1999 Pontiac Grand Am Mis-firing

Tiny
WDILLS
  • MEMBER
  • 1999 PONTIAC GRAND AM
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Car is running on 2 cylinders. I removed the assembly of the coils and ignition module and turned it upside down. Installed normal wires from the this assembly down to the plugs. Started the car and used a timing light to determine that the first and last cylinders are not firing and that the car is running on the 2 center cylinders. Used an ohm meter to determine that both cylinders that are not firing were going to the same coil. Assumed the coil was bad and replaced it. No help. Swapped the location of the 2 coils and still the same cylinders don't fire. Installed a new ignition module, still the same problem. I have checked the wiring harness that conects the ingnition module to the coils with an ohm meter, it seems OK, all circuits read about 0.2 ohms. I checked the resistance of the individual plug circuits inside that white plastic cover that the coils mount in. Each read about 1.2 ohms. I am at a loss.
Sunday, February 21st, 2010 AT 2:21 PM

8 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hi, thanks for the donation. Did you check the coil grounds, one ground for each coil, one is white, the other is orange, that's how the computer controls the coils.
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Sunday, February 21st, 2010 AT 2:49 PM
Tiny
WDILLS
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The wiring harness from the ignition module to the coils has 3 wires. A brown that goes to both coils and 2 whites, one going to each coil. All 3 read ok when checked with an ohm meter.
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Sunday, February 21st, 2010 AT 6:27 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
The white and orange wires at the top of ignition module. There has to be a pulse, You can take connector loose at both ends, pcm and ignition module, then check continuity. You may need to check for codes, at the least, you need an obd11 code reader.


https://www.2carpros.com/forum/automotive_pictures/170934_grand_am_SE_1.jpg

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Monday, February 22nd, 2010 AT 12:41 PM
Tiny
WDILLS
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I'll check the white & orange wires for a pulse. Problem should be on pin A which controls cylinders 1 & 4 because they are the 2 that don't fire. What type of pulse should I be looking for? Is it 5V, 10V? What is that pulse referenced to, ground or another pin? Can I read it with a volt meter or do I need an O-scope?

Thanks
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-1
Monday, February 22nd, 2010 AT 1:48 PM
Tiny
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  • 5 POSTS
Hooked up a OBDII code reader, got the following:
P0113
IAT sensor 1 circuit high input

No idea what that means

P0342
Camshaft position sensor A bank 1 circuit low input

Sounds promising

P1336
ignition system misfire

Obviously

Hope this helps.
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Tuesday, February 23rd, 2010 AT 9:34 AM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hi, you have the 2.4? Use a spark tester on plug wire that isn't firing. Then, can take the connector loose from pcm, use a testlite connected to battery voltage, key on, probe the terminal for the white wire, if the tester sparks, everything from the test point to plug should be ok.

The P1336 says the pcm needs crankshaft variation relearn procedure.

P0342 is cam sensor counter, not incrementing. Your getting to the point, I'd have to look at it.
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Tuesday, February 23rd, 2010 AT 9:40 AM
Tiny
WDILLS
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The problem is solved. I spoke with a local mechanic and he told me the resistance check I did on the white plastic housing / cover that the coils mount in was useless. Even though they read as a good circuit when measured with an ohm meter, they can still not work. Based on his advice I bought a replacement, installed it and the car runs fine.
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Wednesday, February 24th, 2010 AT 7:19 AM
Tiny
JDL
  • MECHANIC
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Glad you got it going your way.
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Wednesday, February 24th, 2010 AT 9:06 AM

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