Hey guys, my 87 Vert all of a sudden just started running rough at idle and while excelerating. I have checked the resistance on all of the injectors [all same reading], replace the plugs, wires, cap & rotor and fuel filter with no improvement. I even pulled the leads off of a couple injectors while it was running and didn't see any difference. There seems to be a strong smell of raw gas but I can't find out where it its coming from. I'm assuming it is coming from the exhaust and I don't have another problem. The next thing I am going to look at is the ECM. I was told that if I disconnect the battery for a few minutes it would cause my ECM to reset itself, is this true or has anyone else tried it. I'm looking at all possibilities including replacing the O2 sensor and EGR valve. My check engine light does come on and I'm not getting any codes. Any other suggestions would be great.

 

you can reset the ECM by disconnecting the battery or pulling the fuse. Do you have a Throttle position sensor? You might check or replace that or your map sensor

 

"There seems to be a strong smell of raw gas but I can't find out where it its coming from."

I had a similar problem .. Very frustrating .. After a few local mechanics .. Replaced Fuel pressure regulator diaphragm. Rubber gets old over time. Like rubber fuel lines etc. Probably something dumb & simple.

 

before you spend big bucks changing the MAF or anything else, check for vacuum leaks, let the engine idle and spray either starting fluid or injector cleaner around the engine, spray around the plenum and runners. if your engine jumps up in RPMs you have found a leak. If you suspect the fuel pressure reg. pull the thin vacuum tube if gas drips out then you have a bad diaphram. the EGR can be tested with a hand held vacuum pump. using a flashlight to look at the spindle and the diaphram on the EGR, you should be able to draw a vacuum, and see the spindle rise up. The vacuum should hold. sometimes carbon gets into the EGR seat and prevents it from closing causing a vacuum leak.
lastly make sure you test for leaks on the carbon canister & the round vacuum resavoir. that area can give the gas smell.
test your fuel pressure you may have a problem with the fuel returrn lines they also can leak, the FSM has a test procedure for this.
Tom

 

I don't think there is a C4 without a TPS. And his 1987 has an adjustable TPS. Despite this hasty advice, don't replace a single part without first trouble shooting and locating the problem and the faulty, if any, part(s). People complain about shops that waste parts and money "guessing", and then turn around and do the same thing because they don't know haw their car works.

RACE ON!!!

 

Hey guys, I talked to the mechanic that has been taking care of my car for the two previous owners and I told him what was happening. He told me he can almost guarantee that I got a bad tank of gas. I did fill it up the day before and my tank was really low which is something I normally never let happen. He suggested I get a bottle of HEET and put it in the tank to absorbe the water. I just did and wanted to see if anyone else ever used this stuff and if it worked. If water is the problem I do not want to pay someone to drop the tank and clean it out. Opinions please.

 

You might want to check the fuel reg vacuum line for gas, and check to see if the cold start valve is receiving power, well after it should have timed out.

 

Exactly right. Spending money needlessly, you'll end up hating your Corvette. Buy a Factory Shop Manual, read and you'll know how to diagnos this problem and ones in the future. Oh, and fix these problems yourself too.

 

'heet' is just 'dry gas', mixes with water and lowers freeze point to reduce freeze/plugging of fuel lines...then you hafta drive long enuf to 'run out' the contaminated mix...some 'drygas' formulations may react negatively with the liner in a c4 fuel tank or other fuel system components...i don't advocate use of any additive...most gasoline vendors sell 'summer' or 'winter' gasoline as received from their supplier, sometimes weather varies from supplier prediction, etc ( 'summer' formulas may cause poor performance at low ambient.)

to drain my tank, i first move the car OUTDOORS, second check that fire insurance is in effect, I do NOT recommend that you do this yourself...then remove the 'schrader' valve core from the fuel rail test port and attach (CLAMP) a hose leading from the test port to a remote,large 'gasoline can'...at the ALCL, aka ALDL (just above operators right knee when sitting in driver seat), jumper a FUSED 12v feed into terminal G (lower row, furthest left) to run my in-tank fuel pump... observe gas can closely to avoid overfill/spill/explosion...listen for pump sound to change pitch when fuel is emptied below pump intake and IMMEDIATELY remove 12v power to pump to avoid murdering in-tank fuel pump...add 5 gal of new/known good gasoline to tank and run pump/drain tank till 'empty' to remove last traces of contaminant...repeat: DO NOT TRY THIS AT HOME.

water can often be removed from gasoline by 'straining' the mix thru a genuine (no synthetic sub) 'chamois' leather as commonly used back/day after car wash (check chamois for holes or sewn seams which will allow water to pass), making it suitable for lawnmowers,etc...some gasolines may contain additives that destroy chamois skin.

DANGER: GASOLINE IS VERY DANGEROUS AND ITS FUMES CAN TRAVEL LONG DISTANCES AND EXPLODE WITH SEVERE INJURY AND FATAL RESULTS.

 

If the SES light is coming on a code is being set. That is where you have to start. "Reseting" an ECM does essentially nothing excepl erase all the BLM settings which must then be relearned.

 

Heet is alcohol. Don't now what dry gas is.