95 740i Check Engine light
Hello everyone! New to the forums here and new to BMW. I bought a 95 740i in april and love the car. I have an issue with it though.
I first noticed it is running rich. The car can run for several hours and not have a problem. Then out of nowhere it will start running rough and die. It will start again but run terrible with the check engine light on. Now if I rev it up above 2000 rpm the check engine light will go out. When I let it idle the check engine light will come back on and run rough.
I have cleaned the idle control valve, mass airflow sensor, and checked for possible vac leaks but have found none.
I can let it sit for a few days and the car will start and run fine for about 5 or so hours. Then back to the same again. Today it runs with no check engine light on, but has some rough acceleration but seems fine at a running rpm of around 2000 or higher. When drop to idle it will run rough but no check engine light yet. I have noticed on occasion that from idle I can rev quickly but get slight hesitation and a little pop, like the timing is off.
I have done the stomp test and it comes back as lambada sensor, but that just seems a general test and could be any one of multiple things causing that.
I do have some white smoke at start up but then goes away. Probably due to a head gasket.
I have replaced the spark plugs also. I don't run premium gas in it, if that would make a difference.
Any thoughts on what this might be would be appreciated.
Last edited by suream; 07-28-2010 at 11:20 PM.