Hi folks,

On my 1990 740 turbo wagon I have been noticing a low idle. It has been idling at about 600 rpms. It has done that for about a month. It dropped from about 700 or 800 which I think is the right idle for these cars.

Anyway, last night the idle just fell off. It will not stay idled. If I don't put my foot on the gas the idles will drop below 500 and dip all the way until it dies.

What do you goes think could cause this? The battery and alternator are good it seems. I was thinking maybe general tuneup stuff. But I was also thinking maybe MAF sensor.

I forgot to mention... the car will drive as long as I keep foot on gas. Say if I drive it around the block and let it idle on it's own it will idle rough then die.

Any thoughts?

Can't I test to see if it is MAF by disconnecting the sensor wire and if it idles normal than I know the MAF is bad?

Thanks,

 

cleaned the throttle body?

 

Good idea... I am going to try that. I hear that is a common issue and will cause a rough idle.

 

replace your idle-air control motor. that could be the issue.

 

I followed the IPD instructions on cleaning the throttle body. It now will idle without stalling out. It is idling at about 750 rpm. When I took the throttle body off the car cleaned it and did the adjustment on the throttle position switch I could hear the two clicks. One when opening the throttle and the other when closing the throttle. However, when I hooked it back up now i am only hearing one click. I think I need to mess with the adjuster screw to give the throttle more room to open and close. Although it is maintaining an idle without dieing it is still a little rough. Anyone else experience something similar?

 

This is my question, is it possible to adjust the throttle position switch with it hooked up to the car? Or, do I need to remove the throttle body and play with the adjustment that way? It is hooked up to the car now and I don't want to remove throttle body to mess with that adjustment.

 

in reality, to find the answere to this question, you need to understand the function of the throttle position switch and the throlle-plate's positioning. it's pretty easy to remove the throttle-body.

three main points of adjustment are the two at the connecting arm that connects the throttle-cable pulley to the trottle-body actuator arm. the third is the stop screw that the actuator arm rests on. and, generally, governs the on/off position for the correct orientation for the switch. i sat gernerally because the fourth adjustment point would be the switch itself.

to answere your question, yes you could do the adjustments with the throttle-body attached. in theory.

 

I guess this question would be better answered by me just going out and trying the adjustments. What I am going to try and do is move the screw so that the arm has more freedom of movement. And my hope is that it will allow the butterfly to close all the way thus allowing the switch to tell the ecu that it is time to idle.

I was trying to avoid removing the throttle body again. It's a pretty simple deal now that I have had it off once. The top bolt on the right by the switch was a pain. I ended up loosing up the switch to give me more room to put a wrench on that bolt. The other issue was removing the vac lines. I sprayed a little pb blaster on them and that helped remove them.