Engine Performance problem
1994 BMW 318 4 cyl Two Wheel Drive Manual
when I start up my car it idles between 3500 and 4000. I have replace the mass air flow sensor, throttle positioning sensor, checked for leaks and even disconnected the throttle cable. The car had a fuel leak and it idled at maybe 800. Soon as I fixed the leak the idle when up. I disconnected the negative battery cable to see if the engine would reset itself and still the same is happening. All fuses are good. What should be the next I could do?
Hi BigKuntri_63h, welcome to 2carpros and TY for the donation
Try cleaning out the idle speed control valve and see what happens its job is to target the idle speed at all times.
Also disconnecting the battery could throw off a sensor/s that probably needs relearning such as one the ISCV to relearn the idle speed
July, 18, 2010 AT 7:35 AM
I went back and replaced it and tried disconnecting the battery again and its still doing the same thing. It stayed at 3000 rpm this time. I decided to drive it just to see what it would do. I drove it up the road and it cut off on me. Had no promblem starting back up. Now when I was driving it as long as I was on the gas it would accelerate. Soon as I come off the gas it cuts off. Now with it parked the idle bounces around between 2000 and 3500. Now im thinking that maybe something might be up with my tps. What you think?
July, 18, 2010 AT 7:38 AM
Go ahead and check and test the TPS idle and wide open throttle voltages and get back with the readings
July, 18, 2010 AT 7:43 AM
How do I go about testing the TPS like that. And what type of equipment would I need?
July, 18, 2010 AT 7:44 AM
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may require a relearn procedure after vehicle battery is disconnected. Many vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When vehicle battery is disconnected, this memory is lost. The computer will use default data until new data from each key start is stored. As computer memorizes vehicle operation for each new key start, driveability is restored. Vehicle computers may memorize vehicles operation patterns for 40 of more key starts.
Customers often complain of driveability problems during relearn stage because vehicle acts differently then before being serviced. Depending on type and make of vehicle and how it is equipped, the following complaints (driveability problems) may exist: Harsh Or Poor Shift Quality
Rough Or Unstable Idle
Hesitation Or Stumble
Rich Or Lean Running
Poor Fuel Mileage
These symptoms and complaints should disappear after a number of drive cycles have been memorized. To reduce the possibility of complaints, after any service which requires battery power to be disconnected, vehicle should be road tested.
GENERIC COMPUTER RELEARN PROCEDURES
Some manufacturers identify a specific relearn procedure which will help establish suitable driveability during relearn stage. These procedures are especially important if vehicle is equipped with and electronically controlled automatic transmission or transaxle. Always complete procedure before returning vehicle to customer. The following general procedures are to be used if driveability problems are encountered after power loss or battery has been disconnected. These procedures may provide an aid in eliminating these problems.
Set parking brake, start engine in " P" or " N" position. Warm-up vehicle to normal operating temperature or until cooling fan cycles.
Allow vehicle to idle for one minute in " N" position. Select " D" and allow engine to idle for one minute.
Accelerate at normal throttle position (20-50%) until vehicle shifts into top gear.
Cruise at light to medium throttle.
Decelerate to a stop, allowing vehicle to downshift, and use brakes normally.
Process may be repeated as necessary.
July, 18, 2010 AT 7:47 AM
You need a digital volt/ohm meter DVOM and follow the procedures in the repair manual
July, 18, 2010 AT 7:50 AM
Or you can check its resistances
Throttle Position Sensor (TPS)
Idle Position 3200-4800 ohms
Fuel Load (WOT) Position 800-1200 ohms
July, 18, 2010 AT 11:09 AM
Lack of idle control could be related to the ICV, but it seems there is something else going on here. The crank case vent valve is the first thing I would inspect, check out this link: http://www.realoem.com/bmw/showparts.do?model=CA53&mospid=47490&btnr=11_1408&hg=11&fg=15
#11 is the valve.
August, 11, 2010 AT 5:07 AM
I ended up checkin out everything and come to find out my manifold gasket was sucking alot of air in everytime I started it up. I replaced that and now I have a stedy idle.
August, 11, 2010 AT 7:34 AM
So in the end, the leaks that were " checked out" according to your first post, were what caused the high idle. Being complete is such a wonderful thing Ã