Corsica intermitant miss

[MONKEYMAN]

Parents have a 1994 Corsica with 3.1 motor with automatic. Few years ago my Stepfather said engine had a slight miss when going up the hill and light throttle. So, after over a year he decided to try to address this issue. First, he ran Techron several times. He said it helped. Fuel filter replaced. New plug wires did not solve the problem. Then local mechanic said it was the coils. Well, he replaced all three coils. It made the problem worse shortly after each coil was replaced. My stepfather finally had the plugs replaced a few months ago. It solved the problem, but now it seems to be coming back. You will be going up a hill and there is a slight jerk once or twice, then engine runs smooth. Any suggestions? FYI The high school auto mechanics teacher that replaced the plugs wanted to check them out again. I am not sure about gap of plugs. I have seen 0.060 and 0.045. Not sure which is correct? Could the gap being too wide be part of the problem?

 

[EricF]

Well the gap should be .060" according to my spec book.

Has he tried cleaning the mass air sensor??
is check engine light on?
chances of those coils being bad was a shot in the dark IMHO.

 

[MONKEYMAN]

Mass air sensor has not been cleaned. How would you do that?

No check engine lights.

It is a small town mechanic. He convinced my stepfather it was the coils. Funny thing is it would work briefly, then car ran worse then ever. He would take it back, and another coil would be replaced. It took three visits to the mechanic and $570.00 to get all the coils replaced. Then he was pretty much back to where he started with the missing.

 

[EricF]

If the MAF sensor wires are dirty, as they heat up, and get cooled down their resistance changes, however if they're dirty, the resistance will be different and will throw the car computer off. the OBD-I computer isn't smart enough to know something wrong.
Get a can of Mass Air cleaner spray from CRC, it's a grey can. DO NOT use carb cleaner (it's to harsh).
I would try cleaning the heater wires on it first.

As for the coils.. well.. depending on the brand.. they could've been bad out of the box too. Replacing those coils takes literally minutes...

Make sure you're using the correct plug.. I've used Autolite Platnum's in my Mom's 95 Beretta 3.1 (2 door corsica clone). and the car ran like a champ..
when she sold it, this kid down teh street bought it and it had some oomph to it.. he raced a 5.0 Mustang and beat it! And 2 bottles of Greased Lightning transmission additive fixed the slipping!

 

[MONKEYMAN]

Plugs were Standard ACDelcos Part No. R44LTSM6 . I have Alldata but it does not show MAF Sensor location. Where is it located?

 

[onion]

A '94 Corsica doesn't have a MAF sensor. So cross out that one.

I had a '94 Corsica for over a decade- until the transmission died back on September. And what you're describing sounds exactly like an ignition problem of some sort. Mine behaved similarly with bad wires. And my '01 Lumina with the same engne missed similarly when I had a spark plug with a cracked insulator one time. I also had a '96 Olds Achieva with the same engine- and it missed exactly like that when the coil terminals where the plug wires snapped on where corroded.

I know you've had all this work done- but based on what you've described, I still suspect the secondary ignition system. In your shoes, I would go through the ignition system with a fine-toothed comb. I'd pull the plugs, closely inspect and gap them. Inspect the crimped-on terminals on all the plug wires (both ends). Make sure they're crimped on good and tight, and check for corrosion on those ends (these engines are real bad about making corrosion where the plug wires snap on to the coils). Also check the resistance of the plug wires and make sure they're all fairly close. Remove each coil, check the resistance of the primary and secondary windings, and check their connections with the module. Also check the wiring and connectors between the crank sensors and module.

Do all that properly and I'd bet you'll find your problem.

 

[EricF]

my bad.. there is no MAF.. I was supposd to think of MAP sensor, but you can't exactly clean those... sorry!

 

[MONKEYMAN]

Originally Posted By: onion
A '94 Corsica doesn't have a MAF sensor. So cross out that one.

I had a '94 Corsica for over a decade- until the transmission died back on September. And what you're describing sounds exactly like an ignition problem of some sort. Mine behaved similarly with bad wires. And my '01 Lumina with the same engne missed similarly when I had a spark plug with a cracked insulator one time. I also had a '96 Olds Achieva with the same engine- and it missed exactly like that when the coil terminals where the plug wires snapped on where corroded.

I know you've had all this work done- but based on what you've described, I still suspect the secondary ignition system. In your shoes, I would go through the ignition system with a fine-toothed comb. I'd pull the plugs, closely inspect and gap them. Inspect the crimped-on terminals on all the plug wires (both ends). Make sure they're crimped on good and tight, and check for corrosion on those ends (these engines are real bad about making corrosion where the plug wires snap on to the coils). Also check the resistance of the plug wires and make sure they're all fairly close. Remove each coil, check the resistance of the primary and secondary windings, and check their connections with the module. Also check the wiring and connectors between the crank sensors and module.

Do all that properly and I'd bet you'll find your problem.


Thanks. I think taking it back to the high school mechanic would be better. There is no charge for labor there. I do not have time or experience to check all those possibilities.