2002 saturn vue cylinder 1,3,5 misfiring when replaced coil pack, it went away now cyl 4,6 misfiring and idling low at 500 rpm. Replaced coil pack and it is still misfiring. Checked timimg, compression test, no vacumm leaks, replaced plugs, O2 sensor, camshaft sensors, cleaned fuel injectors. Vehicle runs great when driving and gives NO codes. Gives codes PO 304, 306 only at idling.
Having PO 304 = Misfire cylinder 4,PO 306 = Misfire cylinder 6, as I read above you have done the most. The thing that you have missed is to check whether the Catalytic Converter is faulty or not. To get an idea check whether you have a smell like rotten eggs at the end of the exhaust,you start having problems with cat and needs replacement. My advice before you go for a cat replacement is good to visit an MOT center and check your emissions and then you decide,
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SOURCE: 2003 saturn vue came in
You need to forget what you have already done...This is going to just mess with you. Pretend that you have never seen this vehicle before and start over with the codes. I gater from your description that you are dealing with a 3.0L Dual Overhead Cam V6.
I also gather that you are getting codes P0301, P0302, and P0305.
If I am "gathering" correctly, this places your problem on all the cylinders on the rear head. Check all your plugs and make sure they are gapped properly. Check to make sure that your injector connectors are plugged in. (You did say you had the heads off) Check to make sure that your coil connectors are plugged in. If you are sure that everything is plugged in properly, test coil pulse at each coil connector with a test light. Test for injector pulse at each injector. I have seen some of the Saturns with a separate connector for the rear-head coils and injectors. If this one is equipped with that, make sure it is plugged in properly. If this does not turn up the problem, retest your compression on the rear head. If the compression looks OK, go ahed anyway and recheck the valve timing. You could be one tooth off on the rear head and it won't be bad enough to affect compression during a cranking compression test, but enough to cause misfires with the engine running.
Don't fall into the trap of "I already replaced this" or "I know I did this right - no need to recheck". I have seen thousands of dollars worth of parts replaced unnecessarily due to this. CHECK EVERYTHING AGAIN! Like I said at the beginning of this, the best way to handle a problem like this is to pretend you are trying to figure this out for the first time. The only thing you know is that "someone" had the heads off. Other than that, you don't know anything.
If none of this turns up a suspect, post a comment to let me know.
SOURCE: Vehicle running rough initial code misfire cyl 2
May be fuel injector on Number two cylinder, normally if it's the mass air flow it would affect all cylinders. You may have a sticking EGR valve or a PUrge canister valve stuck open, if you need to know how to check this let me know and I will give you more instructions. I also need to know if it's the 4 or 6 cylinder engine and if it has a automatic or standard shift I need this to help diagnose the problem more. The other codes is for the 02 sensor but you need to check the other stuff first before you mess with the 02 sensor. Thanks for using fixya
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Thank you so much for replying. I will definitely give that a shot and get back to you. Thanks again.
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