Re: Loss of Power while running

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Posted by Walt Barie on January 29, 1999 at 13:06:14:

In Reply to: Loss of Power while running posted by Chandler Ogden on January 27, 1999 at 22:28:56:

Could indeed be fuel system related. I had a similiar problem and it was the fuel pump relay (part of the combo relay) cutting out very intermittantly. It did this maybe once a week for months before I tracked it down. The car would die then start up fine. Finally the car died then it took a while before it started up and thats when I found the problem. The story doesn't end there however. I found later after a second relay went bad (contacts burned) that the air flow sensor switch that activates the relay to turn on the fuel pump was bad causing the relay to pull in/drop out all the time. So after a second relay change and cleanning up of the contacts inside the airflow meter things have been fine for years ever since.

Walt Barie
'80 528i
+ others

: Hey-
: I would appreciate a little diagnois/troubleshooting help...I was driving my '85 535i on a 200mile trip today, and had a wierd mechanical problem..

: I drove the first 45 miles fast, with no problems. I then stopped, picked up a friend, and began the next leg of the trip. After a short while, at 65-70 mph, 2-3K rpm, the car stuttered and lost power. I reacted by downshifting and pumping the pedal a bit, and it cleared up and drove fine. Seemed like a slug of bad gas or something... This happened sporatically for the rest of the day, and each time, it would seem to clear up with more gas/higher rpm. It seemed to happen when the motor was more unloaded and at lower rpm, such as when I had backed off of the throttle and was just mainaining speed.

: I filled 'er up last night, and thought I could have gotten some bad gas, so I added some fuel additive. This does not seem to have made a difference.

: My initial guess was fuel filter or something wrong with the fuel pump. On further thought and consultation with a motor-head friend, I am thinking it may be a partially plugged catalytic convertor.

: The car idles fine, and runs and accellerates OK otherwise.

: Before I sink a bunch of cash into a catalytic convertor or into random part replacement, I am looking for opinions...

: Any guesses on what the problem could be, or what a good troubleshooting approach would be?

: Thanks!

: Chandler

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: Could indeed be fuel system related. I had a similiar problem and it was the fuel pump relay (part of the combo relay) cutting out very intermittantly. It did this maybe once a week for months before I tracked it down. The car would die then start up fine. Finally the car died then it took a while before it started up and thats when I found the problem. The story doesn't end there however. I found later after a second relay went bad (contacts burned) that the air flow sensor switch that activates the relay to turn on the fuel pump was bad causing the relay to pull in/drop out all the time. So after a second relay change and cleanning up of the contacts inside the airflow meter things have been fine for years ever since. : Walt Barie : '80 528i : + others : : : Hey- : : I would appreciate a little diagnois/troubleshooting help...I was driving my '85 535i on a 200mile trip today, and had a wierd mechanical problem.. : : I drove the first 45 miles fast, with no problems. I then stopped, picked up a friend, and began the next leg of the trip. After a short while, at 65-70 mph, 2-3K rpm, the car stuttered and lost power. I reacted by downshifting and pumping the pedal a bit, and it cleared up and drove fine. Seemed like a slug of bad gas or something... This happened sporatically for the rest of the day, and each time, it would seem to clear up with more gas/higher rpm. It seemed to happen when the motor was more unloaded and at lower rpm, such as when I had backed off of the throttle and was just mainaining speed. : : I filled 'er up last night, and thought I could have gotten some bad gas, so I added some fuel additive. This does not seem to have made a difference. : : My initial guess was fuel filter or something wrong with the fuel pump. On further thought and consultation with a motor-head friend, I am thinking it may be a partially plugged catalytic convertor. : : The car idles fine, and runs and accellerates OK otherwise. : : Before I sink a bunch of cash into a catalytic convertor or into random part replacement, I am looking for opinions... : : Any guesses on what the problem could be, or what a good troubleshooting approach would be? : : Thanks! : : Chandler

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