still has color electrical drawings. Newer ones are B&W. Sucks trying to read b&w elec drawings....too many little letters and numbers.

If somehow you DO have good pressure, 40 psi at key ON and 38 at idle...<800 rpm, the next stop would be the distributer to look for a communication problem to the ECM/inj system. Fuel injections gets its "permissions" from dist reference pulses. No signal from the dist? no fuel injection. BUT< if you DO indeed have less fuel pressure than 40 at key on no cranking, you need not look at the dist at all.

Fuel pressure is the KEY here. Your dealership, Stealerships parts changers have not even found a test gauge for that engine.......all the older guys that went to service school for TPI and LT engines have long ago retired and took their tools with them. These children in the shops these days cannot even tell you what TPI means......

good luck. get it OUT of the dealership with a tow truck if that's what it takes ! seriously !

Tom400CFI

Probably not bad gas...

JC316

Unplug your mass air flow sensor and see if it will run. My L98 IROC was acting like that and it was the MAF.

akbeaver

Go back to the basics to find the problem. Fuel, air and spark.

Confirm the presence or absence of each and when you find the missing element, investigate further.

Sounds like fuel supply may be your issue based upon your description. Filter, pump, blocked line, as has been mentioned already.

Things that occur suddenly (no warning) are usually a single failure that can be found after systematic investigation. Don't give up on the car. Things break. We fix. Have fun!!

AGENT 86

Can you start and hold a steady rpm with your foot on the pedal ?