Reply With QuoteIf it was not already solved I would say it might be worn intake manifold gaskets or vacuum hoses causing a vacuum leak.
2 Grand Master
Okay, I had a crack at it today. I checked the intake rubber boots, no visible cracks there. I opened the maf on the bottom and cleaned the carbon wipe with carb cleaner and tissues. I adjusted the air idle mixture about 1/2 - 3/4 of a turn in (but I didn't put the car on a exhaust gas analyser like Bill R mentioned), which means I'm richening the fuel mixture. I guess the car is better now, well I warmed it up and took it for a spin and the problem wasn't apparent. The problem seems if I jab the accelerator really quickly when the car is stationary the car still stutters a bit, the same problem as I mentioned in the original post but now not nearly as bad. I clean the idle control valve with carb cleaner also, that I do about 5 months ago. My idle is really improved now, no "hunting" idle issues at all.
Looking through old posts I found a member with a similar problem here;
http://www.bimmernut.com/forum/showt...ght=afm+tuning
And found these useful websites on the matter, well afm realted anyway;
http://mysite.verizon.net/vzerdcib/e34a/id6.html
http://paulaxford.com/bmw730i/afm_service.htm
http://forums.roadfly.com/forums/bmw...3147035-1.html
Last edited by BigKriss; 12-08-2008 at 11:55 PM.
If it was not already solved I would say it might be worn intake manifold gaskets or vacuum hoses causing a vacuum leak.
1993 (build 93/05) 525i automatic M50TU (vanos) 263K miles (ca. 423000 km) in Montreal, Canada (bought the car 9 years ago in San Diego, CA)
2 Grand Master
I changed the headgasket just over one year ago and these items were replaced then.
Originally Posted by alex 1993 525i auto
Major Contributor
How new is your CPS?
2 Grand Master
It's never been replaced. I will take it out today (or try to) and test the impedance with a multimeter.
Grand Master
Sounds good...
I think a bit of the stumble is due to the nature of the AFM. I recall my car doing this before I swapped out the AFM for the MAF. (The MAF swapout created a whole new set of problems). My thinking is that when you stab the throttle, you have a momentary lean condition until the change in airflow can pull open the spring on the barn door and get the fuel to respond. It was never a problem while driving, only when lightly blipping the throttle - always would stumble. If you have something more than that, then that's obviously a problem.
A down and dirty way to check your A/F ratio is to drive the car and watch the MPG gauge. If the gauge surges back and forth on about 1/2 second cyles, the mixture is off relative to 14.7:1. You are seeing the injector cycling as the ECU attempts to correct the mixture. No surge means that the mixture is reporting back to the ECU as being correct and there is no need to adjust the ratio. Only works in closed loop mode (you go open loop when you depress the pedal more than about 2/3 of the way down or IIR when you exceed about 5k RPM).
Cause of this could be a bunch of things - old O2 sensor, vacuum leaks, out of tune, etc. Mess with your AFM spring and watch yourself really mess up the mixture.
Bellevue WA
90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
86 Porsche 951 - Track Toy
3 Grand Master
FWIW kriss my car never likes a blip of the throttle(never has) from idle,but its fine from an engine speed just above idle.....the second blip is fine but the first always bogs slightly then revs...
Last edited by Paul in NZ; 12-09-2008 at 07:28 PM.
Gone but not forgotten
Major Contributor
No need to take it out. Pull the connector off up by the fuel injector rail harness and test at the pins as per the Bentley manual. Maybe check the airgap between the sensor and the timing wheel as well. It needs to be pretty small (but not small enough to hit the wheel). HTH
2 Grand Master
, i'll get back to you soon Rus.
No need to take it out. Pull the connector off up by the fuel injector rail harness and test at the pins as per the Bentley manual. Maybe check the airgap between the sensor and the timing wheel as well. It needs to be pretty small (but not small enough to hit the wheel
Grand Master
1 mm is the CPS spacing. Use a feeler gauge to set.
Bellevue WA
90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
86 Porsche 951 - Track Toy
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