My E39 Stalls when warm

[SMOODY]

Our 2001 525iT has started pulling a new trick recently. Basically it does not like to stay started when you try and start the car after it only sits for an hour or so.

If the car sits overnight, then it starts just fine. But if the engine is still warm, it will stall when you step on the gas.

Any thoughts?

[M-technik-3]

Clean the HFM with rubbing alcohol. Mine was shot so I had to replace it. If you have a CAI style air filter IE K&N that you use oil on the filter the Oil sometimes gets ingested in the system and lands on the HFM. This causes it to give erronous signals, hence why California is going to no more CAI at the end of August.

It won't belong till the two other Communist States, Massachusetts and Virgina to adopt that rule. Heck even Mass has adopted no aftermarket exhausts, that they need to be OEM.... Funny as some auto manufacters don't make exhausts for their cars and let aftermarket take care of that. Proves they are trying to get anything off the road that's older than 10 years.

Yes I'm ranting but hope that fixes your problem.

[SMOODY]

I do not have a K&N filter in the wagon, just the standard paper filter.

I pulled the HFM out last night and cleaned it off, although it did not appear dirty. I also pulled the intake tube and cleaned the throttle body which was dirty. Hopefully that was the problem.

The last time the car stalled, the computer set the "service engine soon" light. I plan to order a OBD II tool so I can read the code(s) and reset the light.

We shall see what happens.

[OwnedbyDuncan]

If you have the radio code try this. Disconnect the the battery and leave the battery disconnected overnight. Reconnect in the morning and see if problem reoccurs. Also check for vacuum leaks or rotted hoses along the intake tract.

How old is the O2 sensor in the car? Has it been changed?

[SMOODY]

I do not think that I have the code for the radio. It may be in the paperwork for the car. I should probably track that down.

I checked for rotted hoses and vacuum leaks in the intake when I cleaned the HFM and throttle body, but I did not find anything that looked bad. My wife used the car yesterday to run some errands and did not have any issues starting the car, but power is still a little off. I think the computer may be running in a default mode.

The O2 senors are the original ones that came on the car. I inspected the lead wires and they looked fine. I did not check the resistance of the sensors. It is possible that they are drifting out of spec given that they are now 4 years old and have 40K+ miles on them.

I ordered the OBD II tool yesterday, it is on its way. Then I can get the ECU to reveal its secret.

[M-technik-3]

I would have said you can use my peake tool but it's only up to 96. The s52 I bought, I'm converting to obd I.

Hope this helps. O2 sensor going bad after only 40k is questionable but it's possible.

[SMOODY]

I ordered the Peake tool for the 2001+ cars. I figured that it was worth it given that I have 2 cars that I can use it on. It will pay for itself after only a couple of uses. Although I think it is a bit of a shame that you have to order a $150 tool just to get the fault codes out of the ECU. My Chrysler (like most of the OBD 1 equiped cars) flashes the check engine light in a pattern to show the codes. I guess the manufacturers want you to take it to the dealer so they can make more money, I mean fix it properly.

I agree that 40K is a little soon for an O2 sensor to go, they usually last more like 80K+ miles, but you never know.

[M-technik-3]

But with this tool you can reset the oil and the inspection lights.

[SMOODY]

But with this tool you can reset the oil and the inspection lights.

Being able to reset the "Service Engine Soon" light was another reason I did not mind spending the money for it. However, there is a procedure to reset the service interval lights on the newer BMWs (after mid 2000) without the tool. The steps below came from the my330i website.

"After Mid-2000: You only need to hold the left odometer reset button while turning the key to position 1 (Accessory). Keep holding the button for 5 or so seconds until any of the following shows in the on board computer display: OIL SERVICE or INSPECTION with RESET or RE. Release the button and press it again for another 5 or so seconds until RESET or RE flash. While the display flashes, press the button one more time briefly. If done correctly, END SIA should show up for a few seconds. All done. "

I have done it on both the e39 and the e46 successfully.

[SMOODY]

Well I have an update. I plugged the car into the Peake tool and it was told by the computer that it thinks there are problems with the Throttle Body Position Sensor and the intake cam postion sensor.

I then cleared the codes and started the car. After running for a while, the code for the throttle position sensor returned. The code for the cam sensor did not. The car has been running fine, and has not stalled since I cleaned the HFM.

I searched the internet over the weekend looking for more information on issues with the throttle position sensor, but I could not find anything pertaining to the engine in the car.

Any ideas? Should I break down and take it somewhere?

[Dirichlet]

Well I have an update. I plugged the car into the Peake tool and it was told by the computer that it thinks there are problems with the Throttle Body Position Sensor and the intake cam postion sensor.

Smoods - I had the same problem w/ my E46 - stalling, weak power, etc. This problem actually first turned up as I was driving to the autox school this spring. It was due to the intake cam position sensor. Essentially, your car is running in 'safe mode' when you feel that reduced power, and the stalling, I was told, was from the same thing. It's an easy fix - just a plug in sensor. I had mine done at BMW Towson while I was having a million other things fixed - but you may be able to do it yourself. Best of luck.
~Colin

[SMOODY]

Well the e39 decided to act up on my wife Thursday evening. She managed to get it home, but wanted the car fixed ASAP.

We took it to the dealer on Friday. They verified that the cam postion sensor was bad and replaced the $100 part along with $300~ labor. The car has behaved for the last couple of days, so hopefully it is fixed.

The dealer also tried to tell me that the engine computer was reporting a problem with the engine not coming up to temperature fast enough. They said the fix was a new thermostat housing for only $400. Because the car has been running fine when the engine is cold and I did not see any codes related to this with the Peake tool, I balked and told them to just do the cam sensor. I am sure that their $25,000 diagonostic computer can extract more details from the engine computer than my $150 tool, but I figured that I would see at least one code on the Peake tool that indicated an issue. They also said that their system did not register a problem with the throttle position sensor.

Is the code chart that came with my tool wrong?

Have you guys ever heard of a problem with the thermostat housings in the e39 or was the mechanic just worried about paying rent this month?