E36 Idle surging MAF or O2 sensor??

[Matich]

Recently bought a donor car for a 6 cylinder swap and have been doing basic fluid/filter changes with some new spark plugs etc, the car wasn't in the best shape but the intention was always to rebuild the engine (gaskets and such) before the swap. I noticed it felt down on power and was in limp mode and the owner said it was due to a faulty MAF.

I've noticed that the car bounces a lot at idle and constantly smells of petrol telling me that the car is running very rich. I first suspected that it was the maf because when i unplugged the sensor the idle would level out and stay consistent, however this would not allow me to rev much above 2-3 grand.

After searching for more answers I saw the possibility of the o2 sensor being faulty and it causing the dme (Bosch 402) to not go closed loop at idle.

I'm hoping it's just an o2 because the old hotwire maf's are expensive to replace (even a non oem), anyways check out the video and tell me what you guys think.

[jc43089]

Have you inspected/replaced your ICV hoses for leaks? With the MAF plugged in it is running according to how much air is going through the MAF. With the MAF unplugged it is just running the best it can according to TPS, RPM etc.

If there is air leaking in that is not measured by the MAF then it will run poorly at idle.

[Matich]

Before this video I had removed the intake manifold and inspected everything, reattached the hoses and gave them extra fastening with clamps/ties. I also cleaned the ICV with carb cleaner but the issue was still present

[guymandude]

Any codes?

[spyderg0d]

I vote 02 sensor. A quick test is to unplug it. But also, in an obdl echaust, a exhaust leak on 1 header will cause a proper 02 to send the faulty reading and then cause a surge idle. Just like connecting the 1 02 into 1 of the headers.

[atlantisvip]

I went crazy replacing parts trying to figure out the infamous NVM50 surge issue. Wound up being low compression on 2 cylinders. Do compression check.

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[Matich]

I went crazy replacing parts trying to figure out the infamous NVM50 surge issue. Wound up being low compression on 2 cylinders. Do compression check.

If it was low compression doesn't that mean the car would surge regardless if the MAF is unplugged or not? Mine idles fine when it's unplugged but of course I cant drive without a MAF

[atlantisvip]

Like I said, that was my issue. Would get real bad as it got hotter. You didn't do a compression check before buying an engine either way?

[Matich]

Nope I got the entire car for $400usd so the fact it could run and drive was enough, I planned to rebuild the engine anyways so imperfections didn't worry me.
Most people in my country want 1-1.2k for an M50 (not sure why they think it's worth so much), so I felt like this would be a good budget starting point for the project!

[guymandude]

My euro s50b30 has a surging idle when it goes into limp mode. It cuts timming and riches fuel mixture. Has happened numerous times for various reasons. Scan it, deal with problem, clear codes, and it runs fine.

[Chroniverous]

Did you find a fix for this? My car is doing the exact. same. thing. It is literally driving me crazy.

Disconnect MAF and it runs around 1000k idle but at least doesnt surge. No codes present. I have checked all hoses and what not but still its surging. I am going to disconnect the oxygen sensor this weekend and report back.

[guymandude]

Did you find a fix for this? My car is doing the exact. same. thing. It is literally driving me crazy.

Disconnect MAF and it runs around 1000k idle but at least doesnt surge. No codes present. I have checked all hoses and what not but still its surging. I am going to disconnect the oxygen sensor this weekend and report back.

Id pull your intake manifold and clean the icv replace the manifold gaskets. Or just fire aome seafoam at the icv while on

[RobinME28]

Did you also try connecting the MAF and de-connecting the ICV? I'm curious how the engine reacts to that.

[Chroniverous]

Recently bought a donor car for a 6 cylinder swap and have been doing basic fluid/filter changes with some new spark plugs etc, the car wasn't in the best shape but the intention was always to rebuild the engine (gaskets and such) before the swap. I noticed it felt down on power and was in limp mode and the owner said it was due to a faulty MAF.

I've noticed that the car bounces a lot at idle and constantly smells of petrol telling me that the car is running very rich. I first suspected that it was the maf because when i unplugged the sensor the idle would level out and stay consistent, however this would not allow me to rev much above 2-3 grand.

After searching for more answers I saw the possibility of the o2 sensor being faulty and it causing the dme (Bosch 402) to not go closed loop at idle.

I'm hoping it's just an o2 because the old hotwire maf's are expensive to replace (even a non oem), anyways check out the video and tell me what you guys think.

Did you find the solution for this? Im still trying to figure this out. My car is doing the exact same thing. I have noticed that the car is getting a lot of fuel, so much so that my oil is contaminated with fuel. Getting very frustrating. I have replaced every sensor.

Initially the Crank Sensor was bad, I replaced it and now it runs exactly like this.

[Chroniverous]

Recently bought a donor car for a 6 cylinder swap and have been doing basic fluid/filter changes with some new spark plugs etc, the car wasn't in the best shape but the intention was always to rebuild the engine (gaskets and such) before the swap. I noticed it felt down on power and was in limp mode and the owner said it was due to a faulty MAF.

I've noticed that the car bounces a lot at idle and constantly smells of petrol telling me that the car is running very rich. I first suspected that it was the maf because when i unplugged the sensor the idle would level out and stay consistent, however this would not allow me to rev much above 2-3 grand.

After searching for more answers I saw the possibility of the o2 sensor being faulty and it causing the dme (Bosch 402) to not go closed loop at idle.

I'm hoping it's just an o2 because the old hotwire maf's are expensive to replace (even a non oem), anyways check out the video and tell me what you guys think.

Anything, still having the same issues!

[Shamwhat]

Have you tried running it with the air box attached after cleaning the ICV? Mine wouldn't even run without the filter after I did the same thing; it also smelled like excess fuel. Maybe the film cools faster, giving a higher than normal airflow reading and then the DME compensates with more fuel. At any rate, it worked for me!