At my wits end Bad Idle M42

[1996 328ti]

I have not taken it off jack stands yet.
I've grown accustomed to seeing it sit that way.

What I don't get is that the car is fully assembled and ran for 10 minutes with no problem other than the knock control regulation fault now.

Could it have anything to do with a new gas filter?
I'm also going to look into cleaning the MAF and thanks!

Wish all you guys were closer.

[BimmerBum]

It almost sounds temperature related. I'm still leaning towards the cat. I bet as it gets hot the cat closes up causing idle issues.

Do you have gloves that would allow you to remove the O2 sensor from the exhaust when it is hot? I would run the car fully assembled until it starts to stumble for a little bit. Shut it off. Quickly unscrew the O2 sensor and start it again. See if it will idle.

When it is stumbling have you tried revving it? What does it sound like when you do that, sometimes you can tell buy sound that the exhaust is plugged up.

Clogged cats can do strange things. I spent a lot of time chasing down an intermittent cyl 2 misfire on my E46. Plugs, coils, fuel injectors... nothing. We figured out that it had to be the cat. Cyl 2 is has the shortest path to the cat so as the cat would close up it would back up cyl 2.

Originally Posted by 1996 328ti

I have not taken it off jack stands yet.
I've grown accustomed to seeing it sit that way.

What I don't get is that the car is fully assembled and ran for 10 minutes with no problem other than the knock control regulation fault now.

Could it have anything to do with a new gas filter?
I'm also going to look into cleaning the MAF and thanks!

Wish all you guys were closer.

[1996 328ti]

The stumble was very slight.
I can have the cat removed.
I'd be afraid to drive the car to the exhaust shop with the O2 sensor installed.

The last time I drove the car it did sound like an old diesel.

[BimmerBum]

Originally Posted by 1996 328ti

The stumble was very slight.
I can have the cat removed.
I'd be afraid to drive the car to the exhaust shop with the O2 sensor installed.

The last time I drove the car it did sound like an old diesel.

I would try what I suggested and go from there but my money is still on a clogged cat.

[1996 328ti]

With everything assembled, idle stumbled a few seconds at 3 minutes and again at 7 minutes. Ran for 15 total.

Went for a ride. Car sounds like a motorboat. Doesn't accelerate well.
I'm bringing it to an exhaust shop first thing in the morning.
Maybe he can take some pressure measurements.

I know it would have ran without the O2 sensor installed.

[BimmerBum]

Keep me posted. I'm always curious to see how good my over-the-internet-diagnosis ability is.

Originally Posted by 1996 328ti

With everything assembled, idle stumbled a few seconds at 3 minutes and again at 7 minutes. Ran for 15 total.

Went for a ride. Car sounds like a motorboat. Doesn't accelerate well.
I'm bringing it to an exhaust shop first thing in the morning.
Maybe he can take some pressure measurements.

I know it would have ran without the O2 sensor installed.

[1996 328ti]

Originally Posted by BimmerBum

Keep me posted. I'm always curious to see how good my over-the-internet-diagnosis ability is.

It cost me $40.
But no. It's not the cat.
I had it removed this morning. It was original anyway.

I'm leaning towards the MAF. A good forum member has one he can send me.

[BimmerBum]

Originally Posted by 1996 328ti

It cost me $40.
But no. It's not the cat.
I had it removed this morning. It was original anyway.

I'm leaning towards the MAF. A good forum member has one he can send me.

Damn. Try unplugging it and see what happens.

[1996 328ti]

Originally Posted by BimmerBum

Damn. Try unplugging it and see what happens.

The motor runs smoother. A little higher RPM but smoother.
I haven't actually driven the car that way.
I will on the way home from work today.

[BRADESTAR]

Yea, unplug that and give her a go. I'd bet it will be smoother and that'd give you an answer.

Could give it a good cleaning too whilst awaiting the other MAF.

Intake/vacuum sytstems on these things seem pretty finiky to me. Gotta be jest rite or who knows what codes it'll throw.

[1996 328ti]

I'm going to pick up cleaner today.
I saw some MAF cleaner.

K&N are the worst! I would never buy a care that had a K&N again.

[BRADESTAR]

Preaching to the choir there bud! Mine had a cone filter on it. My first order of business was putting it back to stock. Must have been a period of time where this type of thing was popular. I won't even sell the old, going in the bin to save somebody else the trouble.

I'm sure you'll report the result.

Still a decent read, this thread. I hadn't heard of clogged cat's and that is interesting. I'd think that the car would cut off if that was the case.....like the ole' "banana in the tailpipe".....

[pdxmotorhead]

The trap door style AFM works best with a regular air box that's for sure...
It prevents oscillation of the door.

Its pretty common for the wiper to wear out or just get gummed up..
The 95/m42 does get some reverse fog up to the meter contaminating the
assembly.. I clean mine about once a year..

[1996 328ti]

I remove the AFM and clean. I assume it's just where the air flows and I don't have to take unscrew the bottom? There may have been a marginal improvement but it's cool out. But still acceleration is poor.

Disconnect AFM and somewhat better but maybe because the idle is a little higher.
But still, the car doesn't have the pep it used to.

I do think it's temperature related but still stuck.

It's been suggested to clear the adaptation codes. How on an OBD-I?

[1996 328ti]

Next I disconnected the battery and shorted (+) to grounds for 10 minutes.
Drove again. Car seems to rev better but I think it's because it's in the 70s and not 90s.
Still have a 'Knock control regulation' fault.
And the car still sounds like a motor boat.