Weird Problem with the bimmer...

[Brew]

Well, I just drove back from Boston to Marshfield averaging about 90. I got off the highway and headed down some backroads when the engine basically stopped for a fraction of a second, then continued to run normally. The "check engine" light also flashed for a moment. This happened maybe 4 or 5 more times on the rest of my drive home, and each time the engine would basically "cut-out" for a tenth of a second or so. This problem has happened a few times before. Once it happened on the highway when I was doing about 110 up a hill, the other time when I had three people in the car, a loaded trunk, and three snowboards in a Thule box on the roof doing about 85. It seems to only happen when the engine is under heavy load.

I don't think that it could be a fuel related problem, like a bad pump or clogged filter, because they would usually make a car slowly stall as it ran out of fuel. Could it possibly be a bad ECU, maybe "telling" the engine that its hitting redline or something? I'm hoping that it is not anything too serious, but I would greatly appreciate any insight that anyone could give me.

For some background on the engine, it was rebuilt at approx. 80k miles because of a broken timing belt I believe, and has about 121k on it now. I replaced the timing belt, tensioner, water pump, etc. at 117k. It has a slight oil leak, but other than that runs great and pulls hard all the way to redline.

[nando]

was it cold outside?

this exact thing happened to me and a few other people on the 325ix mailing list, all within a few days of each other. it was really cold out (15-20 degrees) when my car did it on the freeway going 70mph, and it hasn't done it since. It ran fine otherwise, no loss of power. Since then I've reset the ECU and replaced my O2 sensor (not because of the wierd problem though). Still revs great and pulls hard.

None of us were able to determine what it was, but a few speculated on relays, fuel pump, or even the fuel pressure regulator. I don't think relays were the problem because electrical power wasn't cut off. maybe somebody else can shed some light on this?

oh, to reiterate, my check enginge light only flickered for a split second, in fact all i really saw was a red flash out of the corner of my eye. it did it 3 times and hasn't done it since, that was about a month ago.

[Brew]

Pretty chilly all three times it has occurred, now that I think of it. I know that it isn't a fuel pump relay because I recently had that get bumped out of its socket when I was driving and the car took a few minutes to die. I just hope that the engine is seizing or something. Its just a really, really weird problem.

[nando]

why would you hope the engine is seizing!! :shock:

in any case, the one thing that we all had in common was the low temperature - I'm thinking maybe the fuel lines were beginning to freeze. it was almost like the car died for a split second, but since i was going 70, it just kept going. isn't there a special fuel additive for this type of problem, to displace the water and keep the lines from freezing?

[James Crivellone]

Air Flow Meter, Speed Reference Sensor (does ur tach act up) Coolant Temp Sensor.



pick one :p I replaced my speed ref (which was faulty) and my AFM (which was also faulty) to solve my sudden power loss issue.

[nando]

describe your sudden loss of power.. because this was more like a blip, rather than a loss of power. I kept going 70 the whole time it was doing it.

[Brew]

why would you hope the engine is seizing!!

$hit, my bad. it was late when i was posting last night, i must have been sort of tired.

thanks for the quick replies guys. I'll check out those things you mentioned James.

[M42Technik]

describe your sudden loss of power.. because this was more like a blip, rather than a loss of power. I kept going 70 the whole time it was doing it.

I'm having the same problem too. My idle once in a while blips and the car almost cuts off, but jumps right back to idle. Never cut off though....

[m42technic]

02 sensor.

[M42Technik]

02 sensor.

Thanks my man.

[nando]

it didn't do it during idle in any of the accounts I read. My car idles fine.

anyway, I have replaced my O2 sensor since then (about a week or two ago). hasn't done it for a month, and I was replacing it anyway so I have no idea if that was the cause. I still think the cold weather was related somehow..

[Alex Mc]

This remark is directed towards James Crivellone,

I have replaced everything in the ignition system in my buddy's 1.3 Motronic 'i' 2.8L and i just called him after reading your post. He said his tach needle (only!) falls dead when the "cut" happens. So, my question is.. how did replacing the AFM come about? Did you replace that before the sensor and the problem persisted? Or did you have to still replace it after you repalced the Speed Reference Sensor?

Alex

[iXer]

Please check out my reply in the thread titled "Intermitten throttle/ignition cut?" :

http://www.r3vlimited.com/phpBB2/viewtopic.php?t=3187

[E30godz]

m42technic, you said the O2 sensor was the cause of the blip idle, almost dies but doesnt thing? mine does that!! i just replaced the oxygen sensor with the ford mustang one though...hrm...

[James Crivellone]

This remark is directed towards James Crivellone,

I have replaced everything in the ignition system in my buddy's 1.3 Motronic 'i' 2.8L and i just called him after reading your post. He said his tach needle (only!) falls dead when the "cut" happens. So, my question is.. how did replacing the AFM come about? Did you replace that before the sensor and the problem persisted? Or did you have to still replace it after you repalced the Speed Reference Sensor?

Alex

i had the speed ref sensor go out before the AFM did, and when it died, I was still in gear, but the tach was at 0, and when it acted up the tach would go nuts and drop.


now with the afm, it does it so fast that the ECU did not notice, so the tach stayed at whatever then engine speed was at.

the final fix to my problem was the AFM