91 Buick Regal Computer Problem ???

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Hello my name is Ken I am a newbie to this forum so I will apoligize in advance if I post something wrong. I have a 91 buick regal with a 3.8 FI w/auto a/c etc. it has 210,000 miles on it and until tonight no real trouble. Tonight however on the way home from work the car started to studder like it was misfireing. I noticed that the speedometer was below 0 (I have analog gauges), and the check engine light was blinking at no set seqence. The check engine light has been on steady for some time now but always goes off when I decelerate and comes back on when I accelerate. The last two things I noticed was as I approched my exit on the highway and let off the gas the check engine light went out as usual and the car ran fine for about 2 more minutes. Then as i accelerate from the red light it started missing again until I got home. In the driveway of my house I put the car in park and the engine would rev to about 2000 RPM. I shut the engine off and then turned the ignition on and off five times in a row hoping to rest the computer no luck. I then left the ignition on (without starting) and watched the check engine light blink what seemed to be random blinks. I started the engine and again it idled at about 2000 RPM's. I have no clue. Any help would be appreciated.

posted by  bean329

Turning the ignition key on and off 5 times will not reset a General Motors ECM

Make sure the cahrging system is working properly and the battery is holding a charge

Before clearing codes, I think it would be a good idea to know what the ECM is telling you. It isn't hard. I've done it as an shade tree car hobbiest on a 1990 Skylark I used to own and on a 1990 Buick Century which is still in the family.

There will be a 12 pin ALDL (diagnostic connector) somewhere under the driver side dash. The upper right two pins can be connected with a bent paper clip or a jumper wire. With Key ON, Engine OFF, after pins A & B are connected, look at the check engine light. It will blink 12 three times (One flash - pause-two flashes) The it will spit out two digit trouble codes, repeating each I think three times before going on to the next code. When code 12 flashes again, the computer has given you the trouble codes.

Once we know the codes, We may be able to tell you more about troubleshooting the car and identifying the problem before you go buy a bunch of parts. This may require a digital multimeter, or some other simple tools depending on the trouble codes

I would find the codes and attempt to resolve the issues identified by the ECM prior to clearing them - to clear the codes, lift the negative terminal from the battery for a minute or two and reconnect it. If you have anti-theft (Delco loc II ) radios, tape decks, etc., there are some certain precautions you need to follow to concerning the activation codes you need to follow

Regardless of the troble codes you find, go ahead and make sure wiring connections are good - especially to the ECM, ignition module, coil packs (I think the GM 3800 has DIS) the crankshaft position sensors and the cam shaft position sensors.

If you don't feel comfortable working around this stuff, you can get some repair manual information from AutoZone.com or from a Haynes manual (can be bought @ most autoparts places for around $15.) Even if we are able to help you, it would be a good investment if you are going to attempt to trouble shoot this car.

Get back with us when you know the trouble codes and we will try to help

posted by  tbaxleyjr

the light blinks to fast for me to count. the blinking seems totaly random. now the car misses and rev's to a steady 2000 rpm ???

posted by  bean329

with engine off, key on, (al the way to on without engaging the starter) and A&B terminals jumpered, the blinking should be slow enough to count. If it is still too fast to count, a good shop with an ASE certified tech or a dealer service department may end up being a good alternative.

Without knowing the diagnostic codes, all anyone would be doing is making uneducated guesses. A good diagnosis is the process of eliminating one cause at a time - still making guesses but in a more educated manner.

posted by  tbaxleyjr

ok i let the car set for a while and i can now read the codes, there are serveral. i managed to get the car to a friends shop were they had a fancy scanner and my codes matched there codes. 13,15,16,21,22,23,26,27.
he suggested doing a major tuneup since i have not done it for a long time. Replaced plugs, wires, PCV, clean battery terminals and replace air filter.i am going to replace the fuel filter tomorrow. He also suggested moving the electrical wires around in the engine compartment to see if i have broken connection or shorted wire, all moving of wires turned out negative. Now the car sometimes runs ok mainly after setting a spell and then again one time after driving about 4 to 5 minutes.

posted by  bean329

Sounds like a vacuum leak, all but the part about the check engine light going nuts with the engine off and ignition on. It would be worth your time to check for leaks.

posted by  DodgeRida67

13-Oxygen sensor voltage stays between 0.35 and 0.55 volts for 30 seconds when the TPS signal was above 0.55 volts. The engine had been running for at least 40 seconds with an engine temperature above 110° F.

15-Coolant temperature sensor signal indicates a temperature colder than -36° F for at least 4 seconds after the engine had been running for 2 seconds.

16-Charging system voltage was either below 9 volts or above 17 volts for 10 seconds.

21-TPS voltage was above 0.8 volts for 5 seconds when engine was running and air flow was less than 15 gm/sec, or the TPS voltage was over 4.8 volts at any time.

22-TPS voltage was under 0.2 volts for 4 seconds when the ignition was on.

23-Inlet air temperature sensor signal showed an air temperature of -29° F for 4 seconds.

26-Qeruad-Driv sense voltage shows a low voltage when battery voltage should be present, or if the sense voltage shows battery voltage when a low voltage should be present for at least 5 seconds when the engine was running.


btw if a car shows more than 3 different diagnostic trouble codes it usally is a bad computer

you really need to take your car to a good technician and have him check the sensors out with a lab scope it defenatly isnt a do it yourself kind of job unless you really know what you are doing :thumbs:

posted by  chevyluv

I agree with chevyluv on this one = There is either a bad electrical ground @ the ECU, low voltage @ the ECU powersupply feed or a bad ECU. Chevyluv said it well about further diagnosis is a job for a dealer service department or a good repair shop. To troubleshoot this number of sensor errors requires knowledge of what the sensors are doing (i.e. the voltage levels, pulse widths, etc), when the sensors/devices are supposed to be doing it (the ECU's operation logic/programming) and a good wiring diagram for the car.

posted by  tbaxleyjr

the car is in the shop of a friend. I will let you know what happens.

posted by  bean329

With all the sh#t codes your collecting, I would make a trip to one of the many junk-yards, that you have and purchase a used ECU, before I would pay for 2-3-4 hours diognostics + parts. :2cents: I've been wrong many, many times :oops:

posted by  lectroid

how much does a used ECM run in a junk yard? May have to re-use the memcal or prom chip from the old ECM

I know a "remanuafcutred" ECM runs about $100 @ autozone but has to re-use the memcal or prom chip from the old ECM

May be worth a shot since labor @ a shop is $65+/hr nowdays.

posted by  tbaxleyjr

I thought about the problem all weekend, I am willing to try an ECM and a $100.00 is not a problem. Thanks for confirming my thoughts. I will let you know how it goes.

posted by  bean329

ECM ECM ECM ECM did I say ECM. he also changed the TPS and the coolant temp sensor. Picked it up yesterday drove a bit today seems to be ok. Thanks for advice.

posted by  bean329

Thank you for letting us know what the results finally were.

posted by  tbaxleyjr

no problem

posted by  bean329

I forgot this was here. Used ECM, usually around $50.

posted by  lectroid

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