Worked on 300E, now it stalls with idle valve connected! - Page 2 - PeachParts Mercedes-Benz Forum

pawoSD · #16 12-04-2008, 10:20 PM

Ok get this, I went and started it tonight, outside temp is about 20F or so.....I cranked, and in under 2 seconds it fired off, with no throttle applied! It was running around 550rpm, but was missing a bit (shaking slightly from time to time) but evened out in maybe 30 seconds to a minute.....then ran fine. Idled at 650-700 or so, and I took it on a longer drive....ran great the whole way.....and the exhaust doesn't smell gassy like it did before.

Note: This is all now that I have Unplugged the Idle control valve!! This makes no sense! Warmed up and having been driven a while it idles around 750-800 in park/neutral with no loads on the engine. Idles around 600-650 with A/C comp or heavy electrical load (or both) And idles around 600-650 in drive or reverse. When driving it is responsive and feels perfectly normal and smooth.

How is this possible?!?

It still needs a coolant flush with MB coolant + a new thermostat.....and I might just replace the distributor cap/rotor/coil for the heck of it.

Oracle12345 · #17 12-04-2008, 10:47 PM

IF you would like to be educated on your cars fuel injection i can send you documents on it.

Jsut curious did you check your fuel pressure and for internal leaktightness?

pawoSD · #18 12-05-2008, 12:15 AM

Quote:

Originally Posted by Oracle12345

IF you would like to be educated on your cars fuel injection i can send you documents on it.

Jsut curious did you check your fuel pressure and for internal leaktightness?

That would be much appreciated. Which documents do you have? How would I check the fuel pressure? I have none of the required tools/equipment for that.....

Still doesn't explain why it starts and runs ok with the valve unplugged.....but stalls with it plugged in. Why?

Oracle12345 · #19 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 · #20 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 · #21 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 · #22 12-12-2008, 12:12 AM

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

pawoSD · #23 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.

babymog · #24 12-12-2008, 01:30 PM

The short version is that the CIS-E is basically the mechanical CIS (Constant Injection System), with electronics added to control emissions via a frequency-valve (can't remember what it is called here) on the side of the fuel distributor. With a fault in the system, such as un-plugging the O2 sensor, it will revert to the mechanical system where the air-flow sensor plate moves a metering pin and directly changes the injection flow rate (all six cylinders, all of the time, at the same rate).

You are indicating through your experimentation that the basic CIS including mechanical parts such as the fuel pressure regulator, and the fuel pump, the injectors and injection distributor, seem to be operating correctly, and likely (not certainly) within spec. When the electronic brain is put back into the loop (plugging in all components), it fails, which indicates that somewhere in a sensor, the computer, the wiring and grounds, there is something out-of-spec. There are restistance vs temperature values for the temperature sensors, and I believe values for the O2 sensor available and the sensors can be measured with a good DMM/VOM. They can also be bypassed using a resistance-substitution box and a few BOSCH connectors cut from junkyard cars to see if the proper resistance will create the proper running condition.

It is my further opinion, that the ignition system is in adequate condition based on your experimentation and previous postings.

Check the sensors, a couple of sensors out of spec can really make a car run poorly. I'm betting someone here knows the correct resistance for that intak-air sensor for example, you'll need the temperature at which you measured it BTW.

pifcat2 · #25 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...

Ferdman · #26 12-12-2008, 01:53 PM

pawoSD, I would resolve the idle control issue before tackling other maintenance items on your 300E; otherwise you're liable to complicate the situation further.

pawoSD · #27 12-12-2008, 02:02 PM

The only other maintenance I am doing is fluids/thermostat (runs too cool).....with the electronics taken out of the loop it runs fine, and you can't even get it to stall if you try. (even when cold, bumping the throttle, putting a big load on it (electrical, A/C, ect...) it still won't stall)

I'll keep checking sensors....I'm guessing the air intake one is bad...its not in very good shape physically....however the engine temp sensor is brand new. What other sensors should I check? Or, what others are there that could cause that problem? The air intake sensor is cheap, I'll pick one up sometime in the future and try that....perhaps the computer itself has issues....I'll figure it out eventually....

Oracle12345 · #28 12-12-2008, 02:21 PM

" I need your email for those docs btw"

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

Never got his email addy so I figured he didnt want them anymore.

But your stalling problem is the reaction of the pcm taking the inputs of all the sensors and devices and taking that information and making adjustments to the A/F mixture. its apparent that one of your sensors or part of your fuel injection is malfunctioning.

"thermostat (runs too cool)" is heading in heading in the right direction because if the thermostat is not working properly it will the pcm to run rich and stay in an open loop when the system should be in a closed loop.

Did you pull your plugs and see the color of them?

babymog · #29 12-12-2008, 04:04 PM

If you suspect the intake air temp sensor, and don't feel like continuing to order/pay/wait for each test, look up the resistance value for that sensor at (for example) 0C/32F, buy a reisistor at Radio Shack of that resistance value, plug it into the wire harness and see how it runs. I'm not a big supporter of buying parts until it runs correctly, that's what Betten does for me at ~$100/hour.

pawoSD · #30 12-12-2008, 04:04 PM

Quote:

Originally Posted by Oracle12345

" I need your email for those docs btw"

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

Never got his email addy so I figured he didnt want them anymore.

But your stalling problem is the reaction of the pcm taking the inputs of all the sensors and devices and taking that information and making adjustments to the A/F mixture. its apparent that one of your sensors or part of your fuel injection is malfunctioning.

"thermostat (runs too cool)" is heading in heading in the right direction because if the thermostat is not working properly it will the pcm to run rich and stay in an open loop when the system should be in a closed loop.

Did you pull your plugs and see the color of them?

I figured its a sensor issue, but I am not sure what all sensors it is looking at (how many are there that play a role?).....one is brand new, and the other is known bad...I'll replace it sometime in the near future. It runs sliiightly rich, but not real bad. Exhaust looks clean but has a slight rich smell to it....much better than it used to be though. Spark plugs have been replaced with the correct non-resistor Bosch. Old plugs were junky champion resistor style, they were a bit oily and dirty (as was expected)....but the engine does not burn/lose any oil. I've driven it nearly 1000 miles since its oil change (M1 0w40) and it has not lost any.

The thermostat could explain the slightly rich running, but not the cold start issue.....as its cold anyways. At running temp right now it hits about 67-69C or so.....tomorrow I'll fix that.