Idle System Malfunction

[97 318ti]

Hi I was wondering if anyone had any advice with the following problems that I'm experiencing:
Recently my car has been experiencing difficulties in controling the idle speed of the engine. Normally my ti idles around 700-800 rpm but it idles at a much higher rpm, around 1000-1100 rpm and after cruising and returning to idle it fluctuates bouncing from 1000-1500 rpm.

I read the following codes:

P1140 - not sure what this one is

P0505 - Idle system malfunction

I'm not sure if this is linked to my throttle position sensor at all but I recently had the alternator replaced after it failed and have been experiencing problems with the car since. For instance the auxillary fan remained on long after the car was shut off and never shut off by itself. I removed the relay for the stage 2 and stage 1 auxiliary fan and after testing both for continuity and placing them back in the car, the fan seemed to operate normally. I'm confused and looking for some advice.

Thanks!

[bullmand]

Here's the other code:

P1140 Mass or Volume Air Flow Circuit Range/Performance Problem

Looks like it might be the airflow meter. They may have knocked something loose when they changed the alternator. I would check the wiring in that area and make sure the AFM looks OK.

[97 318ti]

Update:

So after a little diagnosing and ensuring that all the wires were correctly connected to the AFM I had a light bulb go off and decided to pull the gas pedal back to ensure that it was in the idle position and what do you know my idle speed dropped to its normal idle speed. The only problem is every time I press down and release the gas pedal, i have to pull the gas pedal back to reach the idle speed position.
My next steps are:
1) investigate the state of the spring in the gas pedal lever assembly (worn spring?)
2) check for slack in the idle cable (spring could be ok but slack could cause trouble?)
3) ensure that when gas pedal is released and cable slack is removed, that the throttle lever in the engine compartment is in the idle position

Does any one have any advice as to whether I'm on the right track or not?

[97 318ti]

oh yeah and thanks for the pointers bullmand!!

[Mallard]

check for any airleaks on the afm hose, this would give you a weird result.
loose jubilee clips also a possible.

[bullmand]

No problem. Good call on checking the throttle cable. It's entirely possible that it got kinked or bent or generally discombobulated during the alternator work.

[97 318ti]

No problem. Good call on checking the throttle cable. It's entirely possible that it got kinked or bent or generally discombobulated during the alternator work.

I did inspect the idle cable and didn't notice any bends in the cable that might prevent it from operating correctly so I took a look at the throttle lever where the throttle cable is connected in the engine compartment and noticed that the cable was very taut. When I pulled open the throttle lever, it would get stuck before returning to the idle position so I just loosened the cable adjusting it at the throttle body just enough to allow the throttle lever to return to idle and this seemed to fix the problem.

[Mallard]

then it sounds like the tps (throttle position switch)

nice and fast,...

lable all hoses, cables to TB (throttle body) and disconect.

clean out crud and oil in opening.

turn upside down, ther should be a small brownish square behind the hinge of the throttle paddle.

thats the TPS.

using the actuator (the clip where the throttle cable attaches) move slightly to the open position.

you should hear a click

depending on how well or badly the tps is set, the click should happen almost instantanious as soon as you move the lever. if its delayed then thats when you get hesitation..

if it doesnt click then you need to move the adjuster screw on th TPS backward until the click hapens at the point described before.

the screw will only require a miniscule amount of adjustment, so dont go crazy or you´ll end up doing it all over again :)

[Bam2002]

Hey I just had the Fan problem happend to me today at an Autocross. I ended up pulling the connection to the fan to shut it off. The fan would not shut off even with the car off and key out of the ignition. I even disconnected the sensor on the top of side of the radiator and it still was on.

So any Ideas? I see that you can pull the auxiliary fan relays and test them. So where are these located? I did a search and didnt see anythying on this.

Thanks..
Barry

[tastade]

The fan can probably run for a good ten minutes with the car off on a hot day. It keeps the engine from overheating, and it runs while it is off because the engine is still too hot and the heat will "soak" into components and damage them. If it never turns off it is probably a bad relay somewhere.

[Bam2002]

The engine was not that hot. It ran over the whole lunch break. At that point the air coming off the radiator was not even warm, and I could grab and hold the radiator hoses. So i think it was not that hot.

I just need to know where the relays are & wich ones to Test... I dont know where the Aux fuse box is. I found the one under the hood but it the fuse # was to the aux fuse box. Is that under the dash?

[tastade]

Maybe it is number 10 in this diagram, the temperature switch? This is for my M42, if you have a 1996+ with the M44 it might be different. Try unhooking the switch and see if your fan shuts off.

http://www.realoem.com/bmw/showparts.do?model=CG53&mospid=47505&btnr=17_0089&hg=17&fg=05

[pdxmotorhead]

Here's the other code:

P1140 Mass or Volume Air Flow Circuit Range/Performance Problem

Looks like it might be the airflow meter. They may have knocked something loose when they changed the alternator. I would check the wiring in that area and make sure the AFM looks OK.

The MAF to Throttle body hose on my car cracked in the bellows on the bottom side when I was doing some other maintenance, threw all kinds of error codes. Luckily the hose is less than 30 bucks and takes 5 minutes to change.... Caused a bunch of random activity drove me crazy for about a week....

Dave

[tarheel]

Hi 97 381ti from Atlanta and et al. I am having the exactly same problems you had back in early 2007 codes p1140 and p0505. What was the outcome of your work? Did you find the root causes? How did you solve it?