Horrible Idle, Good Idle, Horrible Idle, Good Idle

[BMW BMXER]

My car's stupid.

It will idle fine one light. Then like SHIT the next. Going from 500 to 100 and back and forth. Occasionaly it will die. If I rev it it stops.

If the idles fine and I rev it it won't hold an idle.

While fluctuation the MPG gauge goes back and forth with the surges from 0 to 40 and so forth.

Is it a vacum leak. If so what is the easiest way to find a vacum leak and were are the trouble spots to look. I reckon I should fix this.

Note: Cold weather makes it worse

[Jordan]

swap in another ICV and see what happens.

[lowslowe30]

Had the same problem with my eta and it turned out to be the afm. The small flap was being restricted and not allowing enough air into the engine. When i revved it my car would be alright, but when sitting at lights it would fluctuate and die every once and a while. Mine was also worse in colder weather.

[Jb325is]

had the same problem with the e28, it ended up being the Fuel Pressure Regulator. Check the three things mentioned and one of them will be your problem.

[BMW BMXER]

Ill start with the one first posted and work down lol.

[Sean]

SO, how could I go about testing/fixing my afm?

I have some pretty rough cold starts, and some hesitation during normal acceleration. After warming it, the car won't die at stop lights though.

[arnib]

swap in another ICV and see what happens.

I'll second that.

I took my ICV out a few days ago and cleaned it up inside.
My car is like NEW now, better starting and idle!

:)

[rward325]

I'm going to throw a mokey wrench in the works here guys. I had the same problem, at least it started out that way. Then it got progresssively worse over the course of about a week. I checked all of the above as it made sense to do so. It ended up being a fried ECU and a bad set of plug wires. So, if none of the above works check this out.

[EtaSport]

I am having a similar problem on my car. I check the fuel pressure regulator, i swapped in another throttle position sensor, i installed a new fuel pump, and everything else either is working or was checked. Now, this car had a new ecu installed for this same problem several years ago; probably early 90s. Well, my dad seems to think that the ecu is bad again. tell me if your symptoms were like these...

very bad idle, car wont start sometimes, horrible fuel milage, car jerks in gear, engine dies approaching stoplights, and mpg gauge is always reading 15mpg or less.

if these are similar then I am going to bite the bullet and get the ecu. Thanks guys

Jon

[BMW BMXER]

Nah mines not that bad.

-Stars fine
-No hesitation
-Very rare stalls

[rward325]

Buy the ECU. That sounds like my car a few weeks ago. Does the Check engine light come a lot also?

[BMW BMXER]

Mine? No.