Help: The Erratic Idling While Coasting... Your Thoughts? - PeachParts Mercedes-Benz Forum

tnarg · #1 11-22-2005, 12:00 AM

I have a problem. My 1983 300D Turbo tends to hunt/ idle erratically while coasting downhill or coasting to a stop from about 35 mph, about. The idle smoothes out as the car comes to a stop. The tachometer reads in vicinity of 1000 RPM's when "hunting" occurs. I know that "hunting" can occur if the timing is not right but the engine starts right up and sounds pretty good at idle and while on highway. Is this timing chain stretched? Your suggestions are greatly appreciated.

ps. i've replaced the timing chain tensioner already.

dkveuro · #2 11-22-2005, 12:05 AM

Slightly reduced coupling drag.....or......throttle rods/linkage hanging up on engine as it opposite torques......Need to check linkage free play, reduce idle speed and adjust idle stabiliser bolt on back of pump.

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tnarg · #3 11-22-2005, 12:29 AM

Quote:

Originally Posted by dkveuro

Slightly reduced coupling drag.....or......throttle rods/linkage hanging up on engine as it opposite torques......Need to check linkage free play, reduce idle speed and adjust idle stabiliser bolt on back of pump.

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Thanks for the response.

what do you mean by "reduced coupling drag"? please explain.

by the way, the linkages work freely and all lengths are per factory, idle is set at 700 rpm in park with engine at op. temp.
I thought the idle dampener bolt on the IP is for regular idling in park or when car is not moving? Am I wrong? Any other suggestions?

dkveuro · #4 11-22-2005, 12:41 AM

Damaper bolt/lock nut adjustment controls rack idle position against the governor.
You may need to adjust it slightly.

'Reduced coupling drag' is the engine not having to rotate the drive train like it does when coast idling or under way. If you where able to idle your engine disconnected from the drive train, you would find it had a higher idle speed.

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tnarg · #5 11-22-2005, 07:43 PM

Thanks for the input

Then what are the symptoms of a stretched timing chain?

My 300 has more miles on the odometer because it started to work intermittantly when I bought it; then it stopped. I had it repaired over a year ago... it may have another 30k on it that's not accounted for. The previous owner didn't take as good care of it so I expect some additional wear.

dkveuro · #6 11-22-2005, 10:46 PM

Quote:

Originally Posted by tnarg

Thanks for the input

Then what are the symptoms of a stretched timing chain?.........................................

Hunting when coasting ?

Most likey not......it's a measurement thing....Needs checked when you do valve gaps. The 5 cylinder chains are not overly problematic....usually see 2 to 5 degrees retard at the cam when around 200,000 ml plus.

I take it you still have not found the problem ?

There is a s-l-i-g-h-t possibility the rack is not returning to low fuel position, or seeing a little turbo positive boost pressure.

Check the boost lines and the connectors for clear from the manifold banjo bolt to the pump banjo bolt..

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