More M103 rough idle problems.....WHY??? - PeachParts Mercedes-Benz Forum

lsmalley · #1 03-25-2015, 02:21 AM

This is becoming a constant nightmare. First it clears up for months and then it returns. On and off, same thing. Its not even a continuous problem as it will completely go away on certain days. The car will idle rough, and have a slight stumble/hesitation on acceleration from standing. Here is the list of things that have all been done:
Spark plugs replaced today
Valve stem seals replaced last week
Oil/oil filter changed last week
Coolant flushed/changed last week
Was getting Error code 12 for EZL, replaced this week. code is now gone.
O2 sensor replaced 8/2014
Radiator replaced 7/2014
All radiator/coolant hoses replaced this year
Voltage regulator replaced 7/2014
Fuel filter replaced 8/2014
Fuel pumps replaced 7/2014
Distributor cap replaced 3/2014
Ignition rotor replace 2014
Spark plug wires replaced 1/2014
Throttle body gasket replaced last week.
Both IACV hoses replaced 3/2014
IACV tested ok 2015
O2 sensor tested ok 2015
Vacuum hoses replaced 2014
Alternator upgrade to 120 amp 6/2013.

Not receiving any check engine codes other than code 11 for secondary air injection (disconnected smog pump). I checked the duty cycle and the readings fluctuate rapidly between 45% - 55% per the ke-jetronic write up. There was a nice puddle of oil in the intake manifold after I removed the throttle body. Once the valve stem seals were replaced, all is dry now. Anyone got any suggestions?

lsmalley · #2 03-26-2015, 04:27 AM

I pretty much replaced everything fuel, air, and spark related....but I noticed I did not check the injectors. After checking the injectors, several were spraying streams and non uniform patterns, I had some spare ones so I swapped them out as well as my cold start valve. While I had the fuel distributor off I also replaced the rubber boot at the bottom and also changed out the throttle position sensor. While I had everything off I removed the plugs and I used 2 cans of carb cleaner through the injector ports and cycled the engine after each series to clean everything. I noticed some residual oil washing out into the intake manifold so I continued until only clear carb cleaner came out. I buttoned everything back up and went on a test drive and no stumbling or hesitation. Idle was super smooth. I'm almost positive that the injectors were the problem, but since I replaced/changed so much it's hard to tell and I will not try to find out either

pawoSD · #3 03-26-2015, 02:02 PM

It seems with the CIS cars that eventually pretty much all of it has to be replaced for them to run properly. Went through the same ordeal with my 300E when I had it...

The v8's seem less prone to the problems of the smaller engines it seems, at least in my experience.

MBeige · #4 03-28-2015, 08:49 PM

What's the compression on the cylinders? Is EHA original?

lsmalley · #5 03-29-2015, 05:23 AM

Problem was solved.

Duke2.6 · #6 03-29-2015, 11:35 AM

So what was the problem and how did you solve it?

Duke

lsmalley · #7 03-29-2015, 12:08 PM

Quote:

Originally Posted by lsmalley

I pretty much replaced everything fuel, air, and spark related....but I noticed I did not check the injectors. After checking the injectors, several were spraying streams and non uniform patterns, I had some spare ones so I swapped them out as well as my cold start valve. While I had the fuel distributor off I also replaced the rubber boot at the bottom and also changed out the throttle position sensor. While I had everything off I removed the plugs and I used 2 cans of carb cleaner through the injector ports and cycled the engine after each series to clean everything. I noticed some residual oil washing out into the intake manifold so I continued until only clear carb cleaner came out. I buttoned everything back up and went on a test drive and no stumbling or hesitation. Idle was super smooth. I'm almost positive that the injectors were the problem, but since I replaced/changed so much it's hard to tell and I will not try to find out either

Posted above.

pawoSD · #8 03-30-2015, 12:23 AM

When I had my 300E I too replaced all the injectors and it improved engine operation significantly....for about 10k miles....then it was back to being troublesome...I think mine needed a new wiring harness but I opted to get rid of it as the rest of the car was not in very good shape anyways.