Hi,

I am new to the forum and am hoping someone can help with a couple of issues I am having with my SSEI.

First one is that sometimes at a stoplight, the RPM'* will suddenly drop and the engine "stumbles" - almost seems like the car might stall, but doesn't. Have had it to the dealer and independent garage and no one can figure out what is going on. There have been no check engine lights. One thing I have noticed, it seems that it happens more frequently if the AC compresor is running.

The second item is a slight vibration in the front end. Tires are balanced correctly and alignment is ok. One possible theory that was floated by the gagrage is wheel bearings.
I am the original owner and the car has 58K miles - seems soon for bad wheel bearings.

Also, I am installing a Pioneer AVIC Z1 in dash nav unit. Will post pictures when done.

Thanks.

As for the stumble. Causes could be a vac leak. Check all lines by spraying carb cleaner on al lines and connections, don't forget the EGR tube. Also, check all plug wires. One thing that comes up from time to time is a plug wire being to close to the O2 sensor wire So check the rear set, wires 4 and 6 are good for this. You can also pull all plugs and inspect them. Look for any fowling. You can also pull the coils and inspect the connections.

Now for the vibration. Do you feel this more when braking? It could be a warped rotor. A bearing would make a fair amount sound. Do you feel more vibration when cornering?

One last thing. Welcome to the club.

Another possible issue with the stumble might be a crankshaft sensor. We've seen these make the engine cut out and restart at almost the same time. Causes what feels like a hiccup in the motor.

One way I've been able to pinpoint it was using a scan gauge or tool to watch the run time counter. If it resets to 0 after the stumble..the pcm saw a stall and restart..even though you never touched the key.

Thanks to everyone for your replies. They are greatly appreciated. Will start looking at what you have recommended and hopefully can get to the cause of the problem.

Meant to respond sooner but have been out of town traveling on business.

Is the stumble real intermittent? If so, it seems to be a somewhat common occurrence with the 2000+*. Mine will do it maybe once every few months.

Another common problem is vibrations, that there seems to be no one solution for. People have replaced virtually every front suspension component, as well as the hubs, without solving the problem. A couple have said replacing the axles has helped.

Archon.. didn't you find a stumble in the engine to possibly be caused from a poor battery ground for the negative cable?

Yes, I did - but that occurred at highway speeds, in OD with the torque converter locked up, around 2k RPMs. Lightly stepping on the gas would cause a jerking where you could see a 200 RPM variation in the tach. It idled fine. The car that I found that problem on will also do the occasional stumble at a light. It happens shortly after coming to a stop. The rpms will drop to 500 - 600 momentarily, then up to around 950, then settle back down to normal. This all happens within a couple of seconds. It doesn't do it often enough to investigate the cause.

the stumble could be do to a descreened maf or the screen being messed up. if the screen is missing from the mass air flow meter it will cause the air flow meter to surge and make the car stumble.

Just wanted to clarify that the stumble occurs when I am at a red light or waititng with my foot on the brake. Again, it will be ideling fine then suddenly a drop in the rpms and a stumble.I do not detect it at all at highway speeds. There also seems to be a correlation with when the AC Compressor is on - more noticeable.

FWIW, with the surging that Bill asked about, the problem was found to be a rusted, corroded connection on the negative battery cable where it is bolted to the floor pan. The threads of the bolt and in the floor pan were quite rusted. Cleaning things up eliminated the problem.