Author Topic: Idle Problems (Read 5052 times)

melloh · « **on:** February 19, 2007, 08:56:38 PM »

Car: 91 318is
Non-stock item: DINAN chip (from ebay - possibly fake, but don't think it is)

I've had the car about 2-3 years now. In the past, had some cold idle issues, but minor (rough).

When I first purchased the car, I knew the first thing to do was replace all vacuum lines (e21 experience), so I went to realoem for P/Ns and ordered them all and replaced them all. This solved the symptom of the engine stalling on sharp left turns and smoothed the idle some.

Current Symptoms:
This happened on a long drive a month ago once - when gas released in neutral, would not idle and droped to a stall (little to no hesitation, like engine shut off). It "cured itself" after the car sat off for ~30 minutes. Did not reoccur until today.

On the way to school, same thing - would not idle and stallled imediately. On some restarts, would idle, but was high (~1500).

On the way home, again, would not idle.

Parked it at home, turned it off. ~ 5 minutes later, had my gloves on and searched for obvious vacuum leaks - none found. Started it up and it idled, but again was ~1500. After about 3 minutes, the idle began fluctuating from ~1500- 18/1900 in a very rhythmic manner. Looked like the computer was trying to compensate for something.

Also to test vacuum (not sure if this test works for the m42, but does for the m10), while idling, i removed the dipstick. There was absolutely no noticeable change. Was tempted to open the oil fill cap, but opted not to.

Other notes, not sure if related:

SRS light above center mirror is either flashing or on solid while driving

In picture:

Bolt @ A is COMPLETELY loose - as in I pulled it straight out w/o having to turn it. Tried to thread in by hand, but couldn't (might be because or resistance from rubber grommit). Oddly, NO signs of oil leak in this area or on that side of the head cover.

Bolt @ B has noticeable oil (fresh) around it and grim in that entire side indicates it has a slow leak and possibly other bolts on that side of the head cover. However, in doing oil changes myself, I have never noticed significant oil loss at all (maybe 1/4 - 1/3 quart per oil change @ ~4k miles w/ castrol 20w-50)

Thanks for your help in advance... any advice is very welcome!!

christophbmw · « **Reply #1 on:** February 19, 2007, 10:17:12 PM »

engine light on? check to see if any fuel injectors are leaking. you mentioned how it is a rythmic idle problem so it could be your ECU. did you start having the problems shortly after installing the dinan chip?

Tonyb · « **Reply #2 on:** February 19, 2007, 10:21:15 PM »

I had the same problem three different times, all three where spark problems. 1-Bad coil pack (had a crack in it) 2-bad plug wires (worn out) 3-Cracked ceramic on two spark plugs (1st Gen Bosch 4) Bad idle seems to be one of 3 things, Spark, vacuum leaks, or a bad AFM. Also check the fuel system (Pump, Dirty injectors, Filter)

melloh · « **Reply #3 on:** February 20, 2007, 02:08:17 AM »

Cool. I was first suspecting dirty AFM, so I plan on cleaning that out regardless. I'll see about the others asap. Is there a way to check wires? I suppose they haven't been changed, so I may as well change them anyway. I'm not sure where the coil pack is, hopefully the Bentley e36 manual will show me. (The e30 manual doesnt have the m42.)

Re: DINAN chip - no, it's been in there for about 2-3 years.

What about the fact that removing the dipstick didn't change anything? Does this imply vacuum leak? Should I try removing oil fill cap?

RED IS 91 · « **Reply #4 on:** February 20, 2007, 07:20:23 AM »

When I remove my dipstick there is no noticeable difference either.
Also on the check list is definately ICV ,CPS,and TPS.
Maybe it was my wife that said that about "MY DIPSTICK".

GOOD LUCK

maxwellredrum · « **Reply #5 on:** February 20, 2007, 12:03:44 PM »

also check the vac line to your fpr, unbeknownst to me i had been driving my car for months without the fpr hooked up and it didnt run poorly in the least, just extra fuel smell, when i found the line and hooked it up it smoothed out so much more and alot more low end power....magine that parts hooked up that are supposed to be;)

melloh · « **Reply #6 on:** February 20, 2007, 01:36:05 PM »

Ha ha... but hey, at least you have a dipstick. The poor new BMW owners have had theirs genetically removed....

Ok... so I just want to get these acronyms right:

FPR: Fuel Pressure Regulator
ICV: Idle Control Valve
CPS:

TPS:

Some sort of pressure sensor?

maxwellredrum · « **Reply #7 on:** February 20, 2007, 01:38:51 PM »

Throttle positioning sensor= TPS
Cam Positioning Sensor?= CPS

RED IS 91 · « **Reply #8 on:** February 20, 2007, 03:46:58 PM »

Quote from: maxwellredrum;19821

Throttle positioning sensor= TPS
Cam Positioning Sensor?= CPS

CPS= crank position sensor
I don't think that you can check resistance on your cam position sensor but your crank position sensor should be between 500-600 ohms.
good luck and keep us in the loop when you get it figured out .

melloh · « **Reply #9 on:** February 20, 2007, 03:53:36 PM »

Thanks fellas. It may be a while b4 I can get to this... working on 2 cars at once and midterms and class projects.

christophbmw · « **Reply #10 on:** February 20, 2007, 08:14:01 PM »

Quote from: Tonyb;19788

I had the same problem three different times, all three where spark problems. 1-Bad coil pack (had a crack in it) 2-bad plug wires (worn out) 3-Cracked ceramic on two spark plugs (1st Gen Bosch 4) Bad idle seems to be one of 3 things, Spark, vacuum leaks, or a bad AFM. Also check the fuel system (Pump, Dirty injectors, Filter)

make that four, a leaky injector can cause idle stumble when you let off the gas. it happened to me (but then it will throw an 02 sensor code.....usaually).

Tonyb · « **Reply #11 on:** February 21, 2007, 01:13:03 AM »

What makes a leaky injector? Bad O-ring?

mikesjo · « **Reply #12 on:** February 21, 2007, 03:35:15 AM »

New BMWs don't have a dipstick?! How do you check the oil level then?

maxwellredrum · « **Reply #13 on:** February 21, 2007, 06:06:49 AM »

heh heh heh.....the new mercedes dont have a drain plug for the O pan, mind boggling eh?
-Max

...p.s. im an ex-super lube tech

christophbmw · « **Reply #14 on:** February 21, 2007, 07:40:33 PM »

Quote from: Tonyb;19861

What makes a leaky injector? Bad O-ring?

no. when an injector gets an electronic pulse it sprays a mist of fuel (you probably already knew that). when it stops it is supposed to seal, if it doesnt then it will either drip, or spray fuel when its not supposed to, causing the excessive fuel to sit ontop of the valve untill the valve is opened again making the mixture too rich......a bad o-ring will cause an vacuum leak (although ive never seen this happen).