Author Topic: Helpppp 94 m42 swap, troubleshooting  (Read 2384 times)

Uniquestrain

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Helpppp 94 m42 swap, troubleshooting
« on: April 25, 2013, 04:17:45 AM »
Okay so i swaped my 91 m42 to a 94 m42 and when i finally put it in the car it started right up
After a little while of test driving it, it started to idle low and it got worse the more the car was driven
Now the car wont start and dont know what the problem might be
It does have spark...but the top crankshaft sensor is broke alittle when in the process of doing the swap.

DesktopDave

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Re: Helpppp 94 m42 swap, troubleshooting
« Reply #1 on: April 25, 2013, 07:25:44 AM »
Try a stomp test - see what the motor thinks is wrong.  Give us some details on the swap - where the motor came from, what the compression readings are, any problems you ran into doing the install, etc.

The cam sensor should have about 1280 ohms resistance on pins 1&2 and very high resistance between pins 1&3 and 2&3.  Crank sensor should have about 640 ohms between 1&2.  If the crank sensor is damaged it won't fire up the fuel pump.

If the M42 ran great in the donor car, test the stuff like the fuel pump, chassis wiring, etc.

If the recipient ran great, test the coolant temp sensor and maybe swap the O2 sensor.
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS

Uniquestrain

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Re: Helpppp 94 m42 swap, troubleshooting
« Reply #2 on: April 25, 2013, 12:55:21 PM »
I bought the motor from someone on craigslist
Rebuilt the head and torqued it down to specs, compression was at around 160 on all cylinders
And no problms at all, just that the oil pans were different but i put my oil pan fom the 91 onto this new engine
Also it doesnt seem like my fuel pump isnt turning on....doesnt smell like gasoline or anything when i crank it and cant hear it turn on
Im leaning more of the broken knock sensor side...
Oh and its the cam sensor thats broken alittle
Sorry bout that

DesktopDave

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Re: Helpppp 94 m42 swap, troubleshooting
« Reply #3 on: April 27, 2013, 10:12:55 AM »
I posted in your other thread.  Sounds like a pretty typical problem - we'll get you running!
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS