Is my Idle Control Valve about to die?

[George Davis]

'94 525i automatic. Yesterday, while stopped at a light, the car surged three or four times, as if I were holding the brakes on and giving it a little gas (in gear). But I wasn't giving it any gas, so I assume the ICV was doing it.

Only happened once, behavior has been normal since then. Is this a hint that I should be buying a new ICV, or is occassional ICV weirdness normal?

Thanks for any info!

[SRR2]

'94 525i automatic. Yesterday, while stopped at a light, the car surged three or four times, as if I were holding the brakes on and giving it a little gas (in gear). But I wasn't giving it any gas, so I assume the ICV was doing it.

Only happened once, behavior has been normal since then. Is this a hint that I should be buying a new ICV, or is occassional ICV weirdness normal?

I've been pursuing similar kinds of weirdness in my '89 535 manual. Idle out of control, intermittent and unpredictable fuel cutoff above 1500 RPM. I've checked nearly everything in the FI system and have found no obvious smoking gun. There is no error code from the "stomp test". I even pulled out the ICV and cleaned it with some small improvement. So it looks like either the ICV has intermittent failures/hangups as it heats up, and or the ECU is giving it improper commands. I'm going to give the benefit of the doubt to the ECU since it comes up clean in the self-test and take the plunge with a new ICV. I should know within a week when I get the new ICV whether my diagnosis was correct. That might give you a datapoint on your problem.

As a minimum, try taking your ICV out and cleaning it. It's a 10 minute job. I took Saran wrap and blocked off one nipple, poured in a little Gumout, and then capped off the other nipple with Saran wrap. Shook it around a while, including some rotation around its axis. It looked pristine clean afterward and seemed to rotate freely, but my problem was only somewhat improved.

[Denasti]

I have a similar problem. last week when I went to accelerate the engine would miss hard every 2 seconds like the key was being shut off but ran normally when starting and cruising under 2k RPM.

Well that faded a bit but now at Idle it misses every two seconds and sometimes during acceleration. This happens whether its warmed up or cold.

I have seen others recomend wires,coil,cap,rotor,fuel filter,pressure regulator or vacuum boot replacement but thats alot of crap to through at a problem. :( I recently did a head rebuild and replaced all that stuff short of electrical components but my car did sit for about 18 months and maybe that new filter is stuffed with crap again.

[Javier]

it rises RPM, but it may have received an order from DME to do so. You are not describing hesitation followed by rpm rising, so If I would guess, I 'd say there is something telling false info to DME, causing DME to open ICV.

CPS, Air flow, Temp, no idea, may be some Motronic expert can tell.

Javier

[genphreak]

it rises RPM, but it may have received an order from DME to do so. You are not describing hesitation followed by rpm rising, so If I would guess, I 'd say there is something telling false info to DME, causing DME to open ICV.

CPS, Air flow, Temp, no idea, may be some Motronic expert can tell.

Javier

I'd second that.... cleaning the ICV (if it is dirty) will help it respond quicker to balance out the problems being created elsewhere... ;)

But if you did the head or had it done (properly) it shouldn't need this!

Always keep your ICV clean though, it'll last longer. I've never had trouble using throttle body sprays (carb cleaner) on mine... wouldn't hurt to do a thorough check- Valve adjustment/intake manifold leak, AFM pipes, vacuum hoses, spark plug gap, coolant sensors (I had this problem once, it turned out to be a coolant sensor), crankshaft sensors- make sure you check for error codes on the ECU.

And of course, when were your injectors last cleaned?? However I think a most likely culprit could be the O2 sensor. If you aren't already aware, coolant kills o2 sensors. if your head was replaced and coolant could possibly have got into the exhaust.. ages ago and therein cause early onset of 02 failiure. As such the 02 sensor will be feeding bad data to the ECU and upsetting things especially after combustion conditions change. (Stop/start driving)

And since you recently did the head, do some **paranoid** checks for coolant leaking into the exhaust JIC the **new gasket** is leaking... it can happen.

:) GP