Cold:Low Idle, Wants to Die, Black Smoke - Warm:Runs Excellent

[R3VN R3D]

I drive an '84 325e.

The weirdest issue started yesterday on my way to work. While driving normal, my cars idle dropped and the car died. I got it to start again and pulled off the road. I started the car and it ran fine so I went to work, no problem.

After work when I started the car, it had a surging idle and wanted to die, but didn't. When I would rev the engine, it sounded constricted and had trouble getting to high RPMs and black smoke came out of the exhaust and it smelled like something was burning. Once I let off the gas, the idle would drop and almost die.

I had to get home so I figured if I would 'heel toe' the gas and brake and keep the idle up and just get home.

This is where I am confused. After about ten minutes of driving like this and black smoke coming out of my exhaust, the car started to run good, I mean excellent. It started to have more power and better response than ever before. When I first got the car, the tired engine was missing all of it's power and I accepted that. Now, it ran like a different car, a new e30. Too good to be true.

I hoped it stayed this way, except, when I woke up this morning, it ran like shit again until it warmed up. :???: Any help would be appreciated.

[slo325i]

My car did this when the ICV was unplugged... I guess it was loose??

Try jiggling the ICV plug. Hope it helps.

Justin

[R3VN R3D]

My car did this when the ICV was unplugged... I guess it was loose??

Try jiggling the ICV plug. Hope it helps.

Justin

Thanks. That was the first thing I went for. I had the ICV scoped and adjusted a few months ago so I thought it was unlikely that it would be the ICV. But I unplugged it while the car was running and the idle flew up and dropped back to normal after I plugged it back in. I also opened the screw all the way and it didn't really help matters.

[nando]

coolant temp sensor

[jlevie]

A bad time-temperature switch could allow the cold start valve to operate longer than it should, which would make the engine run very rich.

[R3VN R3D]

coolant temp sensor

Is the Coolant Temp Sensor and Temperature Sending Unit the same thing?
Also, Real OEM says that I have both a Cooling Temp Sensor (Part #62110788115) and a Temperature Switch (Part #12631279722) on my Thermostat Housing but Pelican calls both of these Pat #'s Temperature Sending Units.

http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=11_0759&hg=11&fg=35

http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search.cgi?command=show_part_page&please_wait=N&make=POR&model=BE30&section=WATmis&page=4&bookmark=21&part_number=12-63-1-279-722-M9

A bad time-temperature switch could allow the cold start valve to operate longer than it should, which would make the engine run very rich.

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?please_wait=N&forumid=&threadid=&command=DWsearch&description=13621274630&FILTER_BE30=ON&FILTER_TECH=ON&FILTER_SUPP=ON&FILTER_ACCE=ON&FILTER_CARE=ON&FILTER_STUF=ON&FILTER_PERF=ON&FILTER_MISC=ON&FILTER_GADG=ON&FILTER_TOOL=ON

So how could I determine which of these three things could be the culprit without buying and replacing all three? Although I'm sure it couldn't hurt to replace all three. Thanks for both of your opinions.

[jlevie]

The most likely failures of the temperature sensors are a shorted or open sensor. Of the two, the only one that matters as far as operation of the engine is the one that provides data to the DME. On open CTS would look like a cold engine and a shorted CTS would look like a really hot engine. In either case I doubt that the engine would run well once it is up to temperature.

That leaves the time-temperature sensor as the likely suspect.

[R3VN R3D]

The most likely failures of the temperature sensors are a shorted or open sensor. Of the two, the only one that matters as far as operation of the engine is the one that provides data to the DME. On open CTS would look like a cold engine and a shorted CTS would look like a really hot engine. In either case I doubt that the engine would run well once it is up to temperature.

That leaves the time-temperature sensor as the likely suspect.

Thanks jlevie. Is that #16 in this diagram?

http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=11_0759&hg=11&fg=35

If so, it's kinda pricey. Any way to test the thing before I try to replace it? Thanks again.

[jlevie]

That would be the part. Check the Bentley manual. I don't have mine handy and don't remember if there is a test procedure for that.

[R3VN R3D]

I'll check the Bentley. Weird thing is, problem went away. I did nothing yet and now the car runs fine, for now. I can only assume it will happen again. What would make a problem come and go like this? A Loose Electrical Connection or Ground?

[zed933]

i'm having the same exact problem only thing is mine is an 89 325i

[dmwe30]

what would cause the i to have this problem ive already replaced the cts no black cloud or anything but deff rich its probably just my iacv being a jerk

[hotballs]

I'm also having the same issue on my 84 325e. The coolant temp sensor is where I'm starting. I'll let you know if I have any luck.

[Aviator]

coolant temp sensor

Where is this located? My car runs like crap as well cold. I recently changed the fuel pressure regulator and cold start valve, but that didn't fix the problem.

[hotballs]