Worked on 300E, now it stalls with idle valve connected! - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #1 12-04-2008, 03:00 PM

If your idle control valve is anything like the one on my BMW this might work. Remove the valve and spray into it with carb cleaner. mine was stuck in a partially opened position due to gunk. I had to spray it about three times before it loosened up.

Also try putting it back on and then disconnecting the O2 sensor. If the engine runs better, the sensor is shot.

pawoSD · #2 12-04-2008, 03:05 PM

I tested the idle valve when I had it off, and it operated properly when I applied 12V to it.....doesn't seem to be stuck, I cleaned it out a few times with carb/throttle cleaner too....

Oracle12345 · #3 12-05-2008, 06:29 PM

Quote:

Originally Posted by LUVMBDiesels

If your idle control valve is anything like the one on my BMW this might work. Remove the valve and spray into it with carb cleaner. mine was stuck in a partially opened position due to gunk. I had to spray it about three times before it loosened up.

Also try putting it back on and then disconnecting the O2 sensor. If the engine runs better, the sensor is shot.

the fuel injection and idle the 300E is controlled by the PCM not by a control valve and I can prove that.

To check fuel pressure you need a fuel pressure tester

http://www.sears.com/shc/s/p_10153_12605_00902169000P

Whatever you disconnected to make the problem go away was not the idle control valve since the system doesnt have one. The round part with 2 prongs is the idle speed adjuster.

Also check this:

test coolant temperature sensor
test starting device of KE fuel injection system

I need your email for those docs btw

tinypanzer · #4 12-05-2008, 06:39 PM

My 300SE had the same exact symptoms after my coolant temp sensor broke. Seriously, the same EXACT symptoms except I never tried disconnecting the idle circuit.

But I would have to hold the gas when starting, make it rev to 2K for a couple minutes, then it ran fine.

Worth a check, very easy to test. I just posted how to test this in another thread.

-tp

pawoSD · #5 12-11-2008, 11:44 PM

Coolant temp sensor has been replaced. No change. Trying to start with the valve plugged in results in it struggling to start, but does if you push the throttle a bit, but it won't idle. Letting off throttle results in the engine shutting down. Disconnect valve, starts and idles fine....with a sliiiiiight miss every now and then.

New development. Temp sensor does do something, connecting and disconnecting it while car is running makes the switchover valve trigger/not trigger.....doesn't affect how the engine runs, but it does do something.

I wondered about the intake air temp sensor.....so while it was idling cold (and missing a bit) I unplugged that too, voila....idle went up by 100-150 or so (to about 650) and smoothed out, no missing at all. Smooth as silk.

Whats the deal here?! This engine seems to like less and less electronics to be active! As a result of these two things unplugged the car runs smoooth and nice when driving, idles great, starts great....everything great. Very annoying. Check engine light on. Diagnostic light gave code 18 (idle valve illogical signal) and now code 13 too (intake air temp value illogical)

Makes sense sure, but with them plugged in it runs poorly or not at all.

Plugging in the idle valve while the car is running does not affect it....this may be because it has already disabled the connection due to no signal though....so it may be ignoring it.

Plugging in and unplugging the air intake temp sensor results in lowering idle and a bit of missing (when plugged in), to smooth and slightly higher idle when its unplugged.

Help?! I'm probably going to just leave it as is......I'm doing a coolant flush and thermostat replacement this weekend and possibly a trans fluid replacement, but other than that I may just leave that stuff unplugged and leave it be for a while. Perhaps later on I'll have the dealer diagnose it.

pifcat2 · #6 12-12-2008, 12:12 AM

Did you read Lyle's docs, they explain much of each components functions?

pawoSD · #7 12-12-2008, 12:41 PM

Quote:

Originally Posted by pifcat2

Did you read Lyle's docs, they explain much of each components functions?

No.....where might I find these?

I have the W124 bible, and understand how the system works....but that still doesn't explain why when everything is plugged in it doesn't start/idle correctly. (With no computer codes by the way)

Initially it would start with about 10 seconds of cranking with everything plugged in, then I did some work and replaced some tubing and such, and then it would not start unless I unplugged the idle control valve. It runs so nicely with that and the intake air temp sensor disconnected that I may just leave it that way, and have the dealer diagnose it sometime in the future when I have more $$ to throw at it.

pifcat2 · #8 12-12-2008, 01:37 PM

Quote:

Originally Posted by pawoSD

No.....where might I find these?

I have the W124 bible, and understand how the system works....but that still doesn't explain why when everything is plugged in it doesn't start/idle correctly. (With no computer codes by the way)

Initially it would start with about 10 seconds of cranking with everything plugged in, then I did some work and replaced some tubing and such, and then it would not start unless I unplugged the idle control valve. It runs so nicely with that and the intake air temp sensor disconnected that I may just leave it that way, and have the dealer diagnose it sometime in the future when I have more $$ to throw at it.

He offered to email them since they are large documents.

If you are happy the way it runs, you're done. If you want it to run how it was designed then you have more work. I didn't like that the prior mechanic unplugged my ICV and added a helper spring...

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