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Author Topic: Surging Idle after motor swap  (Read 11301 times)

ding

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Surging Idle after motor swap
« on: November 28, 2013, 06:56:27 AM »

First of I wanted to state I in know way think this is related to the tune or ECU,  I just wanted to see if anyone had any ideas one what to try to fix this issue.

I'm in the process of swapping a m52 into my 1992 325i, using an 95 m3 harness. Got the new to me motor, did all the gaskets, other than head and timing cover, got the sensors from a 93-95 that I needed, knock, cam, and coolant temp adapter. Moved over my crank sensor from my 92, as well as my ICV and CCV setup. Using pink top injectors, OBD1 fuel rail and m50 manifold, have tried both an 93-95 maf, and a 3.5 maf from a 540.

Started buy getting the motor in and not being able to start, first found I had be trying to pump fuel into the return line, as I swapped the lines that connect right buy the throttle body. Once I figured that out, I found that not having the TCM plugged into the chip, means it doesn't start. So I plugged that in then it started fine, but I get this surging idle, which you will see in the attached video, goes from 1200 to 3k. I have swapped ICVs, checked for vacuum leaks, and ran a peake research tool on it. The main code I'm getting is a Intake Air Temp, error, and a Control Supply Unit error. Now these could be to do with me testing and trying things when I was working to get it to idle correctly. Disconnecting TPS, or MAF, makes the issue much worse. Disconnecting crank sensor changes nothing. Disconnecting ICV seemed to make it just a bit worse. And as you'll see in the video, disconnecting the elbow just a bit to let in more air, past the MAF, makes it idle better, but still higher rpms, like 1500.

So it seems I'm running super rich. I haven't connected my wideband to test, but it seems to be the issue. So I'm looking for ideas here. I'm thinking of testing a new fuel rail and/or injectors with a new fuel pressure regulator, as I wonder if I broke it, pushing fuel into the wrong side of it. Also I wonder if maybe my crank sensor could do this, but doesn't seem likely.

Lastly two other issues that may or not be related, my 95 engine harness's x20 round connector is missing pins 1,2,3, and 9. Where my chassis side of that connector on my 92 325i (was an auto) is missing 1,2,9,10. So I'm not sure if that will cause any related issues, I'm doubting it, but I'd like to know what it effects. And lastly an relay back by the heater core and brake booster is making a noise like a relay flipping on and off.

Thanks for any help, I'm going to keep working on it, but any pointers would be great.

http://youtu.be/Ts8umJCAScQ
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ding

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Re: Surging Idle after motor swap
« Reply #1 on: November 29, 2013, 02:02:42 PM »

Ok wanted to update, in case ether I figure it out soon or anyone has some ideas of of what I have now found.

I have changed out the Fuel Rail, Injectors, and Regulator, same issue. Then I went through the wiring with an OHM meter and found the vanos and intake air temp sensor were swapped. Switch this back and then reinstall the intake and everything, still did it, so I pulled the elbow a bit and let it smooth out and then once it got warm I put the elbow back on and it was idling fine. So then I let it warm up a bit and gave it some throttle but it fulls off, just like how it did before at idle, but now on throttle. So ether I still have some wiring issue, or maybe my crank sensor is causing this?? Still haven't replaced it yet. I'm letting the motor cool back down and I'm going to try at it again later today.

As for the x20 connector being different I found this thread.

http://forums.bimmerforums.com/forum/showthread.php?1884583-A-318Ti-6cyl-swap-and-supercharger-build/page4

Which has a ton of info on that connector and found that seeing my car use to be an auto is why those pins are different. This explains why my reverse lights don't work.

Again any info on my issue would be great, and hopefully if someone runs into this same issue in the future all my info here will help them.
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ding

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Re: Surging Idle after motor swap
« Reply #2 on: November 30, 2013, 08:39:21 AM »

Another update here,  okay, so after talking with a friend he suggested maybe the coolant temp sensors were reversed, so I pulled up my instructions from turner for the coolant wiring adapter and found that yes in fact it does matter which coolant sensor wire is plugged into the which part of the harness, the one with the yellow wire needs to be plugged into the longer of the two plugs.  I did this, and now it only maybe revs up one or two times on start, and then settles down to 950rpms.  Now when I try to hold 3k or so rpms it will drop and pick back up again, as seen in this video.

http://youtu.be/5yTIDW9YeSo
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ding

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Re: Surging Idle after motor swap
« Reply #3 on: December 02, 2013, 06:18:31 AM »

Ok so its ether the tune for the 3.5 maf that is listed here or the 3.5 maf itself. As when I switched to the m50 performance tune and put my 3.0 maf in place it runs fine.
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millerperformance

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Re: Surging Idle after motor swap
« Reply #4 on: December 12, 2013, 06:54:17 PM »

Did you get that new maf in there?
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ding

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Re: Surging Idle after motor swap
« Reply #5 on: December 17, 2013, 01:32:07 PM »

Well I have my new maf, but haven't tried it yet, as I've been running my turner chip that was made for this motor, but with a 3.0 maf. 

But I'm having a new issue, that might be related to why my 3.5 maf didn't work.  With the 3.0 maf plugged in, my afr is maxing the gauge out on rich, and it smells really rich, like burning your eyes rich.  If I unplug the maf it goes to 14.3,  its cold. . Before I started I had new cam, and knock sensors, and I just replaced the crank sensor.  So I'm unsure on what to try next, I'm debating on trying the war chip again with 3.5 maf to see where my AFRs are at.
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