BMW 318is E36 M42 erratic idle problem

[rangelo]

My BMW 318is E36 M42 has a strange idle problem. Sometimes the engine starts out ok and works at regular RPMs for a while, and sometimes the erratic idle begins ass soon as I start the engine. The idle go up and down from almost stalling to 2000 RPM or so. At that time the Check Engine Light comes on. It goes on for about 30 seconds or so and then it levels up for a while. If I hit the gas pedal the Check Engine Light disappears and the idle levels up for a short time. I disconnected the Idle Control Valve and it seems to help a little. Then the Check Engine Light stays on. And even then if I just watch the RPM gauge there are variations in the idle, but not as bad. As the engine warms up the idle goes from about 850 up to 1200. Could it be a vacuum leak??? O2 sensor??? Temperature sensor??? Any ideas???
Any help will be appreciated.

Rick

 

[SigEp259]

I would think vaccum leak is a possible. Another, as I am new here, is throtlle position sensor (TPS). Another could be a fuel filter clogged.

 

[rangelo]

Thanks SigEp259, appreciate that... I think I'm going to shotgun the problem... I just ordered a new idle control valve, O2 sensor and one knock sensor. I noticed that the plastic casing on the front knock sensor is cracked, probably from over-tighten it. Does anyone know at how much I need to setup the torque wrench when I tight the knock sensor???

Rick

 

[rangelo]

Thanks to all of you for the input... I'm glad I invested in the parts rather than mechanic/diagnostics/code readers... ICV - $117.51, O2 Sensor - $62.71 and knock sensor - $65.43: total of $245.65 online shopping... I spent all weekend working on this issues and it seems like my instincts were right... After replacing the ICV the idle was steady and I thought it was fixed. The RPMs remained steady after warm up, but the check engine light came on again. Same thing - push the gas - it goes away... Next, I replaced the O2 Sensor. Never saw the check engine light again. The sound of the engine, however, still had some "pinging" to it. Gas quality you would say??? Sure enough, after replacing the knock sensor that had the cracked casing, the engine sounds just perfect. Performance wise feels just a little faster and more powerful, but gas mileage/economy went way up...
Considering I did buy this car at a car auction for under $1000, and have already replaced Starter, Front shocks(2), Wheel Baring Hubs, Water Pump, Radiator, Thermostat + housing and battery, the only thing left now is the AC/Heather Blower... that really blows... I hate it already... I actually consider getting rid of my 318... anyone interested??? r_angelo@yahoo.com Body is perfect and tires are new...