Rough Idle & Service Engine Light

[rsutoratosu]

So I was driving to work this AM, went two blocks and the engine started to make a rumbling sound. I pulled over and put it on park. So idle would go up and down. I shut the car off and turned it back on, still the same. So I drove it home and the service engine light came on.

Had to get to work so I just left the car and took the other car. I think I have a generic odbc reader somewhere, Ill need to pull the codes later.

Does this look like something I can fix ? Im itchy to know what the codes are. I googled a little and it seems it might be misfiring, bad coil ?

2007 Z4 3.0i @ 52k.

[Dine]

without the codes and without being there its very difficult to diagnose from the internet. It very well could be a misfire in which case you would want to look at plugs, plug wires, coil pack, injectors, etc (prob in that order). Bad gas could also be a culprit if you just recently filled up. Could be any number of things but pulling the codes will narrow it down to a manageable list. Good Luck!

[Finnegan]

^WHS

Coils are a pretty common failure. Codes are really the only way to narrow it down as in addition to the above there's the MAF, camshaft position sensor, etc.

BMW uses an extended code set beyond generic OBDII, so you may need a reader/tool that can read those. (In other words, if a generic read doesn't narrow it down, you may need a more capable tool.)

[rsutoratosu]

ok.. busy day yesterday, hopefully ill get home in time to find my reader..

[ANUSTART]

Mine rumbled and gave me the CEL last Spring after it sat for a while. Turned it off, let it sit, went back the next day and fired right up with no rumble or light. However, sounds like all the signs of a coil on the fritz.

[Dine]

Originally Posted by ANUSTART

Mine rumbled and gave me the CEL last Spring after it sat for a while. Turned it off, let it sit, went back the next day and fired right up with no rumble or light. However, sounds like all the signs of a coil on the fritz.

yours sounds like old gas or ethanol accumulating and burning off

[rsutoratosu]

P0302 code only.. misfire; spark plug; coil; etc.

I already got spark plugs like 2 years ago and never put them in.. I guess I can try that and go up the chain to coil if I need to.. Anything else ?

[jra]

Bad O2 sensor?

[Dine]

Originally Posted by rsutoratosu

P0302 code only.. misfire; spark plug; coil; etc.

I already got spark plugs like 2 years ago and never put them in.. I guess I can try that and go up the chain to coil if I need to.. Anything else ?

Any indication of which cylinder? I would start with the plugs and if that didn't fix it i would get a little 15dollar kit from your auto parts store that will check for spark in each cylinder (if you can't tell which cylinder is misfiring you could also use this kit to narrow that down from the start). you can test it with a number of combinations to narrow down if its the coil or the plug wire. If neither of those then you want to look at injectors and fuel stuff but i think most likely your problem lies somewhere in the first 3 tests.

let us know!

[StickMon]

Originally Posted by Dine

Any indication of which cylinder? ...

Many Google hits seem to suggest that the "2" in P0302 means cylinder #2.
Not a sure thing, but good one to start with.

That's why I bought a Peake Research scanner.
Have the GT1, too, but the Peake Research fits nicely in the trunk.

[rsutoratosu]

Yeah I google around, it seemed like 2 means #2. I been busy at work so I'll see if I can get to it this weekend..

this scanner was loaner from friend, I should give it back after 5 years now.. hahha

[StickMon]

Was looking for something else and ran across this from Ron Stygar over on Bimmerfest.

If it turns out you need coils, I bought these off Amazon back in May.
Price went up $8 a piece since.

Put them in about 3 weeks ago. So far so good.

[ANUSTART]

Originally Posted by Dine

yours sounds like old gas or ethanol accumulating and burning off

Certainly possible. It's been fine for about a year now.

[brock5ga]

Originally Posted by rsutoratosu

P0302 code only.. misfire; spark plug; coil; etc.

I already got spark plugs like 2 years ago and never put them in.. I guess I can try that and go up the chain to coil if I need to.. Anything else ?

P0302 is Cyl#2. If you have the plugs, go ahead and install them. Swap Cyl#2 ignition coil with another coil and note its position. Clear the codes. If the misfire moves to the cylinder with the ignition coil that was previously on Cyl#2, replace the coil. If the problem returns on Cyl#2, you have another issue.

[rsutoratosu]

Yeah I probably need coils... its freezing outside and todays project is storm door and floors.. I don't think ill get to this for another week or so.. I might as well order a few coils as they look to be pretty cheap, good to have spares for the future.

[rsutoratosu]

Replaced the coil. In the short time I ran the car, it seems fine. The service engine light doesn't automatically go away right ?

[StickMon]

I take it your scan tool won't reset it?
I've done it before with a generic scanner.
There should also be a way to do it from the instrument panel buttons, but searching is only turning up how to use them to reset the oil and service intervals.

[DerekSelmanRacing]

Actually, if you've cured the problem, I BELIEVE the service light will go off automatically after a certain # of starts and/or time.