95 LeSabre Misses During Heavy Throttle

I kindly ask your assistance in diagnosing a strange problem that just surfaced.

Whether I push down on the gas pedal in park, or while driving, the engine misses. It is constant, not intermittant. Car has 84,600mi. It just started. It does it cold or hot. If you are traveling down the highway, it may or may not miss (mostly does not). It mainly misses only when accelerating.

There is no check engine light, though I have not checked the computer for any pending codes.

I've verified good spark on all 6 cylinders at the end of each spark plug wire. Spark plugs, wires and fuel filter were changed 25,000 mi ago (5/17/07). The metal inserts on 2 of the plug wires have become disconnected and stayed on the plug heads when I pulled the wires off, but I honestly don't believe this is the problem since good spark was still verified.

I've cleaned the air temperature sensor and the MAF sensor. The MAF was a bit dirty. No change.

I'm wondering if fuel delivery is the issue. Though I changed the fuel filter only 25,000 miles ago, it was 5 years ago, and not sure but I believe it is a Fram filter. I recently discovered a Fram filter on another car of mine apparently rusted out inside. I'm wondering if the same thing happened on this car.

As you can tell the car is driven on average less than 5,000 mi per year.

What is the likely problem here??

Thank you.

You'll need to replace the damages wires. Pull the wires off the coils and check for corrosion. You can have a helper "load" the eng, while you use a spray bottle on heavy mist and spray all the wires and coil with water and check for spark jumping to ground anywhere. If it's been a while since you did a tune, you may want to replace the plugs and wires anyway, and fuel filter/air filter while you are at it.

I'm guessing the plugs aren't the problem since there is only 25,000mi on them. They are Autolite platinums. -????

There is no corrosion on the ignition modules.

I checked all fuses under the hood and they are all OK.

All vacuum hoses are connected and seems OK.

I changed the fuel filter. The old Fram filter seemed restricted a bit. Changing the fuel filter made no difference. The car still heavily misses under medium and heavy acceleration (whether the engine is cold or hot). You can sometimes feel the power come and go like it misfires-misfires-misfires-fires-misfires...


Living here in humid Florida and the car not driven much I'm wondering if water in the fuel could be the problem, but I am guessing no.

I am also wondering if the PCM has become faulty again. It was changed 5000mi ago due to very bad engine performance including missing and etc. The engine is not missing nearly as bad this time though.

hmmmmmm....

I finally figured out the problem.

I put on new plug wires but that had no effect.

I started to do some hard-core research in the forum when I ran into a very similar description of my problem. It turns out that I was the author of that problem, D'oh.

The problem has happend to this car before. 18 months ago the 6-3 coil pack was producing very weak spark, and when I replaced it, the car ran fine again. Today, I noticed that both the 2-5 coil pack as well as the 4-1 coil pack were also producing weak spark so I replaced them both, and voila, problem solved.

This just goes to show you that sometimes components fail in sets. If I had to do it all over again, I would have replaced all 3 coil packs 18 months ago when the 1st one became faulty. That would have saved me 2 days of aggravation.

Glad you got it figured out... If you ever have to do this again, Look for the newest supercharged 3800 you can find( 97+ ), you will be looking for coils that have a Blue strip on the bottom.

Ignition related issues can be hard to track down sometimes..lol

I've verified good spark on all 6 cylinders at the end of each spark plug wire.

Yet you replaced two coils.....okaaaaaaay.....