2002 318 E46 - Low Power when Accelerating at low revs - BMW Forum

sPoNgE-SA · 11-18-2008, 02:39 AM

I have a 2002 318 all stock with 128 000 KMS. The problem is that when I go to let out the clutch I rev it to about 700 rpm and start disengaging the clutch. Some times the power will drop to about 400 rpm and I will kill the car. I checked it in neutral and just gave it a little gas to bring the rpm,s to 1000. When I did this it went to 1000 but then dropped to about 400 and then went back up to 1000 again and then just fluctuated between the 2 points. This is my first BMW so I have no reference but the car seems to run great aside from this. The fuel mileage is normal from what I have read and it seems to have real good power still. I had the following changed, oil, plugs, air filter, Fuel Filter which was really dirty and the middle box cat changed, but it still does this. This doesn't always happen. Sometimes it works perfect. It happens when the car has warmed up when the revs are lower. I have no lights coming on as far as check engine or anything else. Can someone help me with this and if possible let me know how to fix it. I haven't had the MAF sensor checked. What is the sensor on the exhaust near the middle box?

One more thing, when I rev the go when it's warm it sounds like it's struggling to breath, exhaust sounds blocked.

marti5 · 11-18-2008, 09:42 AM

Ok, The sensor on the exhaust is the o2 sensor which will make it idle very bad if its shot, as for the MAF, with the car running, unplug it if there is no difference in the running the MAF is shot, the quickest way to find out is to have a full diagnostic check.

sPoNgE-SA · 12-01-2008, 09:15 AM

Hi Marti,

I've had the car on 3 different computers as well as at the BMW Dealer and nothing comes up. They did a lift on valves but haven't tested the car yet.
If I unplug the MAF (on the airbox) will the car lack power? Example revs take longer to drop ? They keep saying it's the crankshaft sensor as well.
The O2 sensor is on the exhaust near the Fuel Filter correct?

sPoNgE-SA · 12-08-2008, 08:31 AM

My car was at BMW and they raised the valves electronically. Anyone know how this is done and works? My car stopped for a few days and it came back. So far it's only happened once. Flat line between 1000RPM & 2000RPM. Revs go up and down then it corrects itself and then its fine.

marti5 · 12-08-2008, 09:55 AM

Hi, Again, been busy, from what you say in post 4 it sounds like the MAF, but ...... in post 3 you say the revs die when unplugged whic says the MAF is working,so its a toss up between the crankshaft and camshaft sensor, hard to say, it should come up on the diag, but no! does it do it when only 1st started and cold, if yes its the crankshaft sensor, if all the time hot or cold I would go with the camshaft sensor, but I still dont understand why its not showing up, so we go back to basics, unplug the camshaft sensor, no difference its shot, same with the crankshaft sensor.

But then the revs go up and down thats pointing at the MAF for sure. then theres the throttle body...........give that a clean.

Pity the car wasnt outside my house, we'd have it sorted.

sPoNgE-SA · 12-16-2008, 11:19 AM

Hey Marti,

Thanks for your response man. Ok BMW said they raised the valves electronically. Not 100% what this means but the problem of cutting out and revs going up and down has gone away for about 1.5weeks. But the car lacks power at occasions but only when it's warm. This only happens at pull off between 1000 and 2000 RPM. It's almost like it's struggling to breath and then it goes away. Still no errors on diag tests :-( I had the cat converter replaced but that's not it either. Starting to think I should of gone straight 6 :-).

marti5 · 12-16-2008, 11:26 AM

I did have that lack of power, like you, last week I fitted one of these:

E38 E39 BMW 5 & 7 SERIES 740 535 540i K & N AIR FILTER on eBay, also, Performance Tuning Parts, Car Tuning Styling, Cars, Parts Vehicles (end time 20-Dec-08 00:00:39 GMT)

It now goes like shit off a shovel, and the sound when you stick the gas down is well awesome.

Maybe there's a leak in one of your air intake hoses, another thing did you change the o2 sensor when you changed the cat.

sPoNgE-SA · 12-16-2008, 11:34 AM

ok cool, but this wont replace one of those hoses so replacing this might not fix it because I will still have a broken hose. Any idea which hoses to check

marti5 · 12-16-2008, 11:39 AM

The problem one is normally the one with the MAF in, which goes from the MAF to the throttle body,this is 99% the culprit, take it off and give it a damn good look over, whilst your there give the throttle body a good clean.

sPoNgE-SA · 12-16-2008, 11:45 AM

Know of any DIY's on this. Haven't had the car that long now. But worked for 7hrs on the motor :-) Had the car for about 2months. Had to do this after having a Toyota and working on everything i had to. Also nice to know what has been replaced and placed in my motor.

marti5 · 12-17-2008, 03:32 AM

You will find alot a good info on you model here:

BMW E46 DIY (Do It Yourself)

sPoNgE-SA · 12-18-2008, 02:34 AM

Thanks Marti,

One more thing, that air intake hose. Is it the one that's next to the MAF? I see the pipe is thin then goes onto a thicker soft rubber at the end where it joins onto the Main Intake Pipe.

Is this the correct one?

marti5 · 12-18-2008, 04:10 AM

Top left:

RealOEM.COM * BMW E46 318i HOT-FILM AIR MASS METER

sPoNgE-SA · 12-18-2008, 07:14 AM

ok right, that's way you said I should clean the throttle at the same time. So I should check that entire large air intake pipe. (Number 4 in diagram) What should I clean the throttle with? I know Wynns does a engine part clean. What you suggest ?

marti5 · 12-18-2008, 09:37 AM

Yes #4, clean T/body with either carb cleaner in an areosol can or meths on a cloth and old tooth brush, DONT NOT use petrol,thinners, or white spirit.