IAT - Is it possible for this sensor to cause misfire?

[dude8383]

For reference:

13621725323

Is this thing capable of causing a misfire? I'm just trying to diagnose the misfire issue on my S52. The donor car ran smooth as butter prior to the OBD1 swap... which has me convinced that either my MAF is faulty or the IAT is.

The reasoning behind this is the fact that when my stroker blew up, it regurgitated coolant out of the air intake. So far, cleaning the MAF has improved the way the car runs but still suffers from a misfire. I have a MAF thats in the mail already, should have it tomorrow.

So do you guys think that coolant passing over the IAT could have possibly made it malfunction? I cleaned the intake manifold thoroughly with brake cleaner and flushed it with water as well...let it dry overnight and installed it.

[dude8383]

Quick update, I checked resistance for both the sensor thats in there now and the new one... both are reading within spec it seems.

This issue is really beginning to point at the MAF

[MR 325]

You don't know anyone with a MAF you could test with?

[328ijunkie]

Unplug the MAF. Try running it like that for a little and see how it runs.

[dude8383]

You don't know anyone with a MAF you could test with?

My buddy has an e36 325I but his maf ain't functioning properly either. I've been trying to find someone locally that I could lend one but haven't had any luck. Might have to stop by my buddy's place in Jersey.

Unplug the MAF. Try running it like that for a little and see how it runs.

Unplugging it makes it run smoothly. Is it okay to drive it like that??

Another strange observation, when swapping MAF sensors the car runs smoothly for the first 2-5min at idle. As soon as I give it any throttle input it begins to misfire...

MAF right?

[328ijunkie]

Its okay to run with no MAF, not idea but it doesnt hurt anything. The ECU defaults to a safe map because it has no idea how much air is coming into the engine.

This is not "Alpha-N" as some people assume.

[dude8383]

Its okay to run with no MAF, not idea but it doesnt hurt anything. The ECU defaults to a safe map because it has no idea how much air is coming into the engine.

This is not "Alpha-N" as some people assume.

Interesting. Good to know!

Also started a thread on bf:

http://forums.bimmerforums.com/forum/showthread.php?t=1711517

The game plan is to swap plugs as soon as I get home. I completely overlooked the fact that the car ran SUPER rich prior to cleaning the MAF.

[trackjunkie21]

IAT wouldn't cause it to misfire, it would have a weird Idle, but it shouldn't be causing anything like that. A combination of plugs and the MAF can be causing your car to be running rich, I would swap out plugs either way, The NGK's are your best bet. part number: 12-12-9-064-619-M220. Bosch 4 tip plugs are a waste.

[328ijunkie]

NGK Vpower: 2.10 at AAP!

[jrdeamicis]

Unplugging the MAF and it running smoother means you have a mixture issue, (MAF, O2, Or Coolant Temp)

Check all 3. You can meter the MAF while it is running with a volt meter set on 20VDC.

The O2 you can monitor also with a meter. You should use a watch to check it out though.

Coolant temp also with a DVM. Its resistance based.

[dude8383]

IAT wouldn't cause it to misfire, it would have a weird Idle, but it shouldn't be causing anything like that. A combination of plugs and the MAF can be causing your car to be running rich, I would swap out plugs either way, The NGK's are your best bet. part number: 12-12-9-064-619-M220. Bosch 4 tip plugs are a waste.

Yeh, I'm slowly ruling that out as the cause.

Definitely going to pick up those NGK's when I get back from the track, for now, I will swap out to the Bosch plugs I have that are NIB.

NGK Vpower: 2.10 at AAP!

Are these single tip?

[328ijunkie]

Yes.

[dude8383]

Unplugging the MAF and it running smoother means you have a mixture issue, (MAF, O2, Or Coolant Temp)

Check all 3. You can meter the MAF while it is running with a volt meter set on 20VDC.

The O2 you can monitor also with a meter. You should use a watch to check it out though.

Coolant temp also with a DVM. Its resistance based.

Should I have the car running when checking the MAF? Or just with ignition on? I did test the MAF though, its getting proper voltage. Unless I'm completely missing your point.

Not sure how to check o2 sensor though. Am I checking for power at a specific place?

Coolant temp I will definitely check for resistance. The dual pin one correct?

[dude8383]

Yes.

I thought the 2 tip ones were better? In any case, I could probably snatch these up on my way down to Shenandoah.

[328ijunkie]

I prefer the single's

Oh and you want to measure MAF voltage going back to the ECU when the engine is running. It sends a 0 to 5 volt signal back to the ECU based on how much air is coming in.