MAF disconnect

[Johnny Danger]

Originally Posted by tommy583

The codes I had were P0102 and P0112. I cleared the codes and hooked the MAF back up. No codes on my way to work. I cleaned the MAF a few weeks ago, it didn't show any improvement. But it seemed to run quite a bit stronger with it disconnected. So i guess my next purchase will be a new MAF.

I thought so .

[pothole]

Check for air leaks, too. Unplugging the MAF will also effectively zap bad running due to leaks.

I ran my old BMW 328i with the MAF unplugged for four months including a track day with no ill effects, so I wouldn't worry too much - the ECO will just default to stored values that aren't too far off reality.

It will run a bit better with a good MAF plugged in, however.

[thstone]

Originally Posted by pothole

Check for air leaks, too. Unplugging the MAF will also effectively zap bad running due to leaks.

Can you explain? Even when running on the default maps with the MAF disconnected, wouldn't an air leak cause the engine to get more air than the default map expects resulting in poor running? I would expect an air leak to result in poor running either with or without the MAF. Yes?

[The Radium King]

ecu uses maf to tell it how much air the car is getting. air volume and rpm are used to look-up the required fuel amounts on the programmed maps.

if the maf isn't working the car will use the throttle position to determine how much air is getting in. should be pretty accurate, but can't compensate for pressure differences, etc.

if there is an air leak after the maf (ie, the aos system is often a culprit - failing aos causes excessive vacuum in the crankcase which collapses and cracks the oil fill tube which then allows air to be drawn in post-maf but pre-throttle body) then the ecu will get thrown off. not so with the throttle position sensor.

[tommy583]

The AOS was replaced last year. I don't think it had a total failure, but i was seeing a little smoke here and there.

[The Radium King]

when they replaced your aos, did they replace the oil fill tube as well? perhaps check it for cracks, as a bad aos can collapse and crack it.

[tommy583]

I replaced it and no i did not replace the oil fill tube. I'll take a look at it. Would the cracks be easy to spot with it still in the car? Is it a worse job replacing the fill tube or the AOS?

[Topless]

Originally Posted by pothole

Check for air leaks, too. Unplugging the MAF will also effectively zap bad running due to leaks.

I disagree with this. Unplugging the MAF removes it from the equation but does not affect intake air leaks. A significant air leak will be revealed in O2 sensor codes like 1128.