'92' stalling and speedometer reads 0

I have a 92 regal 3.8 v6. The check engine light was intermittently coming on and the car was idling rough and stalling. I braught it to a mechanic he checked the codes and replaced the throttle sensor. I took the car and it was still doing it. I only got stuck once last week but the battery was dead. I put a new battery and I think the charging system is working I have 14.5v at the battery with the car running 12.5v with it off. Now it the stalling and rough idling is still intermittent but it only does it when the speedometer malfunctions it will always read 0. Then the car will surge the check engine light will flash and the speedometer starts working the car then runs smooth with no stalling. This can flip flop as often as every few miutes. The codes it is showing now are 21 and 43. I checked the ecm connections, clean and tight. Could this be a transmision speed sensor or an ecm? Oh! also when the speedometer is not working I cannot get any codes it will not even blink the 12 code. One time when I was checking the codes the light just stopped flashing in the middle of a code. Whatever it is it happened as I was checking the codes with just the key on? Sure enough, start the car and it was rough again.

I have a 92 regal 3.8 v6. The check engine light was intermittently coming on and the car was idling rough and stalling. I braught it to a mechanic he checked the codes and replaced the throttle sensor. I took the car and it was still doing it. I only got stuck once last week but the battery was dead. I put a new battery and I think the charging system is working I have 14.5v at the battery with the car running 12.5v with it off. Now it the stalling and rough idling is still intermittent but it only does it when the speedometer malfunctions it will always read 0. Then the car will surge the check engine light will flash and the speedometer starts working the car then runs smooth with no stalling. This can flip flop as often as every few miutes. The codes it is showing now are 21 and 43. I checked the ecm connections, clean and tight. Could this be a transmision speed sensor or an ecm? Oh! also when the speedometer is not working I cannot get any codes it will not even blink the 12 code. One time when I was checking the codes the light just stopped flashing in the middle of a code. Whatever it is it happened as I was checking the codes with just the key on? Sure enough, start the car and it was rough again.


I'm not proficient in pre odb-ii Regals. Maybe we can get someone like GTP Dad to take notice.

The problem is probably related to the TPS. According to my book the code 21 indicates a stuck or misadjusted TPS. This is probably why the car runs good sometime and then bad on others. The code 43 relates to spark control perhaps a bad knock sensor or connection. I would check the connection first as the knock sensor does not go bad very often. The speedometer issue is probably related to a bad transmission speed sensor. On these cars the speed sensor can cause other issues that can make your car run poorly. If you correct these three issues and you have other problems you may need to replace the ECM as it is probably developing problems.

Thank You for replying!! I could really use the help. Since I already had the TPS replaced I wonder if I should just go for the computer?? I can get it for less than $200.00

The problem is more than likely related to the VSS. If you want to replace the brain, you can buy one from Advanced-Kragen-Shucks-Checker auto parts for about $80.00 with a $100.00 core charge. Just take yours with you for exchange and you don't have to pay the core.

HotZ28 is probably right about the VSS needing replaced although I would make sure the throttle position sensor is properly adjusted, that is why you are getting the code for it. These have to be properly set when they are replaced.

HotZ28 is probably right about the VSS needing replaced although I would make sure the throttle position sensor is properly adjusted, that is why you are getting the code for it. These have to be properly set when they are replaced.


I agree with GTP Dad on the TPS. In the order of priority of DTC error codes this would be the first to tackle. Sounds like the PCM is going into limp home mode. The TPS in a 3800 Series I is similar to a Series II. There is a 5 volt reference signal from the PCM to the TPS. Based on throttle angle, the TPS sends a varying signal of approximately .4 volts at idle to over 4.0 volts at WOT. There should be at least 3 maybe 4 wires at the TPS connector. One is ground. If the TPS signals are correct, especially feeding back to the PCM, then the PCM is the next logical part to replace as both have suggested or it could be wiring which would have to be ohmed out. Good luck!

Hello Folks,
Thanks for the help I replaced the computer two days ago and so far so good no stalling it idles a little rough when it's cold but then runs OK. No codes logged yet and speedo works fine. I will run it a few more days then update you.