Someday I'll learn. I was driving in a major thunderstorm last night and hit a flooded section of road. I ran through about a foot of water at ~30 mph. Big splash, car goes dead. Won't restart. Wont even crank. Battery appears dead.

A hour later, water recedes. AAA guy comes and gives me a jump start. Car starts fine and I drive it home.

Now, this morning I went start the car and it seems fine at first. But after a few minutes the idle speed starts creeping upwards. It's now idling at about 3000 RPM. I also notice a faint smell of burnt electronics but I can't figure out where it's coming from.

Any ideas?
--
Greg P. 1988 240 DL 'Olga' 170,000 miles

FIRST - check the air filter. Is it wet? A lot? Enough water through the intake can blow the engine. Since you could start it, you may be OK. Mine, after a similar experience, was damp for the bottom 1/3.

Second - be aware of wheel bearing damage.

Third - the idle problem. The idle speed is controlled by the IAC, Idle Air Control. It's controlled by the ECU, which reads engine speed and tells the IAC how much air to allow through.

BUT - the IAC is not even in the loop when the throttle is opened just a little. The throttle position switch is what tells the ECU to kick in the IAC for idle control.

Something in that system has quit working.

Try this: Engine idling at whatever speed, use a large pair of pliers to gradually close off one if the hoses to the IAC. The idle speed should drop, and if you close the hose entirely the engine will die.

If you get that result, it is the IAC system that's at fault.

Engine off, use an ohmmeter to check for continuity between all the pairs of contacts on the IAC. I thinks your model has three wires, check 3 pairs.

An open pair = dead IAC. All oK? Listen closely at the TPS as you open the throttle, can you hear the switch trip?

Beyond that all, you may have water in the harness somewhere, or something else entirely.

The ignition control module, ICM, is near the windshield washer fluid reservoir, look for water there - but that might not affect idle speed. The ECU is in the cabin - and if water rises to its level you will be afloat in an economically totalled car.

Good Luck,

Bob

:>)

FIRST - check the air filter. Is it wet? A lot? Enough water through the intake can blow the engine. Since you could start it, you may be OK. Mine, after a similar experience, was damp for the bottom 1/3.

Second - be aware of wheel bearing damage.

Third - the idle problem. The idle speed is controlled by the IAC, Idle Air Control. It's controlled by the ECU, which reads engine speed and tells the IAC how much air to allow through.

BUT - the IAC is not even in the loop when the throttle is opened just a little. The throttle position switch is what tells the ECU to kick in the IAC for idle control.

Something in that system has quit working.

Try this: Engine idling at whatever speed, use a large pair of pliers to gradually close off one if the hoses to the IAC. The idle speed should drop, and if you close the hose entirely the engine will die.

If you get that result, it is the IAC system that's at fault.

Engine off, use an ohmmeter to check for continuity between all the pairs of contacts on the IAC. I thinks your model has three wires, check 3 pairs.

An open pair = dead IAC. All oK? Listen closely at the TPS as you open the throttle, can you hear the switch trip?

Beyond that all, you may have water in the harness somewhere, or something else entirely.

The ignition control module, ICM, is near the windshield washer fluid reservoir, look for water there - but that might not affect idle speed. The ECU is in the cabin - and if water rises to its level you will be afloat in an economically totalled car.

Good Luck,

Bob

:>)

Thanks for the good suggestions. I think I'm getting closer to the problem but still not there yet.


"FIRST - check the air filter."

The filter was sopping wet. I put it on the sneaker rack in the clothes dryer for about an hour and it seems ok now.


"Second - be aware of wheel bearing damage."

Hmmm good idea. I'll have to give them a look see.


"Third - the idle problem."

"Something in that system has quit working."

Yes I'm sure of that now, but having trouble figuring out what. This is my big problem right now.



"Try this: Engine idling at whatever speed, use a large pair of pliers to gradually close off one if the hoses to the IAC. The idle speed should drop, and if you close the hose entirely the engine will die."

I assume you mean one of the two lines that go in the top? I tried that and it had no affect.


"Engine off, use an ohmmeter to check for continuity between all the pairs of contacts on the IAC. I thinks your model has three wires, check 3 pairs."

I have approx 24 ohms between the either striped wire and the brown (gnd) wire. 48 ohms between the two striped wires. I can hear the click of the switch ok too.

When I goose the throttle and let go, the idle drops back to normal for a second, then creeps back up to 3000 RPM within a few seconds. Somehow, it seems like the ECU thiks the RPMs are too low and is tying to raise the idle. Any idea how the ECU determines RPM?

Any other more things I can look for? I'm searching for my blue book now. I must have put it somewhere but I can't remember where. This isnt how I wanted to spend my saturday. Oh well.

Thanks




--
Greg P. 1988 240 DL 'Olga' 170,000 miles

In an attempt to get closer to the problem, I pinched off the large hose that hose into the IAC from the air valve and voila, the engine idles normally.

Seeing that, I unplugged the connector on the air valve and the engine seems to run fine. When I plug it back in, the idle jumps back up to 3000 RPM. Is this the problem or is it a red herring?

What does the air valve do? How does it work? Is it supposed to be open at idle? Is it safe to run my car with it unplugged?

Still hunting for my Bently manual. dangit.

--
Greg P. 1988 240 DL 'Olga' 170,000 miles

The IAC valve opens and closes letting more or less air to bypass the closed throttle plate. It sounds like it is stuck open you should remove it and try to clean it out it may be gunked up and not moving. Dan
--
85 245 M46 195K, 92 245 A70 123K

I'll try that tomorrow.

Found my Bently book finally. Yeah now I see how that is supposed to work.

It might be the valve I suppose. Seems like it is going wide open when I plug it in, but car runs fine with the connector off.
--
Greg P. 1988 240 DL 'Olga' 170,000 miles