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RussMasterTech
RussMasterTech, ASE Certified Technician
Category: Car
Satisfied Customers: 791
Experience:  19 years of GM Dealership experience. ASE Master with L1 and GM Master Certified.
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1996 Pontiac Sunfire 2.4L. I have a code of p0300 multi-misfiring.

Customer Question

I have a 1996 Pontiac Sunfire 2.4L. I have a code of p0300 multi-misfiring. I have replaced the ignition module, ignition coils, coil tower, wires, plugs, crank sensor, knock sensor, pcm. When I replaced the ICM all four cylinder started to work for 1 minute and started to misfire again. The first misfiring was from cylinder 1 & 4. The second misfiring came from cylinder 2 & 3. Can you please advice me on to how to approach this issue. Thank You
Submitted: 8 years ago.
Category: Car
Expert:  RussMasterTech replied 8 years ago.

Hello.

When does your engine misfire?

Customer: replied 8 years ago.
It misfires as soon as I start the car. The check engine light flashes and the cooling fan comes on. The cataltic converter becomes red. I checked all the injectors and it shoots gas they all work correctly.
Expert:  RussMasterTech replied 8 years ago.

I had one of these cars with the 2.4 engine where the timing chain had jumped a tooth, or the chain had become so worn that the cams were no longer timed correctly. Since the miss is on all cylinders, you should try checking the cam timing marks to make sure they haven't jumped. I've also seen it where the oil pump pressure regulator valve sticks and the oil pressure goes sky-high. Sometimes it can go as high as 90 psi. This will do a couple of things. The oil filter may baloon up, and or the lifters will over pump and hold the valves open thus creating a misfire condition. You might be able to verify the timing chain condition with a compression test. The oil pump issue, you'll need to hook an oil pressure gage into the port where the oil pressure switch is located. This is by the power steering pump on the intake cam housing.

Good luck. Let me know how it turns out.

 

Thanks for using Just Answer.

Russ

RussMasterTech and 4 other Car Specialists are ready to help you
Customer: replied 8 years ago.
I took the ignition coil pack and module out of the spark plugs to see if I get sparks to each cyindar.(Like removing the spark plug wires from the plugs and holding it close to the ground and cranking the engine to see if I have a spark) but I set it on top of the engine and I saw 1 an 4 did not spark but 2 and 3 did spark and I have good compression on all cyindars. (I played with the crank pully and I haveno free movement, I don't think the timming chain is loose).
Expert:  RussMasterTech replied 8 years ago.

If one set of cylinders is not firing, then the coil that runs that cylinder or the module that runs the coil is at fault. It could also be the wiring harness between the module and the coils. I know I see that you've replace the coils and the module and the housing, but maybe try swapping the coils and see if the no spark condition stays on 1 and 4 or moves to 2 an 3.

 

Thanks for using Just Answer.

Russ

Customer: replied 8 years ago.
ok, I'll follow your advice I will get back to you tomorrow. (I was thinking it could be the wiring harness) Thanks
Expert:  RussMasterTech replied 8 years ago.

Let me know how it works out, but if I've been of any help already, please make sure to click the "Accept" button so I may receive credit for helping you. I'll be glad to help you in the future.

Thanks again,

Russ

Customer: replied 8 years ago.
Hi Russ, thank you for your help the car is now runming
Expert:  RussMasterTech replied 8 years ago.

That's great!!!

Glad I could help.

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