Sigh...Another Rough Idle Issue

[I-San-Juu]

So yesterday my 85 318i started running funny. I was driving and it started to kind of stutter. When i got to where I was going, it sounded funny. I did what I had to do, cranked it back up and it was idling real rough...I was still able to drive it. When I took off it would kind sputter, and it felt way underpowered(if thats possible). Im not an advanced enough mechanic but to me it seems like something is not firing as is should. It idles with no problem, I mean it doesnt kill. but it sounds like a very low popping. and instead of a steady flow of air coming out of the exhaust its choppy.

So I started checking stuff. I started with plugs and wires. If its running and I take a wire off the disty cap it will sound the same but way rougher, all on but one wire. The one thats at the top, like if you are looking at it like a diamond, its the one furthest away from the coil. When I took it off, the idle didnt change. So i'm like sweet...either that plug or wire is bad.

So I go and get some plugs(wires were out of stock) I get back and change all of them...Same thing...when I take off the wire and all. So now Im like it has to be the wire. So i go and get some wires, cap, and rotor. I get back change that, same thing...

When i try to drive it, it seems as if it completely stops running, and if I hold the gas down it eventually starts revving again. But hesitates real bad.

I tried checking the ICV and when I unplug it it revs high for a sec, and goes down and bounces a little.



Cliffnotes: rough idle, changed plugs, wires, cap, rotor. same issue. When I remove three wires(one at a time) the idle gets rougher. The other one when taken off the idle stays the same( is that supposed to happen?)

Anybody have any other suggestions? I searched and a lot of people say compression check, what do I have to get to do this? Or is it even something that I can do at home?

[MattsBMWs]

It sounds like a dead cylinder. Checking compression would be a good choice to rule things out. You just need a compression tester gauge. You should be able to pick one up on the cheap (or rent one). Just make sure it's the same thread pitch and diameter as your spark plugs. You should be able to find a how-to on the forums. Other thoughts, you could have a bad injector.

[brokenbimmer533]

My car is doing the same thing as you stated above. Checked for vacuum leaks, did the O2 sensor, injector cleaner and seafom. Finally took it in and I have little to no compression in cylinder 2. (< 10 psi) I wouldn't be suprised if this is your problem too.

[I-San-Juu]

Sweet. I think imma rent a gauge from autozone tomorrow. If that is the case, what are my options? Not including swaps. I mean how can it be fixed and is it worth fixing.

[brokenbimmer533]

Could be a wide range of things.
From what I have read it can be one or more of the following:
piston rings broken/cracked/ in other words just failed
blown head gasket (probably have milky colored oil)
intake or exhaust valve not seating right or bent
broken rocker arm
broken or weak valve spring
extremely worn camshaft

There are probably more but these are the main ones I think. Someone can correct me if Im wrong. This is just what I have researched on r3v. Leakdown test will help you pinpoint the problem.

As far as it being worth it to fix it, its up to you. After finals are over, I am going to get to work trying to locate the problem then determine whether or not the time/money/effort to fix it is worth the trouble. I will be swapping in an M50 come spring. (Ex. Tearing apart my engine to replace piston rings to get the M20 running correctly just to pull it out in 3 months doesn't seem to be worth it)This is not to say you shouldn't fix it though. I am running on 5 cylinders instead of 6 (decrease in power, decrease in mpg, amongst other things). Definitely not recommended. But if my M20 finally takes its last breath then I'll be biking to school and work. Not a big deal for me as I live a few blocks away.

Pinpoint the problem then go from there. Good luck.

Also compression testers can be had for relatively cheap. If you are interested in doing your own work on your cars, might just want to pick one up.

Ive said it once and I'll say it again, I'm no expert on engine repair or diagnosis. So corrent me if I'm wrong.

EDIT: Just saw I was in the M10 section. Above could still be correct though, not sure. Don't know much about the M10.

[I-San-Juu]

I dont plan on doing any swaps...I bought it for a daily so I dont have to put so many miles on my primary car, which was brand new with 15 miles when i got it in 06 and now has 84k miles on it...and since Feb, where i work i have to drive all day, so i end up putting well over 700 miles a week on, whatever I'm driving. Oh and it needs a tranny now :(

I havent had a chance to check it...its been raining too much..its supposed to chill for a couple days so ill try to get to it today.

[I-San-Juu]

Issue resloved...I feel dumb...

[Frog]

Issue resloved...I feel dumb...

well, do share...

[I-San-Juu]

stupid AFM was dirty

[Ramgoat]

so, you just sprayed carb cleaner and *BAMO*?

[I-San-Juu]

Yep...after nine months...LOL...

It idled rough for about 10 seconds, then smooth...took it for a spin, been good ever since...now, to find another window...

[I-San-Juu]

Can someone suggest to the OP in the attached thread on e30tech to do the same...

http://www.e30tech.com/forum/showthread.php?t=95700

[a3ternus]

so, you just sprayed carb cleaner and *BAMO*?

You re cleaning it by spraying into the MAF with the engine on?
I know stupid question,just wants to be sure!
N.

[I-San-Juu]

No, turn it off and take the intake apart and spray it directly on the part that looks like a little drop, you may have to open the flap to see it.

[a3ternus]

No, turn it off and take the intake apart and spray it directly on the part that looks like a little drop, you may have to open the flap to see it.

Thank you!
N.