I drove the car today on a 2.5 hr roadtrip and car ran beautiful. I came out 5 hours later and the car had a very rough idle like a vacuum leak. I'm pretty sure this isn't the case as I have just redone all the vacuum connections chasing a stuck defroster. I have also changed the purge valve in that whole process.
The car has had new coils installed, e3 plugs and new wires within the last 5K miles. Trans vacuum modulator was also replaced with trans flush and new filter.
It runs like crap and on the hills out on the highway, you could really feel it shuddering but my guess is a dropped cylinder or something.
Oh, I have replaced the MAF and also the Idle speed sensor. I think I also changed the idle air control valve but not certain on that? I also changed the O2 sensor as well and the computer within the last 5K. Yes, it has a lot of new parts on it and I'm sick of this money pit already!
The check engine light would come on for like 10-15 seconds and then go out. That happened about 3 times in the 2.5 hr trip home.
Any ideas would be greatly appreciated. It'* just weird how it started doing this all of a sudden!

Okay, after scanning the car, I am getting:
DTC: 26- Quad Driver module or Quad-driver No. 1 error
DTC:59 Transmission fluid temp low
DTC:44 Lean Exhaust indicated (left side on dual oxygen models)

I've chased this darn Quad driver code many different times and it is stumping me!

When I unplug the IAC the motor seems to idle better but I don't think I can drive it this way?

SOLVED!!!!
I replaced the IAC valve because it looked rather marginal at 180K as well as the ignition control module. Still didn't change a thing so I grapped a pair of insulated pliers and pulled the spark plug wires one at a time from the coils to see if anything would change, double checking those new cheap-*** ebay coils I bought 5K miles ago. Low and behold, the middle coil was only throwing juice out of one tower! New Autozone coil later and it runs like it is ready for the "street class" at Byron Dragway!
I'm not all that upset that I spent $226 on parts I didn't really need because I look at it as preventative maintenance at this point based on all the posts dealing with bad ignition modules...
I'm a happy camper again!

I personaly, have heard too many horror stories when it comes to cheap ebay chinese garbage.

I'm the same way, if I spend $100 on parts that didn't fix it, well, at least I don't have to worry about those parts for awhile.

Glad you got it fixed.

Well, back to the shudder again. 8-( I was on the way home from a visitaqtion and the darn thing started missing again. I pulled into Zone 1 and bought the other 2 coils and replaced them in the parking lot, think, well maybe the other cvoils went bad too. I'llscan it tomorrow but it seems like there could be a loose connection or something. On a bumpy road coming home, I noticed for a split second it ran smoth when I hit a bump. I've heard about the O2 sensor wire on the plug wire as an issue so I'll check that. The only other thing I haven't replaced is the knock sensor or the fuel pump at this point and the crank trigger....I'm totally frustrated and it is my regular driver needed for ministry use as a chaplain. Anyone got some ideas?

I moved the O2 sensor and the car ran fine for like a day and then today, I drove it like 7 miles, shut the car off, came back out to car roughly 2 hrs later, and whala....missing like crazy, no acceleration, and shuddering when trying to climb any hill. I replaced the coils, ignition module, IAC, TPS, O2, MAF, Purge valve solenoid, computer, plugs, wires, vacuum connections all redone, new PCV valve, trans filter and fluid 5K ago....
The other night, after replacing 2 coils in the AZ parking lot, the car would crank over but not start. Then after I opened the door, and tried it again, it started. After I moved the #6 spark plug wire from the O2 wire yesterday, the engine idled higher than normal as well. No CEL currently so I'm kind of wondering if this could be a fuel related issue. Could a bad fuel filter cause this type of surging or a bad fuel pump? I read in a different post where Justin suggested a clogged strainer as well, which somewhat makes sense but this has seemed more elctrical up until now as the CEL was on continuously. Could the computer be bad already? I had a bogus scanner that had a blown motherboard that was plugged into the computer at one time so I'm wondering if that could have done something? I'm reaching at this point! I heard this 92' 3800 doesn't have an egr either so I ruled that out? New Cat on the car also. crank trigger issue possibly? Knock sensor? those are I believe the only things to which I haven't changed yet....I just don't get it...Three of us are having what seems to be the same issue and it'* like GM programmed these cars to do this so we would be forced to give up and buy new but this grad stdnt can't roll like that yet!
Any help would be oh so appreciated. Surely someone out there has had this issue and found the fix by now????

Hi, The scenario above is everything I have done up to date and this morning, when the car was started cold, I got what others are referring to as a "High idle" scenario. Car seemed to idle okay but I didn't drive. Rather, I pulled the codes which are:
DTC 59= Trans Temp Low
DTC 13= O2 sensor signal fault too low open left O2 sensor circuit
DTC 26= Quad Driver Module 1 (Which I have been chasing since day one)
DTC 59= Trans Temp Low

In my mind, the QDM1 is controlled by the computer itself. Given the fact that a blown MB Innova scanner was introduced to the current PCM, even though it was new, I think it may have hurt it. I don't know how else to explain. The )2 sensor was already replaced and the wire is tucked out of the way. All the coils, ICM, Plugs, and Wires were changed 5K miles ago.
I think it is time to visit AZ this morning and get a computer and a O2 sensor just to be safe.....I'll update after I try those....

I swapped the computer and didn't change a thing. good thing that was under warranty! Fuel pressure is at 37 lbs, which seems low to me? Changing filter and O2 sensor next....

Changed the O2 sensor...no change
changed fuel filter...got pressure up to 39 psi from 37psi

Went back to parts store and swapped middle coil to top coil. miss traveled with coil. Replaced coil and runs normal again but ran codes again after trip home.
Still getting DTC 26 QDM1 and now have DTC42 -Electronic Spark Timing (EST) circuit - open or shorted....????

Could someone please try and review what I have done and give me some sort of input if you have any. In meantime, I'll scan for DTC 42 issues here on the site...thanks!