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GM Tech (Cam)
GM Tech (Cam), Auto Service Tech
Category: Car
Satisfied Customers: 29396
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have 2 cylinders not firing..spark plugs..ignition coils

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I have 2 cylinders not firing. I had it hooked up to a computer and the codes were P-0300: random misfire detected and P-0304 cylinder #4. I changed out the spark plugs, checked to see if the ignition coils were malfunctioning and they were fine. I am smelling some wires getting hot in the cab of the vehicle at the ECM. I inspected the wires and did'nt see any damage. The vehicle is running poorly, and the fuel economy is bad. No smoke coming from the exhaust. I think it is possibly the ignition control module but i don't know how to check it. Is there anything else that i can check to find the problem? The vehicle was running fine at the end of the day and the next morning is when i started to have the problem and the check engine light came on.
HiCustomer Thank you for asking your question on JustAnswer. The other Experts and I are working on your answer. By the way, it would help us to know:

-What year is your Car?
-What make and model is your Car?
-How many miles are on your Car?
-What type of engine is in your Car?
-What have you already tried?

Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Customer: replied 7 years ago.
What info do you need for you to help me?
When I replied, your vehicle information was not displayed. Also I feel there are experts more experienced with Isuzu so I will opt out and let them assist you.
Customer: replied 7 years ago.
The vehicle is a 1996 Isuzu Rodeo with a 3.2 liter motor, no distributor, fuel injected.
OK, while we wait, which cylinders are missing, you mentioned #4, is there another?
Customer: replied 7 years ago.
Yes i said #4 and #6. When i disconnect the ignition coil with those 2 cylinders there is no response as opposed to when i do the other four cylinders i get a response in the motor. After i had disconnected the ignition coils i had pulled the coil from each cylinder and hooked them back up and put a spark plug in each of them and was getting a spark from the plug. I feel that it is something electrical because i am smelling wires in the cab of the vehicle getting hot by the ECM. Which i pulled the ECM out and checked the wires for damage and did not find any damage. I also checked the board in the ECM for damage and nothing. My father said he had the same issue before and it was the ignition control module but i am not sure how to check to see if that is the problem.
OK. Let me do some research. As I mentioned I know little specifics about this model, but no one else has stepped in so I will see what I can find.
Customer: replied 7 years ago.
something else to ask. Does the ignition control module have anything to with the electrical with the fuel injectors. If the ignition control module will interfere with the injectors then i would feel better to change the ignition control module?
It does not seem to, it only appears to run the igntion coil. Did you try swapping the coils from 4 and 6 to other cylinders?
Customer: replied 7 years ago.
Yes, and i also have pulled the coil off and put a spark plug in the end of it and cranked the motor and was getting a spark in cylinder #4, but when i put in back together and start the vehicle i would unplug the ignition coil and get no response from the motor. But if i where to unplug the coil off cylinder #2 i would get a response
OK, so the coil is firing so this is no sounding like an ignition issue. Have you checked the mechanical of the engine? A compression test? Given these cylinders are side by side, it is possible you have bad head gasket.
Customer: replied 7 years ago.
No i havent done the compression test yet but i feel that it is something electrical due to the smell of the wires and the fact that when i came home at the end of the day the vehicle was running fine and the next morning it wasnt and that was when i started to smell the aroma of the wires.
OK, that is reasonable. Take the connectors off those injectors and test for power on the red/blue wire with the engine running. It should have 12v.
Customer: replied 7 years ago.
If that is good and the compression is good do you have any idea what else it could be?
OK, if there is power, and the compression is ok, and we are certain the spark plugs are firing, then we are looking at a faulty injector or the wiring between the PCM and the injectors 4 and 6 are bad.
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