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-   -   Intermittent power loss, fuel pump problem? (

hyksos 05-27-2011 07:43 PM

Intermittent power loss, fuel pump problem?
About a month ago I had a check engine, coil pack #6 gone bad, the engine was vibrating and had no power, replaced the coil pack, check engine gone, no more vibration, power was back.

But after that I saw some power loss from time to time and I made sure it was not related to the transmission, I did test in manual mode without shifting only playing with the throttle.

So here are the symptom, when I push throttle hard (about 75%), it will have power available right there, it accelerate quickly up to 6000+rpm, then shift, transmission shift no problem, then it's like if the engine is stalling, no power at all, it accelerate slowly... then suddenly BANG power is back.

The reverse can happen aswell, I push the throttle then the engine accelerate very slowly ... then out of sudden 100% power is back and BANG it accelerate quicky... all on the same gear!!

I have no check engine, if it was the MAS/MAF the check engine will go on immediately no? So do you think my fuel pump is possessed? :(

hyksos 05-27-2011 07:50 PM

More info, this is not due to gas quality, the engine idle perfectly, very steady and since the first time it happened, I went through at least 2 full tank of gas, always premium.

hyksos 05-29-2011 08:58 AM

So, no one else had this problem? :(

UncleJ 05-29-2011 10:04 AM

I had a MAS/MAF problem that was "itermittent" in that it only failed part of the time, but did not always throw a code (according to the tech). Prior to that (like a week) I had the fuel return valve in the tank replaced -- it did throw a code, but I wonder if it was not the MAS/MAF that was the real problem. No matter, both were done and the car runs even better now -- with better mileage as well. The point here I guess is that some of these things can fail without throwing a code, or will fail part of the time. If this were me I would take it in to the dealer or a premium BMW Indy shop.:dunno:

hyksos 05-29-2011 10:23 AM

I have an extended warranty on it but not from BMW ... and they are very picky about doing repair, if it don't throw a code and is still drivable they won't do a thing, unless I have solid proof that a part is defective (They are not willing to change part at random to see if this fix the problem) :(

Thanks for the tip, my ODBC reader can read the MAF data live, I'll go check what happen to the MAF data when I have this problem.

hyksos 05-30-2011 07:27 AM

After some test with my ODBC reader, the MAF seem working perfectly.

But I found something very strange with the throttle position... its value decrease dramatically when my power loss occur, but I'm not moving my foot, it's still at like 75%....

Can I have a defective gas pedal? Or is it some electronics that tune down the throttle because of some others problems??

m3bmw99 11-06-2012 07:20 PM

I am having this exact problem with my 2007 X3. It is more apparent at full throttle, engine struggles to get to redline, it shifts then immediate loss of power followed by gradual increase in power again. No codes. Had it to dealer today and they reprogrammed DME and EGS and it is still happening! What did they do to fix your car hkysos?

hyksos 11-06-2012 07:36 PM

Oh, I forgot to update this thread.

My problem was the radiator fan ..... it was not working anymore, I found it the hard way in the traffic, my engine temperature increased dramatically when I was not moving.

I know it sound very strange that the 2 problem can be related, but they changed the fan under warranty, they did absolutely nothing else and my power loss problem was gone... it's been more then a year now and I never had the problem once...

What is strange is that when I had power loss, the engine was not overheating, my theory is that the engine might have some protection circuity that detect fast temperature increase or something like that, that cut power to the engine to protect it.... I really don't see anything else that can explain that :dunno:

hyksos 11-06-2012 07:41 PM

oh and to test if your fan work, all you have to do is start the engine and turn the A/C on at full power, open the hood, the fan should be running. (You can actually hear it outside without even opening the hood)

m3bmw99 11-06-2012 08:40 PM

thanks for your reply. i will have to try that tomorrow, unfortunately it's not really A/C weather so may be difficult to simulate....that said I know there is definitely a problem and will bring your experience to the dealerships attention. curious, did your fan simply stop working, or was it an intermittent problem? I am wondering if the fan might be drawing too much and maybe taking away power from other components or alternatively putting too much strain on alternator....

hyksos 11-06-2012 09:49 PM

The fan was not working at all, but the X3 does not overheat easily, even with the fan not working at all, the engine was keeping normal temperature 99% of the time, I only saw overheat when I was stuck in traffic for long time.

Oh and the A/C was very weak at red light and working like a charm when I was moving, but I never did the association with the broken fan :rofl:

Supercourse 11-06-2012 10:31 PM


Originally Posted by hyksos (Post 7180535)
The fan was not working at all, but the X3 does not overheat easily, even with the fan not working at all, the engine was keeping normal temperature 99% of the time, I only saw overheat when I was stuck in traffic for long time.

Don't be misled by the BMW temp. gauge.

It is damped more than the average so that owners don't complain to dealerships about small fluctuations in operating temp.

You will notice when warming up that the temp. gauge moves to the middle and stays there.
In fact, the the full operating temp. is not achieved until several miles or minutes after that.
But the temp. gauge doesn't show you that.

Similarly, if you have a coolant leak, or your cooling fan stops working, the temp. gauge will not alert you to that right away.

Quite a few owners have commented how the gauge can quite rapidly go from the center to the red.

So I think you were overheating when the fan failed and power loss certainly follows.

The power loss could come and go as the natural air flow to the engine changed with speed.

Or maybe your fan was in fact failing intermittently before completely dying.

You maybe dodged a bullet there and caught it just in time.

hyksos 11-06-2012 10:42 PM

I don't think the temperature gauge is that bad... when it is -30 here in Canada, it take forever to reach center.

And when I got the overheat in traffic, I turned my A/C off and turned the heat all the way up, the temperature on the gauge decreased enough to allow me to get to destination.

Also, I did my test on the highway, at good speed, so there's enough air flow going in the radiator to keep engine cool.

So I'm convinced that the engine was not over heating.... it's something else, but related somehow...

m3bmw99 11-10-2012 11:14 AM

Update: Picked up my car from the dealer yesterday, it was in fact the radiator fan! Dealership confirmed that the radiator fan had failed and as a result the computer was in a protective mode so it was operating with reduced power (not like limp mode in most of the newer bimmers). Fortunately, my car registered a fault and the "EML" (engine management electronics) light came on when I was bringing it back to the dealer, so it made it easier for them to diagnose. Thanks to all on this forum, I was able to diagnose the problem and lead the tech to the problem.....without the code they would have been totally lost....last day of CPO warranty!

hyksos 11-10-2012 02:46 PM

Great, on mine, the EML never came on .... I think they are using a damped EML :rofl:

Seriously, as soon as the engine go in protection mode, the EML should go on.

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