Intermitant Idle problem

[coolbear1]

My 93 325i won't idle. Just shuts of when you take your foot off the gas. It happened to my wife the other day, but by the time I got to it it had cleared up and was running fine. I pulled the fault codes and had 3, 5, 4, 20, and 1F. all of which are injector codes. 2 thru 6 to be exact. I cleared the codes and the car was fine for a week, then it did it again to me this time. I pulled the codes again and this time got a code 10, crankshaft possition sensor. I have had toreplace the crank sensor 3 times in two years. Seems odd to me since I have had the car since new and the origenal part lasted 270,000 miles.
Anyone have any ideas? I am going to clean and inspect the idle control valve next, which is, literally, a pain in the back.

[coolbear1]

Not the idle control valve, or the throttle position sensor. Both checked good, and in good condition.

What else?

Fuel related?

Maybe I will check the fuel pressure at the fuel rail next.
It runs if I keep my foot on the gas.

[coolbear1]

I removed the fuel, replaced with new fuel and tested the fuel pressure at the fuel rail. Fuel pressure good.
Had some improvement.

Idled for about 2 min.



No one out there?

[Mainthing]

Hey Coolbear1, did you resolve your issue? I saw you checked your IAC but take real close look at all you vacuum lines connected to the IAC and manifold. I found my problem was a cracked hose and actually this is the second time for me so I am replacing everything. Good luck!

[coolbear1]

Thank You, and no I have not resolved it as yet, and you know, you are exactly correct, that would be an easy thing to overlook, and I did not mention it.
To answer your question, that is the first thing I looked for.
But, the way I do it, and I hope someone will tell me that it is wrong,and I have missed something, is as follows:

1. I remove the air filter housing, and MAFF sensor.
2. I disconnect the two hoses that connect to the bottom of the rubber intake elbow, and remove the elbow from the throttle body.
3. I inspect the Rubber elbow for cracks.
4. I then plug the hoses that I removed from the Intake elbow (one is the idle air control valve intake, the other is the crankcase vent, they are all interconnected and open to each other when the car is not running, as far as I can tell).
5. I remove the vacuum line from the fuel pressure regulator,and pressurize the entire intake manifold with 10 PSI of air.
6. I spray around the hoses and manifold with a mixture of liquid soap and water to look for any leaks.

The pressure does seem to go all through the crankcase and intake manifold, but am I missing something.

This is not something I read anywhere, It has worked for me in the past. I think the theory at least in my mind, comes from my airconditioning/refrigeration background, looking for leaks I mean. But, this is not a refrigeration system, I may be missing something in this procedure.

[Jat007]

One other cheap part you should considering checking is your oil filler cap. These BMWs are designed and such that you escaped any pressure, the engine will surge.

Try to get a new oil filler cap and let us know.

[coolbear1]

Thanks, I will look at it in the morning, I think I have another one.

[Jat007]

My 325i was doing the same thing and I went and changed all sort of parts and still acting the same way. One day I ran into this great BMW mechanic that looking to do some side jobs - Well, long story short, he replaced the oil filler cap with his spare used, but better than the one I had on there and wholla the problem has been solved.

I recently bough a brand new oil filler cap on Pelican as my new spare.

Best of luck!!

[coolbear1]

I have access to several cars I car swap "known to be good, easy to change, parts" such as oil caps,around for diagnostics.

That wasn't it, but it sure could have been, I over looked it, and I thank you for your suggestion.

This forum would not work without people like you, and mainthing, and manolito sharing thoughts and experiences.

Thank you again for taking the time to try to help.

I have been too lazy to remove the intake monifold to gain access to the guts of the intake/ vacuum, idle, components that are down there where my big paws won't fit. I have been working by sense of feel, and I know better. I could have a cracked manifold, or something that cannot be found without removing the manifold.

And it is not hard, I just don't remember putting it on my list of "things I want to do for Christmas"!!!

By the way, Merry Christmas from The Coolbear, Mammabear and Grandbabybear, to any and all.

[coolbear1]

Well I have removed the intake manifold.
I looked everything over, looking for cracks in the manifold, idle control valve hoses, vacuum hoses, unpluged plugs, I tested the air intake temp sensor, and the coolant temp sensor with my ohm meter and the values were around 3 ohms at 60 deg. F on both sensors. That is right on according to Bentley. I am replacing all hose clamps, gaskets, injector seals with new. New vacuum lines, and crankcase vent hose also.

While I have the fuel rail out, what about bench cleaning injectors? anyone have a good procedure?

[coolbear1]

I put it all back together and I can certify 100% leak free everything as far as intake air vacuum and crankcase vent.
Still won't idle correctly. Odd thing is I am getting the same crankshaft position sensor code and it has a brand new one.
I am starting to suspect the ECM, or Idle control valve, or related wiring including the wiring between the crank sensor and ECM. I may also look a Ox sensor.
I am working much harder than I want, any ideas? any at all.

[97Green328Conv]

Hi Coolbear1! I have an idle problem on my 328ic. I got a Mass Air Sensor code and and O2 sensor code. It will stay running as long as I idle the engine high, but cuts off when I slow down or come to a stop. I am replacing the O2 sensor tonight, as it is the least expensive of the two. It is fairly easy to replace as well. Will let you know if it fixes the problem. I am worried it might be a vaccuum issue and may use your method to test if the O2 and Mass Air Flow sensor do not solve the problem. I have already tried to clean the Mass Air Flow meter with a can of cleaner, but no luck. Any other suggestions from anyone???

[coolbear1]

Look VERY closely at the rubber elbow, for cracks. Check the connections to the idle air control valve and crankcase vent on the bottom also.
One thing to keep in mind is, when you have fault codes on more than one component all of a sudden, it is usually a result of the components operating outside of normal operating range.
A symptom rather than a fault, and usually due to a related problem that is acting upon them.
Before I buy anything, I would look for , cracked or loose intake hoses, Dirty idle control valve, and injector air leak. The thrrottle body may be dirty, or it may be as simple as a leaking oil fill cap.
BMWs don't like air leaks on the intake downstream of the MAFF.
NONE!! tight as pos.

Good luck, I am still fighting mine. I have already done more than I wan't to.
Some improvement. Still no right.

[coolbear1]

Couple of observations, the car did great after I put the intake manifold back on and took it for a road trip. Idled fine at stop lights, and when I pushed the clutch in at speed, Until I pulled up into my drive. I seems to go into a coma after it reaches running temperature. It also seems to do better with the A/c on. The ECM seems to raise the idle speed when the A/C is on (makes sence).
Another note, the idle rpm drops and sometimes the engine shuts off when the brakes are applied at slow speed. I don't know if the vacuum assist is leaking internally, or if whatever is wrong just cannot cope with the vacuum fluctuation. I am going to try removing the vacuum hose from the brake cylinder and placing my finger over it to see if it makes any difference. tommorow.

[Jeron]

Have you tried testing the PCV?

When you remove the oil filler with the car running how does it behave?

With the car running and the oil cap off, test the suction a the filler hole. You can use a piece of paper or ziplock freezer bag or just feel the amount of suction on the filler cap when removing it. I am not sure I can describe the amount of suction but if it is too great then the PCV is probably bad.

[coolbear1]

Jeron,

Good to to here from you, I was hoping you would respond I need your help, this has really got me puzzled.

Hope you had a good holiday.

Question, where is the PCV? I thought many times about replacing it, but according to Haynes, an M50 engine does not use a "conventional PCV valve arrangement", and I cant find a part, or a replacement part listed by anyone, for anything, that would replace its function.
It is only a check valve isn't it? Can't even find one of those in the system.
I do remember a square screen type thing on the inside of the valve cover on the other side of the vent outlet. Could it have something to do with it? I ask because I replaced the valve cover with a used one, about a year ago, due to a crack in the original one. Could this be somehow related to my problem?

I will however try your oil filler trick. Also, I can't tell alot of change in the car when I remove the oil cap.

Also a question Jeron, If It was a problem arising from the crankcase, (be it too much vacuum or an air leak at the engine), if removed the crankcase vent hose at the valve cover and put my thumb over it, or otherwise close it off, would the engine smooth out? It is really only for crankcase gasses to return to the intake to be burnt, (emission control), is it not? I doesn't effect engine performance otherwise does it?

[coolbear1]

Jeron,

I did a forum search on PCV valve.

In a thread you refered to something called a "cyclone seperator" as another term for a PCV valve. Could you please elaborate. I can't find anything on my car that even remotely resembles a PVC valve as I know it.


I did however discover that I have no residual fuel pressure for some reason. The pressure drops to 0 in seconds. The Bentley manual calls for a minimum of 1/2 bar (about 7 psi) pressure drop after the pump has been idle 20 min.

The symptoms of this condition discribe my idle problem. I just need to find out if my fuel pump has a bad check valve, if the fuel pressure regulator is not closing, or if my injectors are not closing.

[coolbear1]

I removed the intake manifold again, and tested the ICV again, (it tested good the first time, hence, intermitant problem) and this time the OHM's tested , 10 OHM's across terminals 1 and 2, 9 OHM's across 2 and three, and 11 OHM's from 1 to 3.
Should be 20, 20, and 40, respectively.

Replaced the ICV, (idle control valve).

The car runs, and idles, like a tired, old BMW again!
I guess I will have to keep it to see if I can get 1/2 Million miles.

Didn't get much help from cyborspace. I felt a little let down this time.

[pete bogman]

Sorry you spent more time on this than you wanted and feel let down, but your posting will doubtlessly help many others track down similar problems, so thanks for your post and to those that responded with tips. This forum is a goldmine.

[coolbear1]

Your point is well taken, and was the reason for my follow through with information. I very much appreciate the site, and the people who help, I just wish more would. Any comment gets people thinking, and often leads to the answer to the problem.

Thanks