Ok. This is a long one. I recently purchased an 87 325es. The car was originally an e swapped to an i and auto swapped to manual. The idle is alittle on the high side (about 1050 hot and cold). I also noticed that when the car warms up if i blip the throttle up and let it fall to idle the idle will fall to about 800 and the oil pressure light will flicker and then jump back up to 1050 and the oil pressure light will go off. at first i took attempted to diagnosis these 2 symptoms as 2 different problems.
So at first i replaced the oil pressure sensor, no difference. Then i removed the oil pump and found it to be scratched and gouged on the inside, i assumed this would fix the oil pressure problem which it did not. while i was in there i removed 2 rod bearin caps and found nothing odd. i replaced the oil and filter with 15 40. so then i installed an oil pressure guage to verify a correct reading. with the engine ice cold i had a reading of 50 psi, as it warmed up it fell to about 11 psi, then i blipped the trottle and watched the oil pressure. as the idle increased the oil pressure went up to about 25 psi and as the idle dropped to about 800rpm the pressure fell to about 7 psi and then when the idle settled at 1050 the pressure stablized at 11 psi again. this made me beleive that my oil pressure idiot light was correct.
So after having no luck fixing the oil pressure issue i decided to attempted the idle issue in hope that the idle was actually causing the oil pressure problem. I was thinking that maybe the car is almost stalling out when coming off rev which was making the oil pressure light come on and when it was about to stall out the car attempted to bump up the idle to keep it running. SOOO, i smoke tested the intake and found no leaks anywhere. after that i removed the ICV and cleaned it, no change. I checked and adjusted the TPS, now the real weird thing is that when i adjust the idle screw all the way out the idle continues to stay at 1000 rpm. At this point i was stumped, i decided to buy some test parts, I swapped in a new dme, throttle body and tps, icv, and mass air flow meter. STILL no fix.
I decided to search the bentley for answers. I checked the coolant temp switch and sensor. and checked the wiring to the tps and icv. now the bentley says that when the ignition is on measuring across the middle pin and each outter pin on the icv connector i should have 10v, which i do not. measuring accross the middle wire and the white and yellow outter wire i found only 4 volts. I checke volatge at the dme and have only 4 volts there too. Not sure if this is the problem or not but dont know where to go from here. Im stumped and on the verge of saying its un-fixable. PLease, if anybody has any suggestions or ideas, im all ears. thanks, matt
So at first i replaced the oil pressure sensor, no difference. Then i removed the oil pump and found it to be scratched and gouged on the inside, i assumed this would fix the oil pressure problem which it did not. while i was in there i removed 2 rod bearin caps and found nothing odd. i replaced the oil and filter with 15 40. so then i installed an oil pressure guage to verify a correct reading. with the engine ice cold i had a reading of 50 psi, as it warmed up it fell to about 11 psi, then i blipped the trottle and watched the oil pressure. as the idle increased the oil pressure went up to about 25 psi and as the idle dropped to about 800rpm the pressure fell to about 7 psi and then when the idle settled at 1050 the pressure stablized at 11 psi again. this made me beleive that my oil pressure idiot light was correct.
So after having no luck fixing the oil pressure issue i decided to attempted the idle issue in hope that the idle was actually causing the oil pressure problem. I was thinking that maybe the car is almost stalling out when coming off rev which was making the oil pressure light come on and when it was about to stall out the car attempted to bump up the idle to keep it running. SOOO, i smoke tested the intake and found no leaks anywhere. after that i removed the ICV and cleaned it, no change. I checked and adjusted the TPS, now the real weird thing is that when i adjust the idle screw all the way out the idle continues to stay at 1000 rpm. At this point i was stumped, i decided to buy some test parts, I swapped in a new dme, throttle body and tps, icv, and mass air flow meter. STILL no fix.
I decided to search the bentley for answers. I checked the coolant temp switch and sensor. and checked the wiring to the tps and icv. now the bentley says that when the ignition is on measuring across the middle pin and each outter pin on the icv connector i should have 10v, which i do not. measuring accross the middle wire and the white and yellow outter wire i found only 4 volts. I checke volatge at the dme and have only 4 volts there too. Not sure if this is the problem or not but dont know where to go from here. Im stumped and on the verge of saying its un-fixable. PLease, if anybody has any suggestions or ideas, im all ears. thanks, matt
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