3.1 engine starts bucking

I am trying to help a friend with her Lumina, its a 96 I believe. It runs fine but after a while it will start bucking hard and she just gives it gas and sometimes it goes away, other times it will not go awaya nd when she shuts it off it won't start until it cools down. When it starts bucking the upper intake gets really hot, but under normal conditions it is not that hot. I ran my OBDII scanner on it and it pops up a code for the )2 sensor voltage, but its a stored code, not a current one. When it starts bucking it doesn't always give a CE light, and the CE light does not stay on so I am thinking the code is not realted to the issue.

I heard you can test the coil packs, how do you do this? I also have been reading the ICM can go bad, is there a way to test them? How much are replacement ICM's? The problem is intermittent but when it happens the car is not really driveable, any ideas on some tests I can do to figure out the problem?

Had a similar issue with my 91 cutlass, however on a much larger and more severe scale. The ICM can very well be the cause, though I'm not familiar with any way to test them. Advance might be able to? They're not cheap, mine was $180, but pretty easy to get to (compared to my 91). I'm fairly sure Advance can check the coil packs, if they do then great.

The first thing to do is to get a fuel pressure reading. Then if its ok spray the coil packs with water andlook for any arcing also do the ign wires

If all the other tests fail to show a fault, check the EGR valve and see if any of the valves are sticking.Doing so requires a metal gasket that will cost you about 3 bucks.

I've had a similar problem for about 2 yrs, that kept getting worse. I have a 1992 Lumina APV, 3.8L, 4T60E Auto Trans. 132K miles.

It would start up fine when cold. After it warmed up, it would die on the road. I found that if I waited at the side if the road, it would start again. I flashed the check engine light and found no trouble codes. I suspected spark or fuel, but always had it when I checked it at home. Also, when I got on the freeway in 3rd or 4th gear, the engine/trans would buck and hickup and randomly stall for a split second when the torque converter would lockup (TCC solenoid). I thought I may have more than 1 problem going on.

I removed the ignition module thinking that may be causing the stalling problem and had it tested several times at a local Autozone parts store. It passed every time. No progress on the stalling.

So I switched problems and focused on the bucking. Having read before that sometimes the TCC solenoid goes bad, I inquired at the AutoZone about a TCC for this car. The counter salesman said he did not sell this part and the only part he sold was a vehicle speed switch. He then said "sometimes the motor will stop if this sensor goes bad". I bought it, $45, and installed it. It goes in the tail shaft of the trans. I noticed, when I pulled the old one out, it had a build up of band/clutch debris on the face of the sensor pickup. I installed the new one anyway but the clutch debris accumulated on the pickup face could have been the whole problem with the VSS sensor.

Now the van does not buck and has not stalled for a couple weeks. I would have never guessed this one.