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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Mon, Feb-12-2018, 07:03:09 PM   #1
spnsprt
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Default MAF issue or something else?

Hey folks,

I've got a 2003.5 M3 that was one of the dinan ones that came with pretty much all their stuff. When I got it, it had the stoke intake on with the MAF unplugged. The previous owner (who is a mechanic) told me that when he plugged it in the car would stall and bog, which he thought was due to the Dinan map getting confused with the stock intake.

Since then, I've been able to get a dinan CAI on this forum and after installing it and resetting the computer, the car is able to run with the MAF plugged in, but when pulling to a stop the idle drops pretty low and one time the car just stalled when i turned off the AC.

Do you folks think I have a faulty MAF? Nothing like this happened when I had the MAF unplugged. Could it be related to one of the codes on the comp for implausible engine temperature?

Thanks!
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Old Mon, Feb-12-2018, 08:29:42 PM   #2
PenguinScotty
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Default Re: MAF issue or something else?

When you unplug the MAF, the car goes into Open-Loop, essentially bypassing a lot of sensors, hence why your car ran fine without it plugged in.

Regarding your issue, there are several factors that could affect this, including but not limited to Vacuum leaks, O2 sensors, MAF sensor, TPS etc.

I had a similar issue, and mine was related to the MAF, but it may not be the case for you.

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Originally Posted by spnsprt View Post
Hey folks,

I've got a 2003.5 M3 that was one of the dinan ones that came with pretty much all their stuff. When I got it, it had the stoke intake on with the MAF unplugged. The previous owner (who is a mechanic) told me that when he plugged it in the car would stall and bog, which he thought was due to the Dinan map getting confused with the stock intake.

Since then, I've been able to get a dinan CAI on this forum and after installing it and resetting the computer, the car is able to run with the MAF plugged in, but when pulling to a stop the idle drops pretty low and one time the car just stalled when i turned off the AC.

Do you folks think I have a faulty MAF? Nothing like this happened when I had the MAF unplugged. Could it be related to one of the codes on the comp for implausible engine temperature?

Thanks!
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Old Mon, Feb-12-2018, 09:20:55 PM   #3
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Default Re: MAF issue or something else?

Thanks that's super helpful. Do you think there's a good methodical way for me to go about diangnosing it? Or shold I just replace the MAF, see what happens, replace O2 sensors, see what happens, etc?

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When you unplug the MAF, the car goes into Open-Loop, essentially bypassing a lot of sensors, hence why your car ran fine without it plugged in.

Regarding your issue, there are several factors that could affect this, including but not limited to Vacuum leaks, O2 sensors, MAF sensor, TPS etc.

I had a similar issue, and mine was related to the MAF, but it may not be the case for you.
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Old Mon, Feb-12-2018, 09:43:26 PM   #4
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Default Re: MAF issue or something else?

Not sure what the issue could be but my car would stall with a K&N intake because it did not have the air straightener mesh thingy in front of the MAF. Does the Dinan intake have one?
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Old Mon, Feb-12-2018, 09:52:06 PM   #5
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Default Re: MAF issue or something else?

I don't think it does. I wonder if I could pull the mesh thingy out of the stock exhaust though.

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Not sure what the issue could be but my car would stall with a K&N intake because it did not have the air straightener mesh thingy in front of the MAF. Does the Dinan intake have one?
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Old Mon, Feb-12-2018, 10:10:22 PM   #6
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Default Re: MAF issue or something else?

Exhaust? I assume you mean the stock intake? I would recommend giving that a try to see if it fits. I know people had luck doing that with the K&N intakes. I just switched mine back to stock and it fixed my issue.
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Old Mon, Feb-12-2018, 11:05:56 PM   #7
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Default Re: MAF issue or something else?

Sorry, meant intake!
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Old Tue, Feb-13-2018, 12:06:16 AM   #8
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Default Re: MAF issue or something else?

Quote:
Originally Posted by spnsprt View Post
...Could it be related to one of the codes on the comp for implausible engine temperature?
I think a bad coolant temp sensor could cause weird stuff like this, the one for engine temp and not the cluster gauge. Either way, are you saying you have multiple codes showing up after a scan? What specific codes do you currently have?
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Old Tue, Feb-13-2018, 12:28:13 AM   #9
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Default Re: MAF issue or something else?

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Originally Posted by E30User View Post
I think a bad coolant temp sensor could cause weird stuff like this, the one for engine temp and not the cluster gauge. Either way, are you saying you have multiple codes showing up after a scan? What specific codes do you currently have?
Could definitely be the case.

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Originally Posted by ctres View Post
Not sure what the issue could be but my car would stall with a K&N intake because it did not have the air straightener mesh thingy in front of the MAF. Does the Dinan intake have one?
Currently running a aFe intake, which does not have the mesh, without issues. Only weirdness i've run into was when the filter was off. Effectively any little gust upset the car, so maybe the mesh does have some sort of effect on it.

Quote:
Originally Posted by spnsprt View Post
Thanks that's super helpful. Do you think there's a good methodical way for me to go about diangnosing it? Or shold I just replace the MAF, see what happens, replace O2 sensors, see what happens, etc?
Swapping out the O2s and MAF will add up quickly (ask me how i know ). I grabbed myself a


, which is able to display real-time readings of several sensors. It showed that my MAF read an intake air temp of 150+ and that the MAF readings jumping around severely as soon as it went into closed loop.

It will also allow you to check the O2 sensors, how quickly they react/adjust the mixture as well as the general difference between cylinders 1-3 and 4-6 as well as Cat efficiency. Only the upstream O2s will affect the air/fuel ratio, however.

You can also try cleaning the MAF. It didn't help me, sadly, but worth a shot, if you don't want to spend 100+ on a new one.

Sadly can be frustrating to trace these things down.

Out of curiosity, since the MAF was unplugged, was the CEL not on?
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Discussing MAF issue or something else? in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)