I have a 1991 740 non turbo with ~233,000 miles. The other night I tried to drive somewhere but at every stop sign/light my engine would die. Here is what is going on as of today:

I can start the car and it seems to run fine, but idle is higher than it used to be at around 1100 rpms (cold or hot operating temp). If I do not touch the throttle the car would run forever. If I so much as blip the throttle (especially after its warmed up) the engine will rev and then drop rpms until it dies (which takes about 2 seconds).

Things I have checked or done:

Cap and rotor (pulled and cleaned, looked to be in new condition)
Plug wires
Spark plugs
Air filter
Cleaned IAC
Throttle body is clean
Flame trap was removed all together, all hoses cleaned (about 2 weeks ago)
Checked for vacuum leaks with carb cleaner
Oil and filter are fresh
Coolant is fresh

checked for engine codes using the OBD black box under the hood, nothing was logged

I filled up with a full tank of gas about 2 weeks ago, and added techron to the tank- now my tank is almost empty (averaging about 16-17mpg so far)

This problem did occur about 2 days after getting about 3 inches of rain. Driver's side floor is soaked. Passenger's is dry.


I suspect the fuel filter, coolant temp sensor or the IAC. What do you think?

 

Make sure the TPS is operating/adjusted and/or that the plug connecting to the TPS is intact and corrosion free. My 91 940SE had the same problem, broken wire in the plug connector to the TPS.

 

The thought occured to me while I was spraying fuel injector cleaner into the throttle body. What happens if I unplug the electrical connection to the IAC while the engine is running?

With the IAC unplugged engine idles perfectly at around 1000 rpms. I can rev it all I want and it wont die. Drives fine.

What happens when I plug the IAC back in? It runs like **** and dies/revs to 2000 rpm.

Is it alright to drive around without the IAC for a while until I can get my hands on a new one?

 

anybody? anybody? bueller?

 

I have a 1990 740 turbo, runs great down the road, but dies when I pull up to stoplights.

voltmeter struggles when I first start it up although I have replaced the battery and the alternator tests good

I replaced the in tank fuel pump when I first bought it 6 months ago

Could this be fuel filter? Inline fuel pump? IAC?