DASC/ Idle problem.
 

Ok, after running through almost every possible scenario and reading a hefty amount of search threads. I must create yet a new idle/prob thread and call upon the forced induction pro's.

I just bought this 95' M42 supercharged ti. within 1 day of owning it and vrooming around testing the waters, BOOM! I have idle probs.

Myself, and the seller went through every hose and connection. We ruled out vacc. leak. We then took apart the PRV and cleaned that. took the spark plugs out and cleaned those. we took the IRV out and spayed it for gunk. tightened every hose and calmp. clean the ICV/IRV.

He even pulled out the volt meter and tested the barn door and pins on the AFM. We thought about testing the TPS but ruled that it prob wasnt the case. Im baffled. He's baffled.....

We concluded that it may be (electrical)relay related? Is this possible? Or that I might have a bad ICV/IRV.

I got home and read a (peak)code 1d.(Idle control valve). Before I go and blow 170$ can anyone provide insight on this issue.

SYMPTOMS:
Dies upon cold start
only idles rough when stopped
rough irratic idle
muffled idle

It actually runs like a champ on the highway or street. the problem is only at dead stop idle or cold start.

Thanks for the input!

sounds a lot like a ripped intake boot, but it sounds like you checked it from your post

First two things that come to mind, and I know you said you ruled out vacuume leak, but did you or the previous owner try spraying brake cleaner on the intake boot? I'm talking about the boot just behind the AFM. This boot often cracks and the tears are not always visable. Spraying brake cleaner on it while the engine is running will cause the idle to fluctuate if there is a leak.

The other thing I'd look into would be the CCV. It's a black disc located on the driver's side of the engine compartment with a little slit on the bottom. Sometimes this valve gets clogged up and starts to hiss. If you could hear it hissing at idle, it's probably bad. There's no way that I know of to check it without destroying it though. The plastic is usually so brittle that it falls apart in your hand when you take it apart. And finally, another thing that can cause your symptoms would be a clogged crank case vent. Not the actual valve that I was just describing, I'm talking about the hole towards the back of the valve cover where the hose connects. Sometimes this hole gets clogged with gunk and causes your crank case to overpressurize. Here's a pic of your engine bay:

Hey Jess,

you know I guess I could just go ahead and buy a ccv/prv valve. Its only like 50$ or so. It was quite gunked up and connects to rectangle metal valve, right? This connects to a hose with a T that we checked and double checked.

We did notice a lilttle bit of oil coming form the crank case but nothing alarming.(like, oh theres your problem). pretty normal eh? And it does hisss around that area, I just thought it was the bypass valve at norm.

Could be? I highly doubt it's the boot. He took everything off from the throttle body down to the filter.

How do you reccomend that I clean cc vent?

PS. I love what you named this pic! :tongue: thanks for the diagram, saved.

Oh I forgot to mention, all of these suggestions are fantastic! The code reader did however read a 1d - ICV. And I was not able to clear the code after multiple attemps of trying.

I'll double check the fuel vac lines again tomorrow. And spray some brake cleaner on the boot just for precuation, which we did not do.

Thanks again Jess. Maybe on my day off next week I'll cruise by and show you this car. Maybe grab one of those bombass burritos by your house.

IIRC, the ICV can be cleaned. I'm not sure, but I seem to remember that you should be able to blow into it and make it open/close. I could be mistaken though, it's been a long time. You could try spraying some brake cleaner in it to de-gunk-ify it, maybe check the wires and connector while you're at it.

As for the CCV, well I wouldn't just start throwing parts at it just yet. I've seen the vent hole on the valve cover get so gunked up that airflow was almost completely blocked. You can disconnect the hose and look inside the hole with a mirror and flashlight. I wouldn't try to break any of the gunk off while the valve cover is installed though, all of the gunk will fall into the head. I usually recommend that people clean this hole when they're replacing a valve cover gasket.

If you think the CCV valve is hissing, try putting your finger underneath it over the slit. If you hear the hissing change in tone, then you know it's clogged.

When you're spraying brake cleaner on and around the boot, try to spray underneathe it as well. Sometimes the cracks are at the bottom. Hose down the adjacent hoses as well. Any air leak aft of the AFM will cause a misfire or a strange idle. Also when you're spraying the brake cleaner, be sure to listen carefuly for idle fluctuations. If you hear it rev, go back and spray that area again.

The ICV actually did get cleaned, sprayed with brake cleaner. maybe the door is not functioning properly.

Thus reading the code.

hmmmmmmm, might I add that the seller is extremely knowledgable and knows the vehicle in and out, which is why Im thankful he was willing to look at it and help with the prob.

He even tested the lengthened electrical connections to see if there was current running in all 5 wires. Almost every angle was looked at. Im scratching my head.....

I think replacement parts are surely needed.

waaaaait, are you talking about the ICV or the AFM. If I'm not mistaken, the Idle Control Valve only has 3 wires and the Air Flow Meter has the door. If your code is for the ICV, check the ICV:wink:


Part#7 in this diagram:
http://www.realoem.com/bmw/showparts...13&fg=15&hl=21

yeah, thats the one.

it has a little hole/door however you reffer to ...ie: valve.

when I said wires I meant the all the elec. wires associated with the re/wire for the dasc. sorry.

Have you tried disconnecting the afm/maf and leaving the car running and see if that fixes the problem . i had a rough idle for months, i replaced the sparkplugs , airfilter , idle control valve with no improvement , someone suggested unplugging the mass airflow sensor and warming the car up which i did and found that it was a faulty maf .
i replaced mine with one from the scrapyard for £30 and now the problem is solved .

Bad O2 sensor can cause this. My car pretty much always did this due to the high level of boost and timing, so I'm not sure you'll ever cure it 100%.

Ok, Iv'e got an AFM on the way and I replaced the ICV and the CCV. And every hose that breaths air.

still radical idol & dying on cold start.........Im pissed. The only reason the ICV code was thrown was due to severed wire(s) from the ICV plug. The issue was hidden by the rubber boot, then this thing came completly detached at the prongs when I took the ICV out.

A $9.85 fix with a $170 bonus part. YESSSSS!

Anyway Codes cleared & the problem still persist's with no cel or thrown codes. I'll try the o2. thanks pnosker.

BTW, I have a considerable amount of hissing coming from the bypass valve area. Is this normal with the dasc?

it should hiss at idle, but under load when the valve is closed, there shouldn't be any hissing. It basically makes the boosted air go back into the inlet stream so the supercharger expends the least energy possible while under vacuum.

Thank you for the feedback.

I think I have found my air leak....

I've Isolated it down to the bypass elbow where it bolts up to the SC manifold back by the blower.

I've unnecessarily replaced all good parts, I hope this is it. But hey, you live and learn.

I cant seem to find a gasket made for this connection. Does one exist? Or do I make my own gasket?

Thanks
Guys