Question about 1991 Pontiac Firebird

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Obd1 codes it has rough idle and will not accelerate with dying. problem is interment. Most times you can turn the key off and start it back up and it runs fine. no codes triggered. Have replaced the dist., coil, icv, throttle ps, map sensor. please give me some idea! I about to think ecm.

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  • Pontiac Master
  • 1,250 Answers

Could be ignition module or a coil or crank sensor or cam sensor
hope it helps

Posted on Mar 27, 2014

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6 Suggested Answers

6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

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fixincars
  • 335 Answers

SOURCE: obd1 scan tool will notaccess

A couple of ways to check and see if the computer is ok first:
check engine light must come onwith they in on position
The fuel pump must run for two (2) seconds with the key ON
There must be a 5 volt reference at sensors like map, TPS
Must communicate with scan tool
The ORANGE wires at the computer are you power input wires one has 12V all the time this is your KEEP ALIVE MEMORY
one is 12 with the Key on you MUAT HAVE VOLTAGE AT BOTH
Check the computers Ground most are out under the hood and are brown wires
Try the GM TAP TEST this is a factory authorized test with the computer connected and you verified all of the above SLAP the computer with the open hand firmly not too hard but firm see if anything changes,
Do not disconnect the battery you will erase all the codes!
Please contact me if you need any additional information.
If you find the information provided helpful please give me a good rating
www.aceautomotive1.com

Posted on Aug 14, 2008

emissionwiz
  • 76846 Answers

SOURCE: 1995 pontiac bonneville 3800 v6

P0321 Spark Reference Circuit. The spark reference signal is used by the PCM to improve ignition timing accuracy during crank and at engine speeds of up to 1,200 RPM. The spark reference circuit allows the use of ignition control mode below 400 RPM, eliminating the need to utilize module mode during start-up, and also allows the PCM to calculate true crankshaft position in 1/6 the time that use of the fuel control reference signal would permit. During normal operation, the PCM uses the spark reference signal to control ignition timing until the engine speed exceeds 1200 RPM, at which time the fuel control reference signal is used. There is no connection to the TCS.
If everything checks ok then the PCM is defective PCM.

Posted on Aug 28, 2008

fixincars
  • 335 Answers

SOURCE: 1993 pontiac grand prix 3.1 liter

the 3.1 had some EGR problems, EGR valve stuck open, blown diaphrams, Plugged passages Im not saying that is all your problems and I believe yours has whats called a linear EGR about $350.00 from the dealer (and that is the only place you ever consider buying such a critical part for the emissions system regardless of the cost)
That car is so antiquated as far as computers go that relying on the codes is nearly pointless! Map code can set because of low engine vacuum which you will have with a poor running engine, Check for 5 volt reference voltage at the TPS and MAP with the key on and engine off if no 5 volt reference I suspect a Computer. Computer Ground is on the Thermostat housing and needs to be clean and secure.
There is a legit test in the GM factory manual called the TAP TEST take the ECM (computer) and slap it with an open hand, if the symptoms change the ECM is bad it's very common in the early-mid 90s for the computers to go bad in one way or another the circuit boards come loose and suffer also from cold solder joints.
Make sure the wires are on the correct plugs and hopefuly you used factory plugs and wires and No split fire or bosch plugs only AC delco
Make sure you have good spark on all 6 cylinders.
Contact me at fixincars@yahoo.com with the results and any feedback or questions

Posted on Sep 19, 2008

csmock132
  • 4669 Answers

SOURCE: po300 code, replaced 1 crank sensor needing to know voltage on se

Resistance check the coils. Check for spark on all 6 cylinders.

Posted on Apr 02, 2009

wyatt1582
  • 453 Answers

SOURCE: throttle/Idle/running problem - wants to run too fast, or stall out

RPM's up and down check EGR valve and sensor. EGR valve and sensor control idle. That's why your getting the surging on rpm's and this could be giving out the other codes. If mass flow was bad car will not start and the same for the map sensor. O2 sensor measures gas and air for right mixer. TPS controls 0-60 speed as in throttle respons.

Posted on Apr 28, 2009

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