I'm having some issues with my '99 Coupe and I wanted to run it by everyone before I start tearing things apart.

I've noticed the car has started stumbling on acceleration at random. Let me go into how I've gotten to this point...

A while back I noticed a fairly strong unburnt fuel smell after I'd been running the car hard. I decided to swap out my NGK copper plugs (that saw a lot of abuse on the racetrack) for the new GM Iridiums. Before I could do that, I had to stop driving the car for four weeks while I was in a cast. I disconnected the battery during that time. I figured a computer relearn couldn't hurt either.

Once I started driving it again, the problem cropped up. There are no current codes.

I have a ProFlow airbox with K&N filter so I was going to remove and clean the MAF. I'm still going to do the plugs as well. Can anyone think of other things to check? I guess I could clear the computer again and do another relearn as well.

I also just noticed a possible alternator problem. I've noticed it sometimes takes some time for the voltage to come up after I've started the car and it seems to sag pretty bad at times (down from an idle at 13.9 to 12.x) when the engine bogs. Think this could also be part of the problem?

Thanks!

Mike

 

I had the same thing. I clean all the grounds on the sensor and relays. I
hope this will help you. It worked for me. Every time i would take off it
stumbl, like it was running out of gas. My voltage all so was down
from 13.5 to 12.8, i put a voltage metter on it and it showed 13.2. SO
check your voltage.

 

When did you last change your fuel filter???
similar syptoms...
Did you damage a plug wire during the plug change by yanking on the wire instead of the boot ( getting intermittent firing based on engine vibration)?
Clean your MAF with electrical contact cleaner, clean the grounds mentioned by Jack. Check you plug wires for proper seating and damage

 

I'll take a look at the grounds. Plug change was 10,000 miles ago so unless something failed, I doubt that had anything to do with it. I can check the fuel filter but with only 22,000 miles on the car, one would expect that it would be in good shape.

Thanks for the feedback!

Mike

 

Given you have a K&N filter, I'm betting oil from the filter has gotten on your MAF and screwed it up. That happened to me and I ended up having to get a new MAF. Then the car ran perfect.
Good luck!

 

Well, well, well, well well...

I took some time today to look things over. Lo and behold, I found two coil packs with corroded terminals. Interestingly enough, it was the second coil from the firewall on both sides.

I pulled all the wires and one of the spark plug terminals (Taylor wires) came right out of the boot (same cylinder as one of the corroded coils).

Well, in for a penny, in for a pound! I pulled all the old plugs and swapped them with new GM Iridiums that I had. I pulled the two coils and cleaned the terminals as best as I could. I then put back on my stock GM wires.

The wires do not snap when connecting to the two coils that were corroded. I'm guessing I should replace them, eh?

It's warming up right now and then I'll take a run and see if the problem has gone away. Still, with those damaged coils, it may not be fixed yet.

So much for working on the intake tract!

Mike