What in the world is wrong with my '94 C280? - PeachParts Mercedes-Benz Forum

brookspw · #1 08-07-2009, 02:31 PM

I have two issues right now (well, my car does, anyway):

1. Idle surging
2. Rough ride / feels like front wheels out of balance.

Problem 1 / Idle Surging -- Had head gasket replaced in March. R/R cracked the wiring completely on the old EA/actuator. Replaced it with one from a salvage car, a 96. Code gave us the air flow meter -- got an aftermarket one. Seemed like all was well. Then, it started surging at idle. 600 to 1,100, but would run fine when driving. Lately, surge got worse, engine is rougher driving, and I get real rich type exhaust at idle and MPG is down 5 mpg. Reading OK,,, I give up gave me the idea to spray soapy water at intake gasket, hoses, etc. I found no leak. I also tried to check the purge valve. Felt no pulsing. Tried to "jiggle" it and somewhat dislodged it and snapped it back.
-- NOW IT RUNS GREAT. Well, sometimes I get a "tiny" bit of idle fluctuation but otherwise it is smooth as silk.
-- Coincidence? -- Soapy water temporarily plug a pinhole leak? -- Did "jiggling" the purge valve help?

Problem 2-- In March, had tie rods, ball joints, steering damper, etc. replaced and got fresh alignment, rotate and balance on good tires.
-- New brakes, new rotors.
-- A month ago the road noise began to build. Replaced wheel bearings thinking that was it. Nope. Mechanic said it was the tires that needed an alignment and were wearing unevenly.
-- Yesterday, I got get an alignment. I am 100% in spec -- completely aligned although the front tires did show odd wear. Rotated front to back and rebalanced on Hunter 9700.
-- Shocks seem to be working just fine. They were replaced 30k ago and car immediately settles on the rebound, no bouncing at all.
-- Road noise is a little better but not gone.
-- Out of balance shimmy is still there, especially 75-80 mph.

What is your take on either situation?

Ferdman · #2 08-08-2009, 05:31 AM

A slipped belt in one or more tires could cause the shimmy at 75-80 mph. If possible, swap a good set of wheels/tires for yours and see if that resolves the problem.

brookspw · #3 08-08-2009, 09:24 AM

Quote:

Originally Posted by Ferdman

A slipped belt in one or more tires could cause the shimmy at 75-80 mph. If possible, swap a good set of wheels/tires for yours and see if that resolves the problem.

The shimmy is definitely in the front. I rotated the tires so it should have eliminated a slipped belt. They were also balanced on a hunter 9700 which would have detected a slipped belt, is my understanding.

brookspw · #4 08-08-2009, 07:44 PM

Update on my surging idle issue.

It runs smoothly now...some of the time. It seems to be smoother when cold than hot, but is intermittent in both.

Thanks to Arthur Dalton's help I have eliminated the purge/regen valve as the culprit. It is definitely clicking now to open/close the valve. Frankly...I never heard it before, but I do now. Maybe it was stuck closed or not closing all the way and it was yet another problem. But...I still have the idle surge part of the time.

His next suggestion was to see if I have an internal leak in the fuel pressure regulator diaphragm, which I'll check tomorrow.

I removed the air flow meter, checked that intake flex tube it is attached to, rubbed wd40 on the seals and internal ends of the tube just to make sure no external air is getting in. This is a new air flow meter, by the way.

I get horrible gas mileage from it running rich when surging...maybe I have excess fuel leaking from the regulator diaphragm...we'll see.

Arthur Dalton · #5 08-08-2009, 08:11 PM

Might also want to go into HFM Module and see what's detected/ stored there...

http://www.autolib.diakom.ru/CARS2/pribor/cs1000/manual/cs1000_mb.pdf

Page 31

brookspw · #6 08-14-2009, 09:54 AM

HFM is being checked on Monday.

Here are couple more symptoms that I wanted to share, just to see if it helped to diagnose.

Driving down the interstate, running fine, I'll get a "miss" almost like letting off the gas real fast. It picks right up instantly and runs fine.

I got 12 mpg on the last tank. 12.

This morning when I started it up it ran fine. I drove 15 miles. All fine. Then, sitting at a red light I'm thinking "man, this thing is idling smoothly" when right out of the blue, at idle, it started running rough and surging.

mbinnashville · #7 09-25-2009, 10:30 PM

Quote:

Originally Posted by brookspw

I have two issues right now (well, my car does, anyway):

Problem 2-- In March, had tie rods, ball joints, steering damper, etc. replaced and got fresh alignment, rotate and balance on good tires.
-- New brakes, new rotors.
-- A month ago the road noise began to build. Replaced wheel bearings thinking that was it. Nope. Mechanic said it was the tires that needed an alignment and were wearing unevenly.
-- Yesterday, I got get an alignment. I am 100% in spec -- completely aligned although the front tires did show odd wear. Rotated front to back and rebalanced on Hunter 9700.
-- Shocks seem to be working just fine. They were replaced 30k ago and car immediately settles on the rebound, no bouncing at all.
-- Road noise is a little better but not gone.
-- Out of balance shimmy is still there, especially 75-80 mph.

What is your take on either situation?

I have a '95 C280 and I was having the EXACT same vibration/bad shimmy problem you are having, and uneven tread wear. Took it to my MB dealer who does my work, and it was the control arm bushings. They replaced them, and it drove like new again. Have those checked out.