1991 Pontiac Grand Am check engine light

Tiny
JARED575
  • MEMBER
  • 1991 PONTIAC GRAND AM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 90,000 MILES
Hi, my grand am, when I start the car "normally" the check engine light comes on and the engie idles really slowly and heavily, ie the car rumbles and can shake for a minute, after idling for a minute the engine speed will level off and sound more normal however when I go to press on the gas pedal and drive off the engine hesetates and drives like a tank, there is clearly no power and the engine will heat up very quickly but won't overheat. Now I had the engine tuned up at my local midas, "level 2 service" according to the bill which they said should fix it. It worked for a week. They said whent hey scanned the computer they were getting a "long cranking code error" now whe I took it back tehy rescanned and said it was the same error and it was most likely becasue the car was old. This was about 1 year ago, Now I recently learned that if I crank the engine for a minute but don't allow it to start, then wait for the lights and stuff to shut off and then recrank the engine it starts very quickly with no check engine light. Also if I am driving and the check engine light came on at startup that if I get to 60km/h I can pull a fuse, top eft I think it's labelled ECM, wait 5 seconds while costing the engine sounds like it stalls the speedometer drops to zero and the check engine light flickers, once I plug it back in the engine starts running and everyhting comes back on and the engine runs wonderfully. Now I was wondering what is causing this, it's a new starter, new spark plugs(not sure about the spark plug wires) but what I can't figure out is why it does this, is it the computer? I bought a a reader, I turn the car to on but don't start it and the check engine light blinks out the codes that are stored, I get code 42 all the time and once and a while code 33, right now that one isn't there jsut 42. Thanks for any help!
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Saturday, May 30th, 2009 AT 7:24 PM

3 Replies

Tiny
KHLOW2008
  • EXPERT
Hi jared575,

Thank you for the donation.

Is this a 2.3 L or 2.5 L engine?

There are various different specifications and the correct one is needed for accurate diagnosis.

Code 33 is the MAP sensor circuit.

Code 42 is for EST (Electronic spark Timing) circuit.

The VIN would help in determining the system used.
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Sunday, May 31st, 2009 AT 12:02 PM
Tiny
JARED575
  • MEMBER
The vin, which i'm assuming is the vehicle identification number is 1g2ne54u3mc510398 it's a 2.5L LE model 91 pontiac grand am.
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Sunday, May 31st, 2009 AT 11:31 PM
Tiny
KHLOW2008
  • EXPERT
Yes VIN is Vehicle Identification Number. You are able to provide the details so here are the description and diagnostic procedure.

CODE 42, EST CIRCUIT OPEN OR GROUNDED

Code 42 indicates the ECM has seen an open or short to ground in HEI EST or by-pass circuit.

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This test confirms Code 42 and determines if fault is a hard failure or intermittent condition.

2. This test checks for a normal EST ground path through the ignition module. If EST circuit is shorted to ground, reading will be less than 500 ohms.

3. As test light voltage touches by-pass circuit, the module should switch. This will cause the ohmmeter to switch from hundreds of ohms to thousands of ohms. This test assures that the module "switched".

4. If module did not switch, this step will test for a short in circuit No. 423, an open in circuit No. 424, and a faulty ignition module connection or module.

5. This step confirms that Code 42 is a faulty ECM and not an intermittent problem in circuits


http://www.2carpros.com/forum/automotive_pictures/192750_Code42EST91GrandAmLE_1.jpg



http://www.2carpros.com/forum/automotive_pictures/192750_Code42EST91GrandAmLE01_2.jpg



http://www.2carpros.com/forum/automotive_pictures/192750_Code42EST91GrandAmLE02_1.jpg

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Monday, June 1st, 2009 AT 9:13 AM

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