jfine

1989 260E, 190,000 miles.

Just in the last few days, all of a sudden, the idle, in neutral or park, is about 1500 RPM. After driving 10-15 miles, I stop, place in neutral, it drops a bit from 1500 to 1200 RPM, but still too high.

In drive, at idle, it will drop to about 900 RPM, but it used to be about 6-700.

I looked at all the vacuum lines, rechecked them again, car runs fine, just the idle.

I'm thinking maybe the Idle Control Valve needs cleaning or replaced. Trouble is, the 2 hoses on each side are of course original, and I'm afraid they might break or split if I try to take them off. Only way to clean is to spray some brakecleen or something in there, right?

On the other hand, someone told me the Idle Control Valve has a breather hose to keep the gunk out of there, unlike most other vehicles. Is this the 2 hoses on either side?

Or, it may just be a sender somewhere going bad, possibly sending the wrong signal to the ICV. I wouldn't know which one, or how to test, but I do have an ohm meter.

Also tracking down a Haynes manual for this thing is near impossible.

Any help is highly appreciated, thanks in advance!

UPDATE: It did it this morning, (I keep it garaged), started up, idle too high, drove to work, which is about 10 miles away. Stopped at work, place in neutral or park, idle too high. After work, started up, idle too high, but, when I pulled into the garage at home, stopped, idle was perfect, everything normal. I dont get it. Something is sticky or intermittant.

jfine

So it's not a cold/hot issue either.

When I got home today, it idled perfect again.

Then, 5 minutes later, I had to go to the store, and it started the cycle again: 1500 RPM at idle, 900 in drive. Then drove to the store and back, never came back down again.

This has got to be a sticky idle control valve?

ps2cho

Pull off the ICV and shoot some carb cleaner in it. It could just be gummed up.

And the obvious make sure no vacuum leaks. To be idling at 1500 though it would have to be one HUGE leak.

jfine

Should I just try and take off the left side hose, and spray cleaner in there? Or do I really need to remove the ICV to get it clean? Pulling off the ICV means taking off both hoses. Man I really don't want to split those hoses as it looks damn near impossible to replace them without pulling the entire throttle assembly off.

ps2cho

Take it completely off. You don't need to take anything else off. Just unplug the rubber vacuum hoses both sides (just unplug, don't pull it completely out from the other end down below the assembly. You don't need to), the 2 bolts, and lift it out. That is it!

If you take off one side, you sure you want all the dirt to go back into the engine when you spray one end? So do it right and take it completely out. Goodluck!

jfine

Thanks for your help, you're right, it needs to come off. I'll do it tomorrow, and keep you posted. Now that it's coming off, I read that someone soaked it in something like 99% rubbing alcohol for 20 minutes, flushed, then again. Is there something inside that may be damaged by a carb cleaner?

jfine

I took off the ICV, cleaned it with carb clean. When I took it off, it really looked pretty clean inside to me. Some dirt came out when spraying, but not much. I can move the little metal door with a small screwdriver easily, and it springs back with no drag, seems smooth and seems to operate normally.

Put it back on, no change. Idle at 14-1500 RPM. After a few minutes, it will gradually drop to about 1200 RPM, but will not completely idle normal unless I drive it around, like 5 or 10 miles.

Then I took the wires off the ICV. Now it idled perfect. But gunning it at idle a few times proved that was not going to work. Not smooth out and back into the idle circuit without those wires, and even a bit of very light backfire. Nope, I put the wires back on, and now I'm back to square one.

Anybody got any ideas?

YNVDIZW124

Change the temp sensor at the back of the engine....

jfine

Hi there are 2 sensors toward the back on top of the head, is it one of these or how to identify? thanks

ps2cho

I would comment and say my engine temp sensor broke (literally I snapped it in half) and it did not show any raised idle rpm issues, just a rough idle only when cold...but then I have the two prong one and not the updated "plug" type. Not sure if it made changes other than reports for error codes.

I would lean towards saying its the same unit just with the extra error handling for code pulling. So IMO I doubt that is the problem part.

To check operation of the ICV, you need to apply a 12V battery to the poles and listen for a "click".
Make sure to check for vacuum leaks and make sure the air flow plate is centered correctly.

jfine

Didnt see a +/- on the ICV, does it matter when I apply battery.

Air flow plate.... is that the moveable plate inside the ICV? I moved like a door inside the ICV with a small screwdriver, but it was not centered from closed to open at resting position, mostly toward closed but not all the way,

jfine

Todays fun:

Started up this morning, idled @ 1500 RPM.

Went to store. Then decided to drive around a bit to see if it would drop. Drive about 5 miles, stopped. Idle still 1500 RPM. Just sat and waited letting it idle, just would not go down. Drove home.

2 hours later, I start it. Idle climbs to 1500. I just let it sit and idle. After the supposed 28 seconds, it started to audibly change speed very slight. Slowly, it drops about 100 RPM. About 10-15 seconds later, slowly drops another 100 or so. Slowly slowly, until, after a few minutes total, it finally drops almost exactly to 1000. Stays there and idles smooth as silk, I mean smooth. I cant believe what I'm seeing and hearing. Put in drive, back in neutral, perfect. So, I shut it off.

About an hour later, I start it, drive to the store again. Still perfect in every way. Spent about an hour or so in the store. Started it, 1500 RPM again. And, all the way home, pulled in garage, would not go down, just sat at 1500.

Wolfe190

This is just a thought, try pulling your fuel pump relay and cleaning the contacts with electrical cleaner. Then apply some dielectric grease to each one. Could help....

You can actually do this with all the sensors/plugs in your engine compartment. You never know - you could get lucky