Hi, gang. As usual am coming to to those who know because mechanics
don't. A few weeks ago was heading home from 100 miles away. Shortly thereafter the car started running rough. Like it was missing or the timing was off. Drove 70 miles and stopped to check under my hood. Could see nothing amiss. Cranked it, still running rough and drove another 15 miles. The car stalled.

Had it trailered to Chev. Dealer. Told me it was ready in a few days after replacing spark plug wires. Did not get 100 yards and realized it was doing the same thing it did when I left it. Turned around and took it back. They replaced the engine computer module. I picked it up and it up and drove less the 20 miles 2 or 3 times, ran great. Drove to town and back 25 miles, loaded it up to leave for the weekend. When I pulled out of my drive onto the hwy I started accelerating she started hesitating and then began doing exactly what it was doing when I took it to the shop.

Took it back to the shop and they replaced my distributor. He called and said it was running good but was going to keep and drive it a cpl of times before I picked it up. He called me the next day and said when he drove it the third time it sarted doing it again. They do not have a computer reader for the car and they are stymied. ( mechanic wanted me to tell you that the fuel pressure can be read and is good but they can't measure the volume)

If you have any experience with a problem like this I need your help, please.

Lan

 

I would look into that further. Those symptoms scream fuel filter...

It takes someone that has seen it, done it, been there to use a pressure gauge and diagnose a filter or sock problem.
The way the needle on the gauge behaves is just as important or more than the pressure that it shows...(which should be approx 40)
A flickering needle of more than 1 or 2 psi spells flow problem. The flow at idle should be rock solid. The flicker indicates trash moving around inside the filter. When its "just right" it'll plug everything and cause the engine to burp, backfire, stall, and die. Might be 2 minutes, 2 hrs, it'll fire up again after the pressure drops and the trash floats away from the filter screen, and the car runs right again.
See if they will once again look at the pressure and even tape the gauge to the windshield and go for a good drive. The gauge should always show a steady needle, that can move but not flicker quickly and bounce around quickly when the engine is at a steady rpm.

If there is no Joy there, look at the grounds, especially the G-104 bundle near the oil filter.

 

A Chevy dealer that doesn't have a "computer reader" for a Corvette? Nice! Sounds like an intermitent fuel problem. I'd guess pump, but you need to have a gauge hooked up when the problem happens. Then again what do I know, I'm a mechanic.

 

You'd be surprized at how hard it is to find a dealer with OBD-I scan technology....Most upgraded to OBD-II that are so new that they don;t even accept OBD-I data...plus, nothing.

The only shops that still keep their OBD-I scanners are Corvette shops or muscle car shops.

The way these dealer guys look at it, is that they will be spending 95% of their time on late model warranty work, or continued service on cars that are somewhere less than 20 yrs old (all OBD-II)... Statistically they are right...My ECM is older than most of the techs at a dealership...But so is the space shuttle..

Try finding someone that can scan OBD-I ABS off-board..

 

If your 89 has the original fuel injectors (Multecs have a gray colored
body), they can cause the problems you describe.

The coils inside the injector are exposed to the fuel. The
coil insulation eventually breaks down and the windings
short out causing the injector to not function properly.

Four injectors are on the same circuit so one with a shorted
winding can cause problems for the other 3.

Have the mechanic check the resistance of each fuel injector
coil both when cold and hot. They all should measure around 16
ohms. If one injector is bad, replace them all. If only one
injector coil is bad, you can unplug its connector and run on 7 cylinders to get the car home.

Here's FIC's video that shows defective Multecs.

http://forums.corvetteforum.com/c4-t...atch-this.html


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You can download OBD-1 diagnostic software free on the internet (WINALDL or TUNER PRO). Then you can purchase a $65 connector to go from the under-dash OBD-1 plug to your computer and then read and diagnose problems yourself. Check it out.

 

Fuel injectors are bad.

 

They will also knock out the ECM injector driver and there will be no pulse to all injectors.

 

Thanks for that link...
I have been planning on getting a laptop dedicated to diagnostics on the C4... just hav'nt found a way to slip that in the budget as of yet. I'm not as sneeky as a U.S. Congressman.

I was also considering buying all the stuff needed to reflash proms, so I could tune or make them as needed. Again, gotta hide that purchase somehow.

Do you know if the ABS programs are available to download?
Thats the one that worries me...since its offboard and that particular system was only for a very few yrs, its pretty much obsolete.

 

sounds like what mine was doing turned out to be injectors CALL JON ate FIC

 

As always, I appreciate your input.

 

Seems to me that injector problems would not "go away" and come back later. (though stranger things have happened, I am sure) You might check the 2 injector fuses in the fuse box and make sure the connections are scrubbed clean. Each fuse runs one bank of injectors, they are labeled INJ1 and INJ2. Easy to check.

 

I too have experienced similar problems, but only when the engine has been operating at higher temperatures (not overheating but over 200 degrees). Any thoughts on this?

 

Usually act up a little more when they are warm until they are just plain not working at all. Replace them before one sticks open.

 

Could be injectors but it really sounds like how mine was acting when the fuel pump was on the way out. Once it started to warm up it would miss and run like crap then it would just die. Left me 60 miles from home.

Racetronics has a nice package deal.

 

Need more help about this. Dealer spent some time searching for my problem. Decided that the ECM module I had replaced had gone bad and put in another one. Ran fine for 30 miles. Second time I drove it it started cutting out if I put my foot in it. Decided to go the 30 miles I had planned because I had not driven it in so long and hoped it would straighten out. It ran ok at 65 but did not want me to accelerate.

When I cranked it to go home. Would accerate up to 63 and become completely unresponsive. Would caost down to 48 miles per hour then catch up and accelrate to 63 then quit responding at all till ig got down to 48. Sometimes could drop to 5th gear and it would respond until I got to 63, then same thing again.

ANY IDEAS?

Lan

 

bump

 

This worked for me....Jon is the man. My 89 ran fine when cold, (open loop), but when warmed up, after going into closed loop, I think at about 130-140 degrees F, it would tend to skip, especially at idle.
Good Luck

 

http://forums.corvetteforum.com/1577540258-post8.html

 

If you're replacing Ignition Modules - in the Distributor - and not the ECM (under the Dash) then you're not using the right grease as a heat sink. Dielectric grease - or nothing at all - will just cause it to overheat and burn up. Use the stuff that comes with the replacement module.