Mechanics

HIGH IDLE, 'HUNTING IDLE'

1993 Mercedes Benz 500sl

Engine Performance problem
1993 Mercedes Benz 500sl V8 Two Wheel Drive Automatic 107, 00 miles

I get different answers from different people, about the same symptom.

Turn on the car, idle at 1,100 rpm. Then the idle is 'hunting' ( up/down). Driving the car, it is fine & smooth. A new throttle actuator, new engine wire harness, new tune-up. Car is never in " limp mode".

Has anyone actually experienced this problem, and found a fix?

I promise. I am willing to donate. But so far I have been going round / round.

( Consider this a " test question"?
Avatar
Mountie55
September 24, 2009.



Sounds like you may have a vacuum leak. With engine idling carefully spray around intake area with carb cleaner. If the engine rpm changes you have found a leak.

Tiny
Jack42
Sep 28, 2009.
Just another thought, I glanced at a fix database. Suggestions, main wiring harness-- throttle actuator-- throttle cable, if all that checks out, check for a faulty air mass sensor. Pay attention to Jack, he always helps me, when I get in trouble.

JDL
Sep 28, 2009.
I'll try the 'ol trick with carb cleaner. ( But other than the high idle & 'hunting' idle, the engine is smooth & strong)

New engine wire harness, just put in a rebuilt Throttle Actuator, swapped an E Gas module & didn't improve. ( New tune-up).

Tiny
Mountie55
Sep 28, 2009.
All checked out. My '93 500 SL doesn't have an, air mass sensor.

(Which I am talking to you guys).

What do you know about that Accellerator Peddle/ Position sensor ( mounted on gas peddle bracket?)

Tiny
Mountie55
Sep 28, 2009.
My bad, maybe I was looking at the wrong engine family?


http://www.2carpros.com/forum/automotive_pictures/170934_benz_air_flow_sensor_1.jpg



If you get the feeling I don't know what I'm doing, some days I get the same feeling. Thanks alot Mike.

JDL
Sep 28, 2009.
( I miss-wrote my silly comment).

" Which is WHY I am talking to you guys". Trying to nail down cause, because I am getting different suggestions.

Thanks for that drawing ( small to read). But where is it located?

Tiny
Mountie55
Sep 28, 2009.


http://www.2carpros.com/forum/automotive_pictures/170934_mercedes_maf_sensor_1_1.jpg




http://www.2carpros.com/forum/automotive_pictures/170934_mercedes_air_flow_sensor_2_1.jpg



Sorry for the picture quality, I tried to magnify a little, If I magnify too much, you can't tell anything about the picture. B2/3 and B2/4 is the location.

When I said," thanks alot Mike", Mike is my boss, he told me to take a look at your post. I guess I waited too long, Jack was already talking to you. I'll help anyway I can.

JDL
Sep 28, 2009.
Thanks, much appreciated.

When I remove my large air box, you see a single 3" opening about in the center of the intake manifold, with the Throttle Actuator under it. The airfilter/airbox has a 3" opening in the center/bottom.

I see no air sensors as shown. I have air inlets on either side of airbox, into the airfilters, but no sensors.

Hey, I notice your address is in Anaheim? I'm in Corona Del Mar.? Possible to just drive the beastie to you? ( $) Donation?

Tiny
Mountie55
Sep 28, 2009.


http://www.2carpros.com/forum/automotive_pictures/170934_mercedes_air_mass_meter_1.jpg



The picture came from a Mercedes parts book for your year make and model. I can't tell you what to replace, only make suggestions on what to check. Sometimes the databases and partsbooks are not correct, but, that is all I have to go on.
Because this is an internet site, the people that help out here are from all over the world. I live in Oklahoma.

JDL
Sep 29, 2009.
I like that state. ( I used to haul a prototype Sooner Trailer for Team Mears / INDY. NICE trailer!

Uh, I always learn from you guys. Maybe my Mass Sensor is the single opening on top of my Throttle Actuator. I'll take a look.

( I am working on getting a repair manual. That'll help!)

Tiny
Mountie55
Sep 29, 2009.