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Discussion Starter #1
Okay, I've been reading the archives now for a week or so as I chase a recent high idle issue on my 560SEL. The quick background - did an engine swap, ran/idled fine. Took it in for emissions - failed. Pulled spark plugs - found one fouled with fuel. I took it back and swapped just that injector. Ran great when I dropped it back off - idle still fine. Got it back a few days later (passed emissions) and noticed idling higher - about 800-1000rpm when warmed up. Noticed on the bill that it said "cleaned throttle body", nothing else done to the car besides a/c service.

Today I tested the voltage at the air idle valve - a little more than 5 volts, so that seems to be a good reading. I then pulled off the air cleaner and noticed the air metering plate is just slightly down and I can hear a hissing noise like air is being sucked in. Is this normal and how it should be at idle? Or is that maybe the problem? I'm suspicious of that area due to no problems before and then the problem showing up and the note on the bill...

Thoughts?
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,084 Posts
I am not the expert, but from chasing down similar problems:
No fouled spark plugs now?
I have seen a mechanic check the throttle plate clearance for uniformity with a sheet of paper.
The plate can be bent easy by pushing down on the sides instead of the center.
Did you spray a water mist (slow down of idle), or carburetor cleaner (speed up) around the vac lines, injectors, and edges of the intake manifold to check for vac leaks?
Good luck
 

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Discussion Starter #3
Horst,

Thanks for this, I'll have a read over the weekend while I'm away. If it was closer I'd take the car along and tinker with it there, but 2 hours each way at today's gas prices makes for leaving the car at home (going camping in the motorhome).

To answer your questions, no, haven't checked for any of that stuff yet. I figured since it idled fine before it was emissions tested, and my vacuum gauge is all the way to the left, I'm doubting I have vacuum leaks/issues. I didn't pull plugs either to check for further fouling, but since 7 of the 8 were "clean" and I put a brand new injector in and it then passed emissions, again, I figured it was fine. But it can't hurt to check anyway like you suggested, just need the time to do it.

What's odd is occasionally it will idle lower or close to ok, making me also think it isn't fuel or vacuum issues, as you'd think they would either be there or not.

Also, more noticeable when warmed up then cold, ie the idle increases after motor reaches operating temps, closer to 750rpm when cold.

Thanks again.
Cheers
Markus
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
Joined
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40,084 Posts
The way I understand it, the idle valve controls the revs until the engine reaches operating temp. and the Fuel distributor / throttle takes over.
The 750 rpm when warm can be adjusted down ward.
Let me know if you need any more of the following files.
Cheers'
Horst
07 Mechanical/Electronic Injection - M116/4.2 L & M117/5.6 L

Test and adjustment work

* 07.3-001 - Additional Designations for Model and Components
* 07.3-002 - Models and Components Survey
* 07.3-004 - Vehicle Characteristics
* 07.3-005 - Influencing Parameters of Mechanical/Electronic Mixture Adaptation
* 07.3-009 - Influencing Parameters of Idle Speed Control
* 07.3-013 - Function Diagram CIS-E Injection System
* 07.3-105 - Testing on/off ratio
* 07.3-110 - Testing, adjusting engine
* 07.3-112 - Testing electronic idle speed control
* 07.3-120 - Testing fuel pressures and internal leakage
* 07.3-121 - Testing electrical components of CIS-E injection system
* 07.3-124 - Testing starting device
* 07.3-126 - Testing starting valve control
* 07.3-127 - Performing cold start
* 07.3-128 - Electrical wiring diagrams
* 07.3-130 - Checking fuel pump
* 07.3-135 - Checking injection valves
* 07.3-152 - Checking, renewing throttle valve switch
* 07.3-160 - Checking fuel quantity comparative measurement
* 07.3-165 - Checking fuel pump relay
* 07.3-167 - Checking kick down switch

Assembly jobs

* 07.3-205 - Removal, reinstallation of fuel distributor
* 07.3-207 - Renewing sealing ring for control piston
* 07.3-215 - Removal, reinstallation of injection valves
* 07.3-216 - Removal, reinstallation of insulating sleeve
* 07.3-220 - Renewing air flow sensor
* 07.3-225 - Removal, reinstallation of mixture control unit
* 07.3-230 - Removal, reinstallation of throttle assembly
* 07.3-245 - Renewing, centering sensor plate and checking and adjusting zero position of sensor plate
* 07.3-250 - Removal, reinstallation of CIS-E control unit
* 07.3-251 - Removal, reinstallation of idle speed control unit
* 07.3-255 - Renewing electro hydraulic adjusting element
* 07.3-258 - Renewing oxygen sensor
* 07.3-268 - Renewing rubber buffer for fuel pump assembly
* 07.3-269 - Removal, reinstallation of fuel pump assembly
* 07.3-270 - Removal, reinstallation of fuel accumulator
* 07.3-275 - Removal, reinstallation of fuel filter
* 07.3-280 - Removal, reinstallation of fuel pump
* 07.3-285 - Renewing check valve for fuel pump
 

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I then pulled off the air cleaner and noticed the air metering plate is just slightly down and I can hear a hissing noise like air is being sucked in. Is this normal and how it should be at idle? Or is that maybe the problem? I
Thoughts?
Normal. If it wasn't sucking in Some air it couldn't run.

Jonathan
 
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