PontiacBonnevilleClub.com

Any help with this is greatly appreciated. My 2002 SLE with 150K has been a great car. Im up to date on all service to try and keep it running 100% but this issue is driving me *shoot* crazy. No CEL on but under load she starts bucking and when the car skips more that a few seconds I get a flashing CEL.(cylinder 4 misfire) Also when it skips really bad I can hear squeaks or chirp sounds under the hood. The car has had the intake done, and in the last year it has new delco $7 plugs and wires, new cat, new fuel pump and filter, mass air sensor and air filter, throttle position sensor, fuel pressure regulator, and much more stuff. I had the tranny filter and fluid done a few years back and when this issue started i had the fuel rails checked and cleaned, coil pack swapped and others checked, and the throttle plate cleaned which I guess was pretty nasty. I wish i knew what the hell is the problem because otherwise the car runs fantastic. I also notice a fuel smell along the drivers side of the car (no visible leaks) and one weird issue it has was if the engine was warm it would usually need to have the gas pedal pressed to start. I literally just put another new mass air in tonight so im not sure if that addressed the hard starting when the engine is warm. I put the mass air sensor in tonight because last week I had a CEL come on and stay on which I scanned and it came up with the mass air code P0302 i believe. On the quick ride home after the mass air install I noticed the bucking/skipping is still there under load. I read somewhere a Bonneville owner said something about a external transmission module replacement fixed a similar issue but im tired of throwing parts at it and I figured one of you guys may have run across this before.

Check the FPR for the fuel smell? Also could be having a problem with the fuel injector for cylinder 4 for the misfiring. Just things I would think of. Good luck!

Mine was skipping/missing at highway speed, sometimes so hard it felt I ran over something in the road. Then it skipped badly one night and all the lights winked which told me the engine was physically missing a beat or two. I had installed MSD coil paks a couple years ago, but a swap back to AC/Delco coils cured my problem, but I never had the strong fuel smell issue.

Sounds like you have covered a lot of ground already, and I can sympathize how nagging problems like this can be. Best of luck, and if I were in your shoes I'd be looking for local shop that has someone well experienced with GM cars. Dealers aren't always the best.

Check the connectors for the fuel lines at the fuel rail, I have seen a few of them leak when wiggled around. As for the missing / bucking, did you replace the plugs and wires as part of the search to cure the issue? I have seen plugs bad right out of the box or fail shortly after installing them, just because the plugs and wires are new does not rule them out as the issue. I would replace #4 plug and see if that makes any difference, then swap that wire out or try to swap it with a wire from another cylinder and see if the misfire follows the wire.

The squeeks and chirps hear could be the belt slipping a little bit as when you get a misfire that brief moment surges the entire rotating assembly which causes the belt tensioner to jump around to try to maintain proper tension.

You have a flashing CEL and diagnosed a cylinder 4 misfire, so check the spark plug wire and coil pak (swap it to another cylinder and then swap the wire to another cylinder) and see if the misfire follows your change or stays at #4. If it stays at #4 Then pull the #4 plug and see if the insulator is cracked or just put in a new plug.

Check your plug wire routing on your rear three cylinders. I had the same problem after changing plugs and wires. I was chasing the same problem on my 2002 SLE. Start by removing the plug wires from there holders and separate them so they are not as close and see if this helps. That's how I found the problem. I ended up looking at a buddy's Grand Prix, routed the wires the same way in the holders and has been great since. I hope this helps. Maybe my car is just a little anal on things!

While checking the routing of the wires, make sure that all are moved away from the O2 sensor and its wiring. That has been known to cause some issues.

I've had a new ACDelco wire short through the insulator in a short time before. A few months. While it's idling in a dark place, use a spray bottle of water to shoot a mist around the wires and look for arcing. It might take some wiggling of the wires. Or you could do like I did at the time. Listen for a slight ticking in a place that doesn't make sense, lean your ear real close.... and get your head frikken shocked. lol I didn't do that twice!

It sounds like you can concentrate on the #4 wire. The terminals could be not quite tight enough as well.

Thanks for the replies. Ill check a few of those things. One thing i have maybe you guys think may be related. I have a P0102 code that popped up a month or two ago and i changed the MAF sensor and cleared the light. Anyway the code came back last week. I cleared it again and jiggled the harness but the code didnt pop back up. Do you think it could be a bad PCM? One thing I have noticed and it could be normal but when the car does its bucking/skipping I see the RPM'S jump up to 2K + once it get out of its skipping. Think this intermittent MAF code could be causing the skip? Even if the CEL isnt on maybe its not reading right and screwing up the fuel mix...