Motronic Cold Idle Solved (for me anyway)

[dentist90]

Me and a few others have posted problems with a sensitive loping idle when engine cold on our 3.2 Motronics. Yesterday I cleaned the ICV with carb cleaner and reinstalled it. Things went from bad to worse as the idle bounced up and down from 1100 to 600 and wouldn't settle. Just to play around I reinstalled the valve UPSIDE DOWN, with the arrow pointing up to the air cleaner side. Presto-Chango!! The car starts perfectly when cold now (~1100rpm) and doesn't threaten to stall when I touch the accelerator. After a minute the idle slowly settles down to it's familiar old 800rpm.
Q: Is this ICValve upside down NOW, or was it upside down before?

The arrow is on the back side pointing up. Would someone else mind taking a look at their engines and seeing which way their ICV is installed. There's no arguing with the results here!!!

[ZOA NOM]

It is definitely upside down now. I would swap it back to see if the problem repeats. If so, I would investigate further before driving the car that way. It seems that something is amiss elsewhere.

edit: I wonder, did you take it apart completely when you cleaned it, and put something backwards on reassembly?

[jbrinkley]

facing front, arrow down on mine

[dentist90]

Nope- didn't crack it open. Just sprayed into the orifices and shook the valve around to make sure it was free moving. Checked with the ignition key on and it was humming and the valve inside was 1/2 open and pulsing a bit. This makes no sense to me either! I guess this a good time to ask if any harm can come of it?

[ZOA NOM]

I dunno if it can harm. The valve seems to perform the same function in either direction, so I can't really see why it would work better in one way vs the other. I'm looking through the Bentley now.

[Hendog]

Facing front, arrow down on mine as well.

[ZOA NOM]

I wonder about the electrical connection. Could there be an intermittent connection that makes when you turn the wire over?

[dentist90]

Just flipped back right way (arrow down again) and it seems fine today. Yesterday it loped and sounded just terrible. Car is warm now, so I'll have to wait until tonight or tomorrow am to see how it starts cold. Electrical connections seem fine... servomotor buzzes when ignition on and valve moves freely. Weird. Perhaps there was a bit of residual carb cleaner trapped in the body that got sucked out when the car started (vacuum applied). I did take the car for a 5 min run after first installing the freshly cleaned ICV and that did not clear things up, but the instant I put it in upside down it was music. Resistance across the valve terminals is as per Bentley, so I'm sure the valve is working. As a matter of fact, it must be doing something because when I turn on the AC compressor the idle stays nice and smooth at 800. At least I'm getting somewhere. I'll post tomorrow to let you know how it starts cold.

[ianc]

I also can't see why there should be a difference in which direction the valve is installed. My guess is that when you reinstalled it the first time, you had the hoses pinched in some strange way that caused a vacuum leak. Just my .02,

ianc

[dentist90]

Makes no sense to me, either. My money is on carb cleaner still inside the housing. Those hoses are pretty beefy, and they were clamped each time. The difference was instantaneous though. I can't understand how a 5min drive wouldn't clear it out but flipping it over fixed it immediately. That's why I posted the pictures... just in case it was upside down to begin with. The thing is in normally right now and it drives fine. I'll post tomorrow after I get home from work. A cold start tomorrow should confirm things. Thanks for your 2cents... I'll give you your change tomorrow.

[Nine9six]

I'm with ZOANAS on this one...The rest just doesnt make sense. Have you tried installing a buddy's ICV, to see how it reacts? How about a used one?

[dentist90]

Well I started it up this am with valve in properly and it was fine. Ran at 1100rpm and I could blip the throttle without it loping and threatening to stall. After a minute or two it settled down to 800 rpm... perfect. I wiggled the harness and wire lead and no change. Kept humming and idle didn't budge. Obviously there was a problem with the valve being a bit dirty inside as it never idled cold at 1100 before... started at 800 and couldn't even think about the throttle without it loping down to near stall. I never had a problem with the idle after warm, only when first started. The mystery as to why it suddenly ran so well upside down will probably stay a mystery, but I'm happy that I can now start it up and drive away without being bucked out of my seat!

[ianc]

Maybe there was some bit of gook in there that got loosened by your cleaning but couldn't get past the valve and turning the ICV upside down thus reversing the flow allowed it to get sucked into the intake?

ianc

[johnnyo]

It may be possible your connector had a build up causing bad continuity and by simply pulling off the connector to remove and spray valve then installing then removing again to flip it over abraided the conection and giving better continuity at the connector,

[Asjac]

I am wondering if this may fix my problem that sounds the same as yours. It has just occured since I swapped ignition wires. When I was installing them, I found a loose wire and plugged it in as I thought I had just un-plugged it. That wire was the O2 sensor. I replaced and it didn't fix it, I thought it did, but now it has returned.

Have you replaced your O2 sensor enroute to finding this?

Edit: Will try cleaning this part tomorrow, it is on top of the intake manifold correct?

[dentist90]

Asjac... O2 sensor didn't seem like the problem here. Idle was only very touchy when cold. Once the car was warm there was no problem. I believe the Motronic brain ignores O2 sensor input until Head Temp sensor indicates that the car is warmed up, so O2 sensor should not be a factor at startup. Yes, the Idle Control Valve is right in the middle of the engine bay behind the fan housing, in front of intake manifold crossover -takes literally 3 mins to remove.
Good luck

[john4061]

Dentist90: When you started your car did it also smell like it was running rich, unburned gas smell? Mine has the same idle problem as you described plus the running rich problem.

( By cleaning out my idle valve as you did and replacing my O2 sensor I am hoping to take care of both problems.) Do you think that these steps will cure the running rich at start up problem also?

[dentist90]

john4061... never smelled rich, except right after I cleaned it and first reinstalled it. The car was warm by then but the idle was jumping between 1100 and 800 and I could smell it. It was running really badly and I thought I might have buggered something up with the carb spray, but that issue has resolved. I would strongly suggest that you clean the ICV (it is so easy to do). The little piston inside should be able to rotate freely from open to closed when you spin it. I think mine was stuck about 1/2 way open... wasn't responding quickly enough to maintain a smooth idle. At start you probably want a bit richer mixture. If yours is stuck in a more closed position it could lead to air starvation, hence a rich mixture even when warm and a weak idle? I have heard other people recommend alcohol to clean it, but I find spray carb cleaner removes gum and varnish so much quicker and it evaporates pretty fast. Good luck, hope it helps! If all else fails, put it on upside down

[Asjac]

Is it a Motronic thing or is it mine? Whenever I blip the throttle or rev it a little and as comes down it will hiccup and go low on RPM and then come back up to 1100. It also twitches the motor when it hiccups. Any ideas?

[ThePointman]

Facing front, arrow down on mine as well.

Derek have you tried reinstalling the ICV with the arrow down since the problem disappeared?