2003 325i misfire cylinder 5

Hello, first post but have searched this issue relentlessly. I have not been able to find any thread where the OP or another poster has tried everything without result. I get a cylinder 5 misfire on first start of the day only that clears itself up after 5-10 seconds. I have done the whole ccv system, vanos seals, moved coil and boot, brand new spark plugs, and moved the injector. Every time the problem has stayed with 5. I have even checked the vacuum plugs on the back of the manifold. My stft are right around 0 so I don't think a vacuum leak is my issue anyway. I am out of ideas except for the DME. Any insight would be greatly appreciated.

My disa flapper is in good operating condition and I have put new intake boots on as well

ttt

Seems like this is a common problem. One member had the same issue and found success by fixing a broken DISA flap. The specific member is on page 3 of this thread > http://www.e46fanatics.com/forum/sho...=185001&page=3

Did miss any mention of fuel injectors?

I assume you have a code, P0305, for the misfire.

A misfire is defined as, the expected work has not been performed. Depending on the speed, throttle position, and other similar such variables, the crank has to get from one position to the next within a certain period of time. A misfire means that the time frame was exceeded, the crank did not make it from here to there as expected.

You have done the basic diagnostics of moving the coil and boot to a new cylinder, and the problem remained on #5. This means that either the spark plug itself is the problem, or the fuel delivery to #5 is deficient. The other work that you did should play into a more global problem (multiple misfires, reports of lean, and so on), so it is logical to me that after making these kinds of repairs you would still have a problem with a unique cylinder.

Your next diagnostic step should be to swap the #5 fuel injector. One of the problems with this is that disturbing the position of the injector(s) should cause a ripple affect by upsetting the sealing qualities of the o-ring seals.

My bad, I see that you swapped the injectors already.

^exactly, he's already done a lot of what I would have recommended. I think searching around for similar case solutions is probably your best bet OP

Well this morning I unplugged my disa before initial start up and there was no misfire or shaky idle. No codes except for the disa circuit. So maybe my disa diaphragm leaks but I thought I had tested that properly. Tomorrow I will plug the disa back in and see if it misfires again. If so disa is the issue even though I can't see how it would cause only a cylinder 5 misfire.

It definitely is weird to me too. The only thing I can think of is the air to fuel ratio is being affected enough by your disa to throw a code.

Second morning in a row without misfire with disa unplugged. Will try with it plugged back in tomorrow and post results.

Ok, after work I plugged in the disa and the misfire is back so it looks that it is the culprit of my cylinder 5 misfire on cold start up. I will do one more start without disa plugged in tomorrow morning but it looks certain. Thanks for the replies.

Suggest you check the first link below in my signature, it will most likely have the info you need.

Likely the DISA O-ring and/or the DISA vacuum actuator diaphragm is blown.

It is odd that the disa would only affect 5, but maybe that's when the car runs out of air after 1-4 have gulped down what they need?

O-ring is not a bad idea as well as checking the function of the valve (seeing it's firm and not wobbly).

I'd also make sure your air filter is clean too. And, by the same token that disa might be involved because of air distribution, I'd still check lines for leaks...specifically the sap vac line, if you have one.

GL!

In followed the disa checks in the misfire thread and thought the diaphragm checked OK and I put a new o ring on as well. My sap has no vacuum lines but I did check the plugs on the manifold. The disa valve is also tight and wasn't flopping around. It definitely confuses me how the disa only affects cylinder 5 but that's what is happening.

Originally Posted by dmax

It is odd that the disa would only affect 5, but maybe that's when the car runs out of air after 1-4 have gulped down what they need?

O-ring is not a bad idea as well as checking the function of the valve (seeing it's firm and not wobbly).

I'd also make sure your air filter is clean too. And, by the same token that disa might be involved because of air distribution, I'd still check lines for leaks...specifically the sap vac line, if you have one.

GL!

What? The misfire on 5 is because the car runs out of air after 1 thru 4 sucks it all down?

That makes no sense, especially when actually considers the Firing Order of 1-5-3-6-2-4.

JD...sorry, I was just theorizing...maybe it's coz all the air was sucked in after one cylinder? I didn't know the firing sequence, but as 5 seems a consistent issue, and OP has seen an improvement with disa unplugged, I was trying to figure out why that would be.

Well misfire tonight when I got home from work with the disa disconnected so I am back to stumped. I swear sometimes I hear a popping noise when it starts up while the rpms are jumping around but my ccv is brand new.

Another thing I don't understand is that my short term fuel trims are close to zero which says that there is no vacuum leak.

How long have you had the car? If it's a relatively new car to you, then I'd check out the cooling system to see if it'd been replaced shortly(ish) before you got it...check date on the ET label. I'm thinking (out loud) that maybe you have a small crack in your cylinder head that's feeding into 5 only.

You might notice a very small loss of coolant. Perhaps you would notice the lack of a quiet hiss when you open up ET...indicating the system is losing pressure somewhere. You may or may not notice contamination of either oil or coolant. Just putting it out there to consider.

You've covered everything, it seems, but injector wiring...not sure how to test that, but I know you could somehow. The only other guess I have is that something you think is fine (like plugs being tight), really isn't. Nothing personal.

Have you done a compression test?

Maybe cylinder 5 has a mechanical issue, rings or valve train that causes the initial misfire.