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Ron, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 36056
Experience:  34 years as a Tech
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2007 Pontiac 3800 series motor random misfire replace spark

Customer Question

2007 Pontiac 3800 series motor random misfire replace spark plugs wires and MAP sensor was still running really rough should I replace fuel injectors. What's my next step
Submitted: 1 year ago.
Category: Pontiac
Expert:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Before you replacing anything else, scan the computer system and see what the actual fault code and or codes are that should be setting, post back with them and we can work from there.

Customer: replied 1 year ago.
P0300 random misfire shows up. I also replaced MAF Sensor. Now I am hearing it might be loas of compression in a cylinder. I don't understand that as I was driving the car and it happened suddenly. Like one second perfect and the next bad..
Expert:  Ron replied 1 year ago.

The very most common cause for the code P0300 to set on this engine is usually a restricted catalytic converter. You can verify if that is the cases by loosing the exhaust at the manifolds till you have a healthy leak and then take it for a drive. If its restricted the power will return and the code should not reset. Try this before you replace anything.

Customer: replied 1 year ago.
I took catalytic converter off and the problem still existed I replaced coil packs problem still existed MAP sensor MAF sensor spark plugs and wires not sure if it might be the computer or even a-rod or roller kind of at my wits end
Expert:  Ron replied 1 year ago.

Have you also made sure there are no engine vacuum leaks? It would be a good idea as well to go ahead and run the compression test as well along with checking the fuel pressure while the problem is occuring. Check these things for me and we can work from there.

Customer: replied 1 year ago.
if I unplug all of the rear injectors, it makes no difference...Computer problems?
Expert:  Ron replied 1 year ago.

Maybe but first you need to see if you have injector pulse at that injector. You can check injector pulse with a standard 12 volt test light. Place the test end on the power side of the connector with the injecto plugged in and the ground end on the other wire and crank the engine over. If the computer is providing pulse the light will flash while cranking and running. Check this and let me know and we can work from there. Yo also need to make sure you have spark and compression on this cylinder as well.