Rough idle, detected misfires-- diagnosis?

[CrookedMile]

I've had my e36 sidelined for over a year because I can't figure out what's wrong with it.

When I turn the car on, it idles very rough, the engine appears out of balance, and the scans have revealed misfire on at least two cylinders. However, when I floor it, it starts to go away; the higher the RPMs, the less noticeable it is. :buttrock When I pull up to a light or idle in any way, though, I get the same original problem. I haven't been able to pass any smog tests because the scanners are detecting misfires on idle.

I've addressed this problem in a variety of ways and have heard a different answer each time. I can't afford to bring it to a shop, and I don't really trust auto mechanics.

I've heard to change the ignition coils, change the spark plugs, and even change or clean the EGR valve (though I've also heard that BMWs don't use an EGR system).

Can someone who has had direct experience with this exact problem please help me identify what's going on? I'd rather not waste my time and yours thinking about what it "could be". :help

[1wrangler]

In a completely dark garage (EDIT A dark garage DOES NOT mean an unventilated garage. It means all of the lights off. ALWAYS use proper ventilation when running a vehicle in a garage. The follow troubleshooting procedure would be completed very effectivly during the dark hours of the day, with the garage door fully open.END EDIT) with the engine running, look VERY closely around the ignition coil areas for arcing/sparks. Look underneath the coils where the spark plug boot goes into the head, checking for any signs of arcing. This is a coil-over-plug ignition system, correct? While looking for these arcs, you may need to get your eyes close to the coils before you start to see them. When you're in a completely dark garage, get your eyes near the coils, place a towel over your head to keep out any remaining outside light (be careful not to get it caught in the fan/belt!) and give your eyes a moment to adjust to the dark - be patient and see if you can find anything. Good luck!

[slocar]

In a completely dark garage with the engine running, look VERY closely around the ignition coil areas for arcing/sparks. Look underneath the coils where the spark plug boot goes into the head, checking for any signs of arcing. This is a coil-over-plug ignition system, correct? While looking for these arcs, you may need to get your eyes very close to the coils before you start to see them. When you're in a completely dark garage, get your eyes close to the coils, place a towel over your head to keep out any remaining outside light (be careful not to get it caught in the fan/belt!) and give your eyes a moment to adjust to the dark - be patient and see if you can find anything. Good luck!

Please don't do this ... the only thing worse than a car with a misfire is a car with a misfire with it's dead owner next to it. Carbon monoxide poisoning is no joke; and it can happen much quicker than you think. If you want to poke around and check for arcing, do it outside in complete darkness.


For a start, I'd go to your local auto parts store and have them scan the car for codes ... even if you don't have a check engine light illuminated, these cars store codes if something is wrong: that might give you a starting point ... and give us more insight into what to suggest.

But really, any misfire is either something wrong with the coil/spark plug or the injector ... there really isn't much else to it. If there was something wrong with the MAF, ECU or whatever else, it would show up on all cylinders.

[CrookedMile]

I knew this guy was trying to get a few laughs and telling me to do something insanely stupid... but thanks for the heads up. But seriously, what if I really were some misinformed idiot who didn't realize what this guy was telling me to do? If you're gonna crack a joke, make sure it's actually funny.

Can one of the admins please ban that guy from this forum for life? He just suggested that I monoxide myself to death in a garage. Probably not someone you want representing your community...

[Curtis328]

I knew this guy was trying to get a few laughs and telling me to do something insanely stupid... but thanks for the heads up. But seriously, what if I really were some misinformed idiot who didn't realize what this guy was telling me to do? If you're gonna crack a joke, make sure it's actually funny.

Can one of the admins please ban that guy from this forum for life? He just suggested that I monoxide myself to death in a garage. Probably not someone you want representing your community...

Umm... you should probably relax. I don't think he was cracking a joke. His advice was legitimate. I have a huge highway tractor shop that I work on my cars in. Carbon monoxide is hardly an issue with the ventilation system running.

I think he figured you aren't a complete idiot, and would take precautions to vent the exhaust to the outside if you're in a more confined space.

Chill bud...

[CrookedMile]

Okay, I'm sorry about that. Forget what I said about the ban. Thanks for the legitimate advice... I'll probably try that outside in the night time. Garage is probably a bad idea though, because of the carbon monoxide.

But what's the deal with the EGR valve? Do e36 328's even have them?

[radicalr6]

Do you have compression in the cylinders?

[CrookedMile]

Do you have compression in the cylinders?

For now, let's go with yes. My dad and I worked on it a while back, but from what I remember, yes.

[hyperchargedvol]

Have you checked to see if your valve cover gasket is bad? Resulting in letting the spark plug holes fill with oil and causing the mis fire?

[skeo]

What 1wrangler said is a common test to check for spark, just make sure you are in a well ventilated area and know what you are doing (i.e. you are playing with tens of thousands of volts and make sure you are not the easiest path to ground) before doing it! ;)

That said, I think the first thing you should do is have your engine codes read, they should tell you what cylinders you are misfiring on and any other problems that may or may not be related.

Misfires can be caused by a number of things, so it'd best to check the easy things first! I.E. hyperchargedvol said to check the headgasket for leaks. This is easy since you can easily see if there is oil around the spark plugs when you take the coil pack off. The headgasket issue is common on e36's.

I have had a rough idle issue myself, but mine was caused by my O2 sensor hooked up backward when they were replaced. When you have your engine codes scanned, ask the person to read the O2 sensor voltages for abnormalities, they should be switching above and below 0.5V constantly and rapidly.

Ensuring you have good spark plugs is also a good idea :). But the first thing to do is have trouble codes read, it's hard to proceed without that unless you know your car really well...

[1wrangler]

I knew this guy was trying to get a few laughs and telling me to do something insanely stupid... but thanks for the heads up. But seriously, what if I really were some misinformed idiot who didn't realize what this guy was telling me to do? If you're gonna crack a joke, make sure it's actually funny.

Can one of the admins please ban that guy from this forum for life? He just suggested that I monoxide myself to death in a garage. Probably not someone you want representing your community...


If you're not smart enough to either (a) run an exhaust hose from your tailpipe to outside or (b) LEAVE THE FREAKIN GARAGE DOOR AT LEAST HALF WAY UP then your probably not handy enough to fix this on your own anyways. Where in my post did I say to close the garage door while running the engine? A completely dark garage means NO LIGHTS, not no ventilation. And then you want me banned for life because I forgot to remind you about the dangers of carbon monoxide while working in a garage? I understand why this needed to be clarified- as a reminder - after I forgot it in my post but take it easy man, and have a little common sense! I appreciate those on here who clarified this for me so that those without any common sense that could have seen that and thought I meant doors closed instead of just lights off didn't harm themselves. CrookedMile - I just noticed your post about forgetting what you said about the ban. I appreciate that, and appologize for any confusion. Believe me, the very last thing I want is anyone to get hurt or worse from my advice. Suggesting working in an unventilated garage with the engine running was not my intention in the least bit. Good luck with the car, let us know what you find.

[hyperchargedvol]

That is what is wrong with the world today..no common sense!