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Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 12719
Experience:  32 years Foreign / Domestic Cars All aspects of Diag and Repair
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Olds alero: litre..2001 quad dohc misfire..cylinder..control module

Customer Question

2.4 litre olds alero 2001 quad dohc misfire on number three cylinder all the time, have replaced the plugs, boots, coil packs, the housing for the coil packs, and the control module that the coil packs plug into. any suggestions. The only other thing I can think off is a bad injector or maybe dropped valve the only other thing else i can think off is replace everything again
Submitted: 6 years ago.
Category: Car
Expert:  Randall C replied 6 years ago.
Hello, although replacing the parts mentioned can be a little tricky as you know, the odds of replacing all of the parts and still wind up with #3 misss would be rare. The computer controls 2 cylinders (1 coil) at a time so i am leaning against a computer control circuit problem as you would lose 2 cylinders. I realize due to the setup is is hard to check for spark but a trick you can try to see if it is a spark problem is...

remove the coil housing as one unit. Remove the rubber boots. get 4 spark plug wires ( many times they are sold seperate at parts store. You do not need any certain ones just 4 wires about 12" long. ) The wires will snap on the plugs as well as snap on the stems where the boots went.

lay the coil housing to the side and leave #3 wire unconnected but pluggred into an old plug. lay the plug/wire against something metal and run engine and see if it sparks. If it does, then you need to but a cheap compression guage and be sure you have say 150 psi in #3 cylinder. If so, then yes, suspect an injector is clogged

this is how we test this type of system in the shop. I hope it makes sense. You are simply linking the coil housing to plugs with 4 spark wires. I realize this is added expense to but the wires but this is only way to view for spark or not. You can always ask the parts store for cheap set of wires from a say.. 1996 chevy cavalier? they will work
Customer: replied 6 years ago.

Well I guess I will try this. Well if I am getting spark for sure, but say no compression this means rerring job or new motor or rebuilt right or possibly new head from a dropped valve right which would be leaking. Well cannot get compression gage till tommorrow but will check make sure I have spark today if I can get the wires possible close( i thought of doing it that way but was not for sure on that) hard living out in country. The way you explained the coil packs makes alot of sense definately for sure. I will definately get back to you and let you no what I get compression wise you said 150PSI So gonna try that. Well if i got good compression and spark look at injector or could that still be a valve possibly. After a little further inspection i have noticed some coolant on the back side of engine but looks like it may have came from the plastic piece inline from the return on the heater core ( it better be that if not I might have found my problem also there). Now I know why I became a master plumber instead of a mechanic lol. Will get back 2 you for sure on this and let you know what I come up with. any more suggestions would be greatly appreciated..thanks for helping will get back to you as soon as I find out about everything.

Expert:  Randall C replied 6 years ago.
Sory for dealy. I cant make more suggestions just yet without being armed with all the info. I will say rings are rare. You would be looking at valve or headgasket problem if low-no compression. LMK as soon as you can. thanks

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