1996 m44 dasc TROUBLE
 

hello all, name is zack and havent been around in a while.
my 1996 318is m44 supercharged bmw has three check engine codes that i cannot fix. 1- random multiple misfire 2- cylinder two misfire 3- cylinder three misfire. on my boost gauge i am reading between 15-17.5 inches of helium at idle, believe a healthy engine SHOULD be approx 20.

i have taken multiple steps to try to fix the problem:
1- new coil pack
2- new spark plugs
3- new spark plug wires
4- new throttle position sensor
5- cleaned idle air speed control valve
6- checked for vacuum leaks.
7- replaced air injection hoses.
8- warm and cold compression test= never below 192 on ANY cylinder

sometimes when i go from in gear to rolling in neutral the rpm's will bounce before maintaining a steady idle speed. (the vacuum pressure bounces with the idle)

i BELIEVE that the misfires occur at low rpm's and thus it holds back off the line and then kinda kicks itself to a stable power curve.

all in all... the car ran a 15.6 on the 1/4 mile (before a few of the fixes) and i spun all the way through first gear. car is drivable but definately holds back.
please help me becaue i am out of ideas.:confused:

You have a vacuum leak. Probably somewhere on the intake.

1+, also remember check the gauge hose for vacuum leak

what are the techniques for finding a vacuum leak?

I use this method:

Start the car and let it idle. Spray carb and choke cleaner around all your intake pieces. If the idle fluctuates, then you know where the leak is.

Or you could just pull everything off before the elbow and reinstall it, making sure all clamps are tight.

Check the hose between the rubber intake elbow and the injectors.

I show 15-17 in.hg. at idle on my boost gauge.

i also read the same numbers, but i use water to test the vacuum leak because the car claner is flamable...