Trouble when idle and when taking off - Page 2 - PeachParts Mercedes-Benz Forum

sbourg · #16 11-25-2003, 01:33 PM

The fuel distributor COULD be the problem. When meting out small quantities of fuel at idle, irregularities would tend to show up more than at a high rate of delivery. At idle, the metering slits keep the secondary pressure low enough that rates could vary significantly from injector to injector.

However, there are a lot of other possible causes of your symptoms. We can't know for sure what your tech has done to eliminate other possibilities, but some tests are pretty simple. For instance, to rule out a worn pot in the airflow meter, disconnect the EHA. If idle smoothes out, then the fuel distributor is NOT the issue. Likely the airflow meter pot has a worn spot.

Steve

mhingram · #17 11-25-2003, 03:52 PM

mattsuzie,
I have had a very similar problem please see thread:
help please
I asked originally if it was the coil got off the topic and rebuilt my entire fuel system no luck, finally replaced the coil. Thats what fixed it. Steveb helpled me alot with the fuel system, I would doubt it is your fuel dist but, I would follow the basic principal and make sure your lambda is working right. BUT first get you ignition checked on a scope, although mine looked okay on the scope it was not perfect and I should have gone with my gut. There are a couple of good people in RTP Joep is on this board. I used to work ar a shop called the Foreign Service owned Dave Pettengill http://www.theforeignservice.com
hope this helps, All I can say spend the time with diagnostics you can throw alot of money at this in parts. I spent a lot of time on it but not too much cash on parts mainly replacing the rubber. The coil was the most expensive part.
good luck
m

MARIO FARIAS · #18 11-25-2003, 11:52 PM

pLEASE try the EHA sensor. Messure the voltage at pin 2, it has to be 800 Milivolts +/- 250 milivots. If not, rotate little bit, few degrees till get 800 milivots aproximatly.

It could be burned or broken pins.

See a lot of EHA threaded.

Mario Farias
laprefar@cantv.net

#19 12-01-2003, 11:58 AM

Still no luck. I do not know some of the finite details of what the tech checked. I hate to take it to the dealer though, for the may cost me an arm and a leg , but I guess I have not choice.

Any more ideas?

joe p · #20 12-01-2003, 12:20 PM

Ok, so your in RTP and I'm right off 70, one block shy of Duraleigh Rd. Why not drop in and show me exactly what your problem is. Normal fuel head complaints are leakage, skips or bad stumbles. Most bad idles are vacuum leaks, bad/dirty injectors or CO adjustments. However, coils, EZLs and sticking egr valves will also cause 'em. On rare occassions you'll find a M117 with a guide walking in a head causing a intermitent skip and piss poor idle when not skipping. (these are also hard as hell to get a firm diagnosis on)

What I'd like to know is what the base duty cycle readings are and O2 response times. Drop in, we dont bite.

Joe

engatwork · #21 12-01-2003, 09:02 PM

Quote:

bad/dirty injectors or CO adjustments.

I just had a 300SE experience a poor idle situation and these were the culprits. The mixture was way too lean and indicating around 68% duty cycle. After setting it at around 45% it smoothed right. The tech also did a "carbon clean" which I think is running some BG44K through there. It seems to me that the Bosch CIS FI is a pretty good FI system.

joe p · #22 12-02-2003, 07:46 AM

Yeah, its ok. Gotta remember, thats late 60's technology so its a bit rude. CIS-e and its variants are really very simple, reliable systems that give people fits. The main reason is the system works backwards from conventional thinking, higher pressure = leaner mix, lower pressure = richer mix. Drives people mad.

Joe

#23 12-02-2003, 12:20 PM

I am running the 44k stuff in it now. The tech also leaned out mixture some. I will see if I can take it to Joe for a look.

sjcruiser · #24 12-02-2003, 01:26 PM

Mattsuzie,

Mine had the very same symtoms. It started out with slight shakes/vibrations at idle. As soon as I tapped on the gas, it's glass smooth again. For two years, I've tried (new OEM parts): engine mounts, transmission mount, plugs, cap & rotors, injectors (did try Redline, Chevron cleaners first); and the problem persisted, but worsening over the period. Took it to an independent shop a second time, found that it's indeed the fuel distributor (had previously thought it's the injectors - thus the replacements but they are originals (185K) anyway.)

Bought the re-man. distributor from germanstar.net (less than $500 bucks). Driving it home, all I could say is WOW...

You could check it by loosening each fuel line on the distributor (mine turned out to be no fuel output at all on cyl.#3 at idle - I learned it the hard way).

Hope this helps,
Frank.

joe p · #25 12-02-2003, 02:27 PM

Just saw the car. Dead miss off idle, intermitent skip at idle. (like a lean misfire) Popped a plug out, lots of oil for a 2 week old plug. Personally I'm tinking guides but, there are still several other posibilitys. It also has some lifter type noise and more than a few miles on it. I recomended he replace the plugs and see if it clears out for a few days and go from there. Nice guy BTW.

It just dosen't strike me as a fuel head problem, more like a bad resistor tip or fouled plug. However, the 5.6's I've had with walking giudes have done a remarkable job of mimicing a fouled plug or bad wire.

Joe

standard125r · #26 12-02-2003, 07:03 PM

FYI. This is common on these cars. My 560 SEL AMG has had this problem since I got it. I cleaned the ICV, replaced check valves in the pump, then went to the stealership. I have a good repor w/the the head tech who said that Mercedes recommend running one bottle (the big one)of Techron through the system, if there is no change do a second bottle. DO NOT put in three! If you do you will have to replace not only the injectors, but also the fuel head. If this doesn't work then the fuel distributer is gummed up, and will have to be replaced as no mere mortal can rebuild them. I got a used one from Silver Star for $400, off a car that came in wrecked, but running. Fixed the problem in about 20 minutes.

tonyhito · #27 12-02-2003, 11:35 PM

I have the same problem too with my E320. Please read my thread: "New Member Needs Help". Mine started after I cleaned the egr crossover pipe. I think it is vaccum related but can not find a leak. Vaccum leak could affect air/fuel mixture and should affect the idle. But how do you go about checking for vaccum leaks? My model does not have a Throttle valve switch, or whatever they are called.

#28 12-04-2003, 08:50 AM

Interesting that the car starts out completely OK or almost OK for the first 3 miles or so after sitting overnight. Then when the engine is warmed up after about 5 miles the bumbling and stumbling starts. If it was the fuel distributor, does it make sense that after the car sits over night that it improves itself for the first 3 miles the following day?

I only had time to look at 4 of the plugs on one side of the block. The gap was .022" through .032" (pretty tight) - It does not appear that the Tech put the right gap on it. I widened the gap to about .037" on the four. I hope to look at the other 4 over the weekend. After the 44K fuel additive, really not that much change that I can tell.

#29 01-01-2004, 06:48 PM

Had the wires replaced with Mercedes wires and put in new plug and the problem still exists. This tech says that it is not the fuel distributor.

Odd that from 0-10 mph it is crummy, after that it is fine.

mhingram · #30 01-01-2004, 07:00 PM

A new coil fixed my stumble on acceleration. m