E46 318i M43B19TU Uneven / Irregular Acceleration

[sammcj2000 1]

I'm looking into a problem my friends E46 318i M43B19TU is having...

He's found that when he's driving he is getting irregular / uneven acceleration.

It's as if there are flat / dead spots on his accelerator but it's not FBW.

I've replaced his plugs and done a readout from DIS / GT1 but there aren't any errors?

It doesn't happen all the time, you can occasionally make an entire journey without it happening once. Then the next time it might do it every time you take off from stopped.

We're thinking...

-Fuel

-TPS

-Cam Position Sensor

-Coil

Edited December 6, 2010 by sammcj

[*Glenn* 854]

What motor ? M43, N42, N46 ??

[sammcj2000 1]

What motor ? M43, N42, N46 ??

Sorry, M43

[*Glenn* 854]

Sorry, M43

I'd be checking live data if no fault codes are being thrown. It's more than likely to be the MAF sensor. 12-16 KG at idle... 450-550kg at full throttle, under load while driving.

You absolutely sure there are no fault codes ? Check EGS & ABS for DME related fault codes as well. Also check system & charge rate voltages.

Edit: Any noises from the cat ? a blocked cat can also cause that

Edited December 5, 2010 by *Glenn*

[sammcj2000 1]

DIS does give a few errors but they're not really relevant and have been there for the last year at least:

-Missing auto gearbox (It's a manual)

-ZKE is complaining the burglar alarm siren is not responding.

-Occasionally get a "fuel too rich" code though this may have been left over from before he changed the O2 sensor a month or so ago.

-Can't check EGS for codes because he doesn't have one.

-ABS giving no codes.

We'll try cleaning the MAF & looking at the live data.

Thanks again for your help Glenn, as always it's appreciated.

EDIT: Cat doesn't make any sounds or smell like it's dying.

Edited December 6, 2010 by sammcj

[sammcj2000 1]

On idle air mass is at about 14.20.

At full load revving the buggeries out of the car it max's out at 211.

Here is the data from the car on idle:

[*Glenn* 854]

On idle air mass is at about 14.20.

At full load revving the buggeries out of the car it max's out at 211.

211kg is too low. Are you absolutely sure there are no other problems ? air leaks, CCV valve etc

At this point I'd be trying another MAF sensor. Was this low reading taken when the car was actualy playing up ?

[sammcj2000 1]

211kg is too low. Are you absolutely sure there are no other problems ? air leaks, CCV valve etc

At this point I'd be trying another MAF sensor. Was this low reading taken when the car was actualy playing up ?

The car appeared to be running alright at this time.

I couldn't find / hear any air leaks although I didn't do the open the oil cap while the cars running trick.

OK, We'll do some hunting for a MAF sensor, is it worth spending the extra for a new one rather than a s/h?

[*Glenn* 854]

Your call... I'd be fitting a new one, but first I would confirm that it was at fault.

[sammcj2000 1]

Your call... I'd be fitting a new one, but first I would confirm that it was at fault.

What would be the easiest way to test it?

Does this sound like decent advice to start with - http://forums.bimmerforums.com/forum/showt...d.php?t=1350994

and maybe http://bmwz8.us/vbb/showthread.php?t=290

[*Glenn* 854]

I would fit a new one and recheck my readings... something you can't do unfortunately... the tap test doesn't always work either. Using a scanner and reading the Kgh readings in live data while driving is virtually the same as using a dash cluster. The readings you are getting (210kgh) is too low.

[sammcj2000 1]

I would fit a new one and recheck my readings... something you can't do unfortunately... the tap test doesn't always work either. Using a scanner and reading the Kgh readings in live data while driving is virtually the same as using a dash cluster. The readings you are getting (210kgh) is too low.

OK, I wonder if it's the same sensor as in my E34? I'm guessing not.

We'll remove his and bath in IPA / ultrasound and see if the readings improve at all.

Also, I have just been informed that it's actually a M43B19TU not a B18 like I originally thought.

[*Glenn* 854]

PM the Vin # to me

[*Glenn* 854]

Also, I have just been informed that it's actually a M43B19TU not a B18 like I originally thought.

All that we have discussed so far doesn't change, the B19TU & B18 are basicaly the same as far as diagnosing faults are concerned.

[sammcj2000 1]

We've cleaned the MAF.

Acceleration is much smoother, but it's still maxing out at 230 at max throttle full rev's.

I used a GPS car timer to test the 0-100 speeds and estimated BHP based on weight and speed and I think they're a lot worse than a manual should be, on the net it looks like 0-100 should be about 10.4/sec.

Peak Wheel Horsepower: 52 kW

0-10 km/h: 0.89 sec

0-20 km/h: 1.91 sec

0-30 km/h: 2.89 sec

0-40 km/h: 3.94 sec

0-50 km/h: 5.29 sec

0-60 km/h: 7.35 sec

0-70 km/h: 9.03 sec

0-80 km/h: 11.10 sec

0-90 km/h: 14.18 sec

0-100 km/h: 16.79 sec

Edited December 7, 2010 by sammcj

[sammcj2000 1]

He just emailed me: "It did it again on the way home, but at WOT this time."

Is the MAF even sampled at WOT? doesn't the dme just use pre-set levels at that point?

Edited December 7, 2010 by sammcj

[*Glenn* 854]

He just emailed me: "It did it again on the way home, but at WOT this time."

Is the MAF even sampled at WOT?

Yes.. it still has to measure air temp and air volume (kg) for the DME

Edited December 7, 2010 by *Glenn*

[sammcj2000 1]

Sorry to wake up a dead post but...

Ross is still having this issue with his car.

Since the last post his pre-cat o2 sensor and air filter have been replaced.

He's just reticently noticed that the car is MORE responsive with the Air Con ON - (Go figure?)

What could this point to?

Thanks,