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-   -   325 Serious Idle problem, unique issue please help (http://forum.e46fanatics.com/showthread.php?t=956226)

BrokeBimmer 11-15-2012 08:46 PM

325 Serious Idle problem, unique issue please help
For starters I'm new to this forum. Typically a VW guy I have been ruthlessly attempting to repair my brothers 325ci. I've been researching the issue for weeks and have tried many things with no success. I will do my best to explain what's going on and what I have already done.

It is a progressive problem that began before last winter. I noticed from the passenger seat back than that when the car was at full running temperature and it was cold outside, the car was in nuetral or the clutch was engaged the idle would dip than surge back up. It was subtle back than and did not affect drivability. I recently replaced the alternator which failed, and in that time the temperature dropped outside. This winter it has not ran right since getting cold. Whatever was going bad has failed.

The idle now starts pulsing from about 400-1000 rpms very abruptly and will stall if you don't blip it. It'll smooth out after that but this happens at almost every clutch engagement in cold weather. I first thought maybe the alternator was bad so I replaced it again, checked the voltages at charging and battery, didn't have anything to do with it. The cold is the main factor. This only happens when the car begins to warm up, on an ice cold start the car idles fine. So no VANOS problems I believe.

Today my brother took it to school it was about 50 outside he said he couldn't get it to do it once. Than when he left at night, it was in the 30's he said it was doing it awfully. He is now scared of the car, if you clutch in while rolling it may stall.

So far I have taken the intake boots off and checked for leaks, cleaned the TB and ICV, checked the DSA. Checked the plugs, cleaned the MAF, replaced the belts. The thermostat was bad for wayy too long so I replaced that, as well as the FSU. That all funtions properly now.
THERE ARE NO CODES since i replaced the thermostat. It had a couple pending rich codes PO172, PO175 which never set the SES off probly because the car is flooding it with fuel to keep it from stalling.

It seems this is a very unique issue. I cannot find someone else with the cold being the main symptom at full running temperature. And that it is a progressive issue. The car is also leaking oil somewhere onto the trans around the fill hole. Im assuming its leaking from somewhere on top of the trans but I can't see that being a contributing factor.

The vehicle has only 109k miles. Any questions please ask, Im at my witts end. :ben:

shovelit 11-15-2012 09:06 PM

What about the oil seperator? I know BMW offers an "extreme cold weather" version. That's what I put on mine.
I did mine as preventative maintenance but I understand this can cause issues.

jfoj 11-15-2012 09:20 PM

Suggest you read the first link below in my signature.

Are you sure the engine is running rich or is the term that the deviation is too rich??

Many times the codes are a bit misleading.

Rarely do you actually have a rich code, the are almost always too lean.

What scan tool are you using?

What are the short and long term fuel trims?

BrokeBimmer 11-15-2012 09:22 PM

Thanks for the input. I may have to look into that although I wouldn't call NJ extreme cold conditions. The car was never overly well maintained, including oil changes. Could the oil seperator cause a warm idle issue when the oil is most thin, I run Castrol syntec 5w30 in her and it doesn't throw any lights when it's dying/stalling.

Its the expensive actron scanner from autozone that has values, i know still a POS. Ill check the fuel values/trim again tomorrow but they looked okay when I checked last. the Codes were PO172 and PO175. As far as I can tell there isn't a misfire, it runs great under throttle.
It's strange because I don't see many people throwing the rich trim codes as a common issue.

shovelit 11-15-2012 09:26 PM

I think by "extreme cold" they are refering to 40F. LOL.

BrokeBimmer 11-15-2012 09:31 PM

Hah, alright that and the CCV are next on the list as PM. Wish my brother wasn't a broke ass or I'd replace everything in the bay.
I'm also going to put the car on ramps tomorrow or saturday and see what the hell is leaking.

lucky_doggg7 11-15-2012 10:32 PM

I would look into replacing the PCV valve or rather test it to make sure it holds vacuum. Also, is there a small oil leak at the rear of the motor like a small drip or two? If so, here is the scenario I see: you step on the clutch, this moves the crank ever so slightly, but due to a weak rear main seal, and PCV valve not holding vacuum well, you now create a vacuum leak for the briefest of moments. This vacuum leak is not "monitored" air, so the idle dips, the ISV reacts to catch the dip to normalize the idle. As the PCV valve worsens and maybe along with the rear main seal also, but not necessarily, when the clutch is depressed, a bigger vacuum leak is introduced where the ISV can no longer compensate and the engine shuts off.

Next, it could be the ISV is wearing out. It's after all just an electro-mechanical part in a solenoid or electric motor of sorts so if it is getting weak in operation, it could be that it is not opening the valve enough in operation to make up for your "possible PCV" vacuum leak. Here is my caveat: Do not by any means take this info as being definitive and spend a bunch of money in swapping parts I mentioned. Do the research yourself and if it resonates with you, then act as you see fit. Good luck fellah.

BrokeBimmer 11-15-2012 11:14 PM

Thanks again for your input. It sounds like theres a hissing sound down under the intake stuff near the firewall, I'm assuming thats the PCV/CCV location. I'll do a tear down and check it out over the weekend. Also I was thinking it could have an RMS leak, although would that leak out onto the bell housing?
It's not a drop, the bottom of the trans where the drain plugs located is covered with oil. I will find out if this is trans fluid or engine oil.
The whole compartment under the engine area is dry.
Also a note that the maf, which I've checked was working correctly, was reading .38 lb/min
Is that low and could be a clue to an unmonitored vacuum leak?

shovelit 11-16-2012 04:49 PM

Definately chase that hissing noise.

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