Engine stuttering, unstable idle... i finally have a chance to mess with it

[whitey_E30]

heres exactly how it works.....

i turn the key and the car cranks about 2 or 3 times and starts up just fine. if i put my foot on the gas real quickly and rev it up to about 4 grand and take my foot off the gas, the car calmly roars it engine then quiets down, just like it should. i put the car in reverse and the rpm's drop slightly from about 1100 to 900. at this point, the car starts a chugging sensations followed by and uneven idle. sometimes it drops so low it eventually stalls. this only happenes when i take my foot off the gas in order to hit the brake to shift into drive. once in drive, the idle then jumps to 1100 rpm and stays fairly even. at this point in drive, if i attempt to speed up quickly with the gas pedal then take my foot off and hit the brakes, the rpm drop extremly low and sometimes stalls the car. HOWEVER, none of these symptoms happen if i let the car warm up for about 10 minutes. this is strictly from a cold start.

when i do eventually get on the road, the engine stutters immensly. almost like i am driveing in really strong wind gusts. this happes around mid throttle to three quarters on the way open. i can let up on the gas and slowly apply pressure and that seems to help. for a few seconds anyway. then the stuttering returns until the cars engine is warm. one other thing I have noticed is that the pedal seems dead from around a quarter of the way down to three quarters of the way down while the car is stuttering. the only respons i can get is when i push the pedal to the floor. then the car takes off like a bullet.

another thing is my fuel economy has dropped from about 27 mpg to 20.

i just ran a continuity test on the tps. (i think i did it right) i was told it was the switch underneath the accordion hose comeing from the air filter. it plugs right into the throttle body. i unplugged it while the car was running, my rpms dropped for a second then rose up to about 1200 or 1300. between the middle pin and the outside pin i got a reading. the same for the other side. there was about of oil and dirt that seeped down near the switch to i attempted to clean it out. I aready repleaced the icm and icv. im heading into town right now to get some starting fluid to spray on the hoses to check for cracks.

spark plugs.

[saltshaker185]

whens the last time you did basic matenience? and how long have you had the car?? last time you changed the fluids and o2 sensor?

[Numark318i]

K. since its anE30, its atleast 10 years old....haha. anyways, its gettting old, and judging by the fact that your Idle is to high(should be at like 600, maybe 700) you prolly have vacuum line leaks. G to realoem.com and look up your car, and find all the vacuum lines.


I changed out all mine in my 1991 318, made a huge difference. If not that then check you O2 sensor. Also it might be the temperature sensor?

also is your car throwing any codes?

[Starmavin]

You should have conituity between one of the outside ones at closed throttle and then the other at wide open throttle, but never both at the same time. Unless I didn't get that right from what you said.

Also, use a voltmeter between pins 7 and 4 of your idle control box connector. You should get battery voltage with gear selector in Neutral and Park positions, no voltage in other positions.

[kenika65]

Hello, I had the same problem with my idle in my 1991 m42 318is to where i was driving with my foot on the gas at all times... then i checked all vacuum lines and replaced a few but still had the idle problem then i noticed that the rubber air intake had a crack in it so i took it off to notice it had a large crack or hole so i replaced with new and now no problems.... if any help