tmhd2 Posted October 31, 2009 Report Share Posted October 31, 2009 Hi everybody I searched the heck out of this and I'm just not sure if I'm barking up the right tree or not... My 91 Regal with the infamous 3.1 motor is getting progressively worse with a frustrating stalling problem. It started when I was sitting at a long red light one day. I felt a shudder, looked down, and the tach was reading 0. Hmm. Stalled? WTF? Started it up, drove off, and all was fine for a week or so. Previous to this issue, the car ran great. It does have a new TPS as of a month ago. At that time I also cleaned the IAC and did an idle relearn. Last week, it stalled again under similar circumstances. I started it back up, made it to the next light, and it stalled again. Hmm. I decided at this point that it was not an anomaly and I should probably pay more attention to it. What I noticed, is that just before it stalls, the tach signal is erratic. It seems to show a very high reading for a split second just before the motor dies. It is a digital tach so it is hard to be certain because the numbers flash by so fast. The problem has now progressed to a point where even as you are driving down the road the motor is missing and jerking very badly. The problem seems to get worse the longer the car is driven. It can take anywhere from a few miles to an hour of driving for the symptoms to show up. I initially thought that it would be the crank sensor, since that is where the signal originates, but everything that I've read about the failure symptoms people are describing here seem to indicate that when they fail it is either once and for all and the car doesn't run again, or it has to cool down before restarting. Mine ALWAYS fires right back up. For the record, the crank sensor is about a year old. I also checked the wiring and I do not see any frayed or bare spots. It passes the shake test with the car idling in the driveway. I don't think it is the wiring because wiring wouldn't really tend to cause a condition that gets worse with temperature / run time. My next thought is the ICM. I have never replaced it in the two years i've owned the car, so its age is unknown. I know the previous owner, who owned the car 7 years, and I don't think he replaced it either. It passes the smack test and all of the connections are tight. The only other thing I can think of would be the ECM, which also passes the smack test. I took it apart and inspected it for loose solder joints, etc. Everything looked good. ECM is original. Any input on this situation is much appreciated. I need to count on this car for a while yet and need to get it fixed before it kills me stalling in the middle of a left turn... Thanks in advance! Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 31, 2009 Report Share Posted October 31, 2009 there is nothing infamous about the 3.1 other than being completely gutless in a car as heavy as a W... has it thrown any codes? Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted October 31, 2009 Author Report Share Posted October 31, 2009 Thanks for the quick reply. My 3.1 is just special I guess. I got the car late in its life and needing a lot of TLC... I know they're reputed as being a very reliable engine. It has not thrown a single code. I have tried pulling them by shorting the two pins together and nothing shows up. I don't have a OBD 1 scanner so I haven't gotten any further into it. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 31, 2009 Report Share Posted October 31, 2009 by nothing, do you mean just code 12 or not even that? if nothing at all comes up, there is bad wiring from your ALDL port to the ECM or the ECM itself is FUBARed. Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted October 31, 2009 Author Report Share Posted October 31, 2009 It is Code 12 Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 31, 2009 Report Share Posted October 31, 2009 know how to test injectors? and the coils themselves? Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted October 31, 2009 Author Report Share Posted October 31, 2009 I tested the injectors a year or so ago when I had the upper manifold off for other reasons and wound up replacing one that was shorted. I was low on $$ or I'd have had the whole set cleaned and flow tested. I haven't done anything with the coils yet. Will a bad coil pack cause the tach reading to jump around? Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted October 31, 2009 Report Share Posted October 31, 2009 possible, but the ICM itself is a little more likely to cause that specific issue. but testing the coils takes all of 30 seconds each, so i figured, why not? Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted October 31, 2009 Author Report Share Posted October 31, 2009 Good point! I'll definitely test them when i get back to where the car is. Thanks a lot for the 3rd shift diagnostics Quote Link to comment Share on other sites More sharing options...
Crazy K Posted October 31, 2009 Report Share Posted October 31, 2009 thoughts: weak fuel pump or clogged fuel filter? bad injectors? they should all be in the 12 ohm range... Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted October 31, 2009 Author Report Share Posted October 31, 2009 Fuel pump and filter are both from 2008 and the pressure tests good. I checked the injectors around that same time and they were all good except one had a bad coil. It was replaced. Quote Link to comment Share on other sites More sharing options...
Mach 5 Posted October 31, 2009 Report Share Posted October 31, 2009 Vacuum leak? Would cause the stumble, random misfire and the erractic tach. Quote Link to comment Share on other sites More sharing options...
dylan1630 Posted October 31, 2009 Report Share Posted October 31, 2009 Mine used to stall every time i came to a complete stop, i would have to hurry up and put it in park to keep it running but i usually couldn't do it in time. I replaced the oxygen sensor, idle air, EGR valve, and new spark plugs and wires. The thing that did the trick mostly was the O2 sensor though. Just throwing some ideas in i don't know if they'll help or not. Right now my Grand Prix is having a problem, the transmission shutters when i'm accelerating, but not when i am at a stop and take off. Disconnected the modulator, it didn't shutter. Got a new one, it shuttered, and we adjusted it and you barely feel it now, but you still can. We had to adjust it so it shifts harder in order for the shuttering to get better, but it's not gone completely :/ Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted November 1, 2009 Report Share Posted November 1, 2009 A failing ignition control module will often times do exactly as you've described. You can remove it and have it tested at most major automotive part stores for free. Make sure they test it 2-3 times in a row so it heats up some. A lot of times, they will work ok when cold, but when the car heats up, they start to have problems. Quote Link to comment Share on other sites More sharing options...
tmhd2 Posted November 2, 2009 Author Report Share Posted November 2, 2009 I feel like the module is probably my #1 suspect at this point. I won't be able to tow the car home for a few days, so I won't have an update right away. Thanks to everybody who gave me suggestions! Quote Link to comment Share on other sites More sharing options...
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