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Discussion Starter · #1 ·
I am still getting random misfires on 6. Don't know what to try now im at a loss. So far i have replaced: Coil, spark plug, cleaned ICV, replaced valve boot, fuel filter, fuel pump, engine cover gasket.

So whats next? it seems like every time i replace a part the car runs well for a few days and then starts missing. Also sometimes the CEL comes on when the cylinder isn't missing.

Thanks guys!
 

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What comes to mind is the coil pack connector or the fine wires that run into the coil pack wire harness that runs over the top of the engine in the same compartment that holds the battery cable from one side of the engine to the other.
First I'd suspect the connector. I'd consider getting a new connector and splicing it into the bundle making the correct appropriate wire matches of course. Assuming this is within your skill set to do a professional job.

I'm not familiar with the parts back at the ignition control, so I don't know whether there are discreet components that are assigned to each coil pack. If so, one could go bad.
 

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Do you feel the misfire?

Cold start, under load?

Suggest a compression test and cylinder leakage test to rule out mechanical issues.

Could be a questionable injector, however, do not see these often. You could move the injector or pull all of them and send them to some place like www.witchhunter.com for cleaning.
 

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Discussion Starter · #4 ·
@stinger9. Good advice i didn't really think about that, I'll look into that after a compression test thats defiantly something some one else would have to do for me.

@jfoj. Yes you can feel the misfire the car feels shaky and you can hear the engine running rough and a huge loss of power.
It has only happend once on a cold start it is usually after the car is warm and im sitting at a light for a long amount of time.
Ill have to go get or borrow one of those then what should the compression be? and if my compression if off then does that mean its a cylinder gasket?
 

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With a helper to crank over your engine, a compression test is not hard.
DIY would pay for the cost/rental of the gauge.

Compression should be in a cluster around 175 lbs. as I recall. More important is how each compares to the rest of the cylinders.

Cause if compression test fail is valve seating, compression rings, or head gasket. Don't go here until you do the test!
 

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Since you now mention your problem is only on cold start, I would hold off on a a compression and cylinder leakage test for now/

I would look very closely at the SAP vacuum lines connecting to the bottom rear of the intake manifold. There are a number of vacuum connections right at the rear underside of the intake manifold and could easily cause cylinder #6 misfires.

Also you need to be aware than sometimes you have multiple vacuum leaks that become additive and may impact a single cylinder more than others.

You really need to read the first link below in my signature.

Suggest you pay careful attention to the SAP vacuum lines and I would highly recommend that you replace the DISA O-ring and verify that the DISA does not need to be replaced anyway.

I see you have a 2001 330, your car should have a vacuum controlled SAP valve, the later 2003-2004? 330 went to a different SAP system that did not use a vacuum control.

Again, think about when you have 2 different vacuum leaks, the first one possibly from the DISA O-ring that does not cause enough problem to trigger codes for other cylinders, but then you also have another leak near intake runner #6 and then you may end up with a single cylinder misfire.

Many of these cars are over 10 years old, all the rubber and gaskets are compressed, oil soaked and hard and they are leaking air and vacuum into the crankcase and intake path causing all sorts of issues.
 

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Yea, if you check realoem you can figure out when the 330 went to a non vacuum controlled SAP system, BUT, there is a MAF on the input of the SAP and if this thing goes bad $$$$. I am pretty sure the 2004 had the MAF based SAP, cannot recall if 2003 had it?

Not sure what is the better choice, the MAFless system is cheaper to maintain, but has more vacuum leak potential.
 

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$83 MAF > $3 Vacuum hose!
 
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