E21 m50 swap not running good

[ak-]

i unplugged the maf while idling and it made it idle a lil rougher. i have driven it a couple times, up to 2k rpms it runs rough then it literally snaps out of it and seems to run great. like in first gear barely on the throttle it kinda jerks and doesnt run good then around 2k it snaps right out of it ya know.

Not sure if anyone mentioned it because I don't feel like reading, but this sounds like your fuel pump.

I once was putting only $5's into my gas tank for 2 weeks straight to keep it from running out of gas and one day, stupidly, I let it run out of gas..
Since then, it would hesitate below 2rpm and jerk on take offs although everything seems fine above that; pulls strong.
So yea, your fuel pump is taking a shit on you.

Goodluck though. Really cool swap.

[jbxblitz]

i have the same problem on my 318i m50 swap... i dunno what it is either. but then again, i haven't used the right temp sender. i heard we have to use the temp sender from the M10.

also how did you get your rpm gauge to work? im having trouble figuring that part out too..

[jeds320i]

Not sure if anyone mentioned it because I don't feel like reading, but this sounds like your fuel pump.

I once was putting only $5's into my gas tank for 2 weeks straight to keep it from running out of gas and one day, stupidly, I let it run out of gas..
Since then, it would hesitate below 2rpm and jerk on take offs although everything seems fine above that; pulls strong.
So yea, your fuel pump is taking a shit on you.

Goodluck though. Really cool swap.

its a new fuel pump.. well like one year old i guess.. seems to work fine. and i am using the m10 temp sensor. but maybe i took out the wrong one in the m50 and so the computer isnt getting a signal and so its making it run funny? thats what i need to find out. which temp sensor is for the ecu? front or rear one? also im running an aftermarket tach bc the stock 4cyl one isnt calibrated for 6 cylinders.

[derrith]

I described to you what the ecu temp sensor looks like. It's normally got a blue or clear plastic connector on the sensor and has two pins.

Have you hooked up the check engine light? That will give you an idea of what's wrong.

[jeds320i]

both temp sensors have 2 pins, all i need to know is which one is for the ecu(front or back)

[derrith]

They're not always in the front or the rear, especially since you may have removed the wrong one.

What color are the tops of the two temp sensors and have you tried to ohm them out as I previously suggested?

[jrdeamicis]

Im going with crank position sensor. The VR sensor relies on speed for amount of amplification. @ 2k is prob its happy range to start working again right.

And seriously, most important sensor on the car. Replace it.

And, the blue topped sensor is for the ECU. If I remember correctly it lives in the front spot. The brown topped single pin sensor is for the cluster.

[jeds320i]

ok dudes, the temp sensor i replaced with my m10 one was the rear one. it is a black 2 pin. the front one is a blue 2 pin. so im pretty sure i took out the right one. i also got all new vacuum lines on. the small one going to the fuel rail was all crappy looking and i thought for sure it was gonna fix the problem but it didnt. and the crank sensor is new and i verified it was good. i did not check the ohms on the ecu temp sensor yet, but i doubt its the problem.. i guess it could be. im getting quite aggrevated bc i cant figure out whats wrong! it like hunts for the idle like and jerks/hesistates below 2k rpms in gear. it seems to run fine above 2k tho.. i need some help :(

[jeds320i]

BUMP. ive been told maybe im not getting enough fuel pressure? i dont have any type of guage, how can i test it? A guy that already did a m50/E21 swap said the stock fuel pump works fine bc the mechanical fuel injection for the m10 needs alot of volume of fuel. doesnt volume equate into more pressure in a smaller place like the fuel rail? maybe im just not getting enough fuel..?

[jeds320i]

i checked the ohms of the temp sensor and it was at like 3.5 ohms.. and then i checked the other temp sensor that i took out to use my m10 one, and the one was 9 ohms.. so am i running the right temp sensor and is it working properly?