3.0 P0102 Maf non running issue

[n3il123]

I've got a z3 3.0 that seems to not want to play any more.

Symptoms are:

Got it out for its MOT after a long lay up, drove around fine, then on the way home slowed down to go round a junction, low revs the car wouldn't accelerate or rev, almost like the throttle cable had snapped. Minute or so later and it suddenly went again, all fine.

Took the car out a couple more times and it started to do it with more regularity.

Read the codes and its P0102 Mass or volume air flow circuit low input.

I've taken the Maf out and sprayed all the way through with contact cleaner, reassembled and now the car idles roughly and won't rev at all! (progress ... not!). I've tried disconnecting the cable and this makes no difference.

So i'm after some advice about where I go from here? I'm guessing its an electrical issue somewhere but i'd like to make sure that I have ruled out as much as possible before spending ~£200 on a new maf sensor!

Any pointers would be gratefully received!

[d_a_n1979]

More than likely the cam or crank sensor

But do check to see if there are any splits in the air intake boot from the MAF back to the throttle body; if it's taking extra air in there, it'll run lean and rough.

Have you tried to run it without the MAF too (ie. unplug it and start it up and see how it runs)?

If your engine has the DISA TOO (assuming it does being the M54 lump); the large O ring seal that sits between the DISA and intake mani can perish and let in air too; again, that'll lead to lean running/codes/rough running etc

[n3il123]

Thanks, yes tried running with the maf unplugged and is the same.

I'll get out and check the inlet pipe and disa. Would the cam/ crank sensors not throw their own codes?

[RUSSELLM]

Is it 3 wires are going to the sensor ?

I’d expect the engine ECU to be trying to read through the sensor, to detect it’s signal output, and also to see if it’s connected. A faulty sensor could give you ‘open/close/short to power/short’ to ground’ faults.

Edited by RUSSELLM on Thursday 3rd October 19:27

[d_a_n1979]

n3il123 said:

Thanks, yes tried running with the maf unplugged and is the same.

I'll get out and check the inlet pipe and disa. Would the cam/ crank sensors not throw their own codes?

Sometimes they do, sometimes they don’t. Can be a sod and a guessing game. I generally go for the cam sensor.

FYI this is one of the few times you need to buy OEM BMW as well, the aftermarket sensors are crap at best

[E-bmw]

It is quite possible that you have induced an air leak in the intake boot, take them all off & have a good check for splits.

In real terms that engine should run 95% perfect with the MAF completely disconnected, I had similar symptoms to your initial report with my e36 2.8 which is very similar & had to unplug the MAF to drive the car to get a replacement which cured the issue.

If you need a replacement DON'T GO CHEAP they only like OE MAFS & many other sensors.

[n3il123]

RUSSELLM said:

Is it 3 wires are going to the sensor ?

I’d expect the engine ECU to be trying to read through the sensor, to detect it’s signal output, and also to see if it’s connected. A faulty sensor could give you ‘open/close/short to power/short’ to ground’ faults.

Edited by RUSSELLM on Thursday 3rd October 19:27

Yes 3 wire sensor, I was wondering if there was a way to check with a meter that everything was ok up to the socket?

[n3il123]

E-bmw said:

It is quite possible that you have induced an air leak in the intake boot, take them all off & have a good check for splits.

In real terms that engine should run 95% perfect with the MAF completely disconnected, I had similar symptoms to your initial report with my e36 2.8 which is very similar & had to unplug the MAF to drive the car to get a replacement which cured the issue.

If you need a replacement DON'T GO CHEAP they only like OE MAFS & many other sensors.

Which would suggest that as it is the same whether connected or not that the issue is something other than the maf

[d_a_n1979]

n3il123 said:

Which would suggest that as it is the same whether connected or not that the issue is something other than the maf

Cam sensor or extra air being sucked in after the MAF or via the DISA

[RUSSELLM]

n3il123 said:

RUSSELLM said:

Is it 3 wires are going to the sensor ?

I’d expect the engine ECU to be trying to read through the sensor, to detect it’s signal output, and also to see if it’s connected. A faulty sensor could give you ‘open/close/short to power/short’ to ground’ faults.

Edited by RUSSELLM on Thursday 3rd October 19:27

Yes 3 wire sensor, I was wondering if there was a way to check with a meter that everything was ok up to the socket?

I don’t work on BMW’s, but on our cars, you’re looking for a 5v+ supply, 0v- supply ground, and 5v+ on the signal wire.

With the connector plugged in, the signal voltage drops considerably, to around 2.5v+ as it reads through the resistor in the sensor.

If you had an induction pipe problem, I’d expect to see a ‘correlation’ DTC.

Can you clear the DTC ?

If so, I presume it comes back after the engine’s been run ?

[E-bmw]

n3il123 said:

E-bmw said:

It is quite possible that you have induced an air leak in the intake boot, take them all off & have a good check for splits.

In real terms that engine should run 95% perfect with the MAF completely disconnected, I had similar symptoms to your initial report with my e36 2.8 which is very similar & had to unplug the MAF to drive the car to get a replacement which cured the issue.

If you need a replacement DON'T GO CHEAP they only like OE MAFS & many other sensors.

Which would suggest that as it is the same whether connected or not that the issue is something other than the maf

Which is exactly why I said the bit about the air leak now being likely.

But then as he also described the original issue differently, I believe he could have 2 issues.

Do try to keep up.

[n3il123]

E-bmw said:

Which is exactly why I said the bit about the air leak now being likely.

But then as he also described the original issue differently, I believe he could have 2 issues.

Do try to keep up.

I obviously missed the ? From the end!