OM606 revving high - PeachParts Mercedes-Benz Forum

martureo · #1 05-28-2012, 11:32 PM

1995 E300 OM606. EGR blocked, otherwise no mods made.

Got into the car tonight to drive 45 miles home and the car idles at 1100rpm (doesn't normally do this). If my foot goes anywhere near the pedal it acts like I'm flooring it, even after you take your foot off.

Looked at linkage, nothing seems to be binding, linkage on top of valve cover returns to idle position when released and pedal travels full distance to kickdown switch and returns without hesitation.

I haven't been able to take off the intake to examine the linkage connection on the IP, but with a flashlight it looked like it was still connected.

Any ideas or help? The car is parked for the next few days, and not knowing enough about it I'll be taking it to well respected Indy shop at the end of the week.

anghrist · #2 05-29-2012, 12:05 AM

It could be as simple as failed temperature sensor, but I don't have enough familiarity with the non-turbo OM606 to say for sure.

Perhaps some of the others will chime in with some suggestions.

Diesel911 · #3 05-29-2012, 12:06 AM

If there is a Cable between the Throttle Linkages and the Pedal I would expect it is sticking.

benedict · #4 05-29-2012, 08:22 AM

Quote:

Originally Posted by martureo

1995 E300 OM606. EGR blocked, otherwise no mods made.

Got into the car tonight to drive 45 miles home and the car idles at 1100rpm (doesn't normally do this). If my foot goes anywhere near the pedal it acts like I'm flooring it, even after you take your foot off.

Looked at linkage, nothing seems to be binding, linkage on top of valve cover returns to idle position when released and pedal travels full distance to kickdown switch and returns without hesitation.

I haven't been able to take off the intake to examine the linkage connection on the IP, but with a flashlight it looked like it was still connected.

Any ideas or help? The car is parked for the next few days, and not knowing enough about it I'll be taking it to well respected Indy shop at the end of the week.

What is the condition of your wiring harness?

This car has idle control to compensate for A/C and I think alternator load. Some update idle control circuits will also increase revs when engine is hot to get the water pump speed up.

martureo · #5 05-29-2012, 08:26 AM

Quote:

Originally Posted by Diesel911

If there is a Cable between the Throttle Linkages and the Pedal I would expect it is sticking.

"Looked at linkage, nothing seems to be binding, linkage on top of valve cover returns to idle position when released and pedal travels full distance to kickdown switch and returns without hesitation."

There is no sticking.

martureo · #6 05-29-2012, 09:08 AM

Quote:

Originally Posted by benedict

What is the condition of your wiring harness?

This car has idle control to compensate for A/C and I think alternator load. Some update idle control circuits will also increase revs when engine is hot to get the water pump speed up.

No clue how to answer. I'm not very familiar with this engine or model. As far as I can see there is no mention in the service records of a new engine harness, and the records are quite complete.

Is there a way to inspect or test certain problematic areas?

Diesel911 · #7 05-29-2012, 09:40 AM

Pop the linkage off of the Throttle Lever so no Linkages are connected to the Fuel Injecion Pump. If the rpms do not drop you have at least eliminated any of the linkages as a source of the prblem.

If the rpms drop you have a problem with the Linkges from the IP back to the Pedal.

engatwork · #8 05-29-2012, 09:52 AM

You have to get to the throttle linkage down beside the injection pump and from the cruise control unit. You will want to clean and lube everything. It is best to do it with the intake manifold off. Pretty hard to get to with it in place.

I have had this issue on both of my 95 E300s.

martureo · #9 05-29-2012, 10:33 AM

Quote:

Originally Posted by engatwork

You have to get to the throttle linkage down beside the injection pump and from the cruise control unit. You will want to clean and lube everything. It is best to do it with the intake manifold off. Pretty hard to get to with it in place.

I have had this issue on both of my 95 E300s.

Thanks for the advice. The car is parked about 100 miles from me right now and I don't think I'll get anywhere near it for the next few days.

I'll report back after performing the above advised service.

connerm · #10 05-29-2012, 10:56 AM

I had the same problem with my 95. I cleaned and lubed them, but the problem came back when the weather turned cold. In Dec., when I had the intake off, I replaced both of those throttle linkage rods - problem solved. They were pretty cheap, like $25 for both.

Zulfiqar · #11 05-29-2012, 11:33 AM

If you can pull back on the linkage and the rpm drop then the linkage is stuck, if it still has high rpm you need to remove the ELR connector on the pump, if rpm drops to normal then check the wiring.

The idle control system is solely controlled by 2 things as input

1 - rpm sensor
2 - temp sensor

If the wiring is bad and shorting then you would have high rpm idle because the ELR negative can be seeing direct ground. I have chased this so much that I now know the wiring of this in and out. My elusive high idle problem was incorrect placement of a wiring pin in the ELR control socket.

ottomatic · #12 05-29-2012, 06:22 PM

http://www.peachparts.com/shopforum/diesel-discussion/308174-1995-e300d-glow-plug-issue-yes-ive-searched-2.html

read #25 & 26