M103 Misfiring/fouled plugs issue.... - Page 2 - PeachParts Mercedes-Benz Forum

Bigdaddybenz · #16 01-10-2009, 05:50 AM

Definitely VALVE SEALS!!!! Been there, done that!

George560sel · #17 01-10-2009, 06:30 AM

This is from my service manual.
Model 124, test data for engine at normal operating temp

minimum compression pressure at (normal compression) approx 12 bar, (low compression) approx 7.5 bar.

Allowable difference between cylinders max 1.5 bar

ignition cable w/ spark plug connector 700-1300 ohm.

babymog · #18 01-10-2009, 02:09 PM

The compression test is a 1hour job on a 103. Once the plugs are all out, a remote-start switch in one hand, a rubber-ended compression gauge in the other, hold the rubber tip in each spark plug hole as you crank, quick and easy compared to the diesel version. Some things are actually easier with the gassers!

If you haven't already been following the thread, this: My 300TE Head Gasket Thread (yes pics!) one has a couple of nice photos of the M103 valve and rocker assembly.

pawoSD · #19 01-10-2009, 03:12 PM

Problem with doing the valve seals myself is that I have none of the following:

All special tools
Shop air supply (or any air supply)
confidence in doing it.

Anyways, today I re-gapped the plugs properly (my guess job was a bit off on most of them) None were really much dirtier than last time, so thats good...

Replaced distributor rotor and cap/cover, rotor was singed and scary looking, the cap was coroded and burnt, and the carbon tip was worn....only 2 of the tips measured properly on the ohm-meter!

I haven't started it yet, but I will be going out and doing so in a few minutes....I'll report back any improvement.

pawoSD · #20 01-10-2009, 05:48 PM

Well, it still ran with a miss/crappy. So out of frustration I slapped in the old champion resistor plugs that came in the car when I got it. Well what do you know, fires right up and runs smooth/powerful. No miss at all.

Explain that!!!

I just bought some el-cheapo "copper core classic" splitfire brand plugs....I am going to see how it runs on those......they were $1.29 each, I'm going to go gap them to .034" and throw them in and see how it runs.

Why does it seem to run better on the resistor plugs? Makes no sense.

dang50 · #21 01-10-2009, 06:23 PM

I'm afraid if you check www.splitfire.com Copper Core classic plugs are resistor plugs. Everybody says non resistor is the way to go. The dealership can provide them for less than platinums and you'll have the recommended plug in there. Also the exact proper heat range may be coming into play with other than recommended H9DCO.
I worked at a car parts store in the '80's when platinums came out and in Bosch plugs one platinum plug would replace up to 4 different heat ranges in the copper core. We had plenty of people bring platinums back because they wouldn't run right with the application being used.
Dan

mak · #22 01-10-2009, 10:54 PM

Do you know by chance what the ohm reading should be on the wires for a M103?

the ignition wires are normally solid . the problem is at the plug connectors over a period of time the rubbber inside becomes conductive due to oil/water residues .The ignition will then develops a light miss and hesitation on acceleration.
when you remove the plugs look for a corona ring on the porcelin portion of the plug indicating a leaking plug connector. resistor type plugs compound the problem. use non resistor bosch HD 9c plugs

mak
300se 103

pawoSD · #23 01-10-2009, 10:59 PM

Quote:

Originally Posted by dang50

I'm afraid if you check www.splitfire.com Copper Core classic plugs are resistor plugs. Everybody says non resistor is the way to go. The dealership can provide them for less than platinums and you'll have the recommended plug in there. Also the exact proper heat range may be coming into play with other than recommended H9DCO.
I worked at a car parts store in the '80's when platinums came out and in Bosch plugs one platinum plug would replace up to 4 different heat ranges in the copper core. We had plenty of people bring platinums back because they wouldn't run right with the application being used.
Dan

Well, it runs excellent on them, so I'm leavin' them in for now. The non resistor bosch plugs got all sooty and gross after barely 1500 miles and wouldn't run right even after I cleaned them off. (Sputtering and missing). Threw in these $1.30 apiece china plugs, and she's running awesome, and tons of power/rev's freely and smoothly. I'm a believer. So until it stops running smoothly, I'll be keeping them in it.

Oh, and it got 11mpg on the Bosch plugs on the last fillup. The mpg's continuously fell each fillup when using those plugs. Makes no sense.

The exhaust even smells normal/not oily or gassy with the splitfire plugs.

And I don't think it needs valve seals yet, it doesn't put out the slightest bit of blue exhaust, even if you rev it up in 2nd, coast, then hit the gas again....nothing. Oil consumption is less than a qt per 1000 miles.

Hit Man X · #24 01-11-2009, 01:57 PM

M103s don't tend to smoke much during oil consumption from what I have seen. Don't judge anything by simply that. Mine doesn't, 260k and the head hasn't been rebuilt.

Keep the oil weight around 0/40 or 5/40. Plenty of film at high RPM and quick pressure on cold starts.

Have you pulled the old cap/rotor yet? They don't last that long as the M103 is a high rev car... just like the rest of the accys. With a poor arcing setup...

Do you have a lazy injector or many?

Do the stem seals to rule them out, under $20 and a few hours. Plus you get a new valve cover gasket and oil cap seal then to help idle vacuum. Also the upper timing cover always leaks, go ahead and replace the seals while it's apart, then toss on new cap/rotor.

Your PO sounds like a moron, so you get to basically replace everything and start fresh to get a solid base.

pawoSD · #25 01-11-2009, 02:04 PM

Quote:

Originally Posted by Hit Man X

M103s don't tend to smoke much during oil consumption from what I have seen. Don't judge anything by simply that. Mine doesn't, 260k and the head hasn't been rebuilt.

Keep the oil weight around 0/40 or 5/40. Plenty of film at high RPM and quick pressure on cold starts.

Have you pulled the old cap/rotor yet? They don't last that long as the M103 is a high rev car... just like the rest of the accys. With a poor arcing setup...

Do you have a lazy injector or many?

Do the stem seals to rule them out, under $20 and a few hours. Plus you get a new valve cover gasket and oil cap seal then to help idle vacuum. Also the upper timing cover always leaks, go ahead and replace the seals while it's apart, then toss on new cap/rotor.

Your PO sounds like a moron, so you get to basically replace everything and start fresh to get a solid base.

I'm going to wait till we build up some more $$ before I get the valve seals done....I'll get a quote tomorrow from the stealer on it. (I don't have the resources to do it myself)

It has a new: coil, rotor, cap, cap cover, and spark plugs. I've also changed the rubber tubing for the idle control valve, the valve itself, and the temperature sensors. This car has cost a fortune!

We'll see on the valve seals...if its not too expensive I'll just get it done right away so I don't keep fouling plugs....that'd be nice to not be pulling them on a bi-weekly basis!

As for oil, its currently on Mobil 1 0w40....think the turbodiesel truck 5w40 would work as well or better? Just curious....

Hit Man X · #26 01-11-2009, 02:09 PM

Quote:

Originally Posted by pawoSD

I'm going to wait till we build up some more $$ before I get the valve seals done....I'll get a quote tomorrow from the stealer on it. (I don't have the resources to do it myself)

It has a new: coil, rotor, cap, cap cover, and spark plugs. I've also changed the rubber tubing for the idle control valve, the valve itself, and the temperature sensors. This car has cost a fortune!

We'll see on the valve seals...if its not too expensive I'll just get it done right away so I don't keep fouling plugs....that'd be nice to not be pulling them on a bi-weekly basis!

You just need to rent a valve spring compressor and you can rotate the motor to TDC on each piston when you do them and put some string or something in there to support the valves.

OR justify this as a reason for a compressor.

When I bought my 300SEL, I just replaced everything due to mileage. I had a decent amount of records and dealer stamps in the booklet (until about 190k) but from there was hit/miss until 221k. So about 30k of nothing.

1/4 of a million miles was enough, so I just resealed/cleaned/replaced anything related to the motor.

Is your O2 sensor cycling properly? Lambda set properly?

pawoSD · #27 01-11-2009, 02:21 PM

Quote:

Originally Posted by Hit Man X

You just need to rent a valve spring compressor and you can rotate the motor to TDC on each piston when you do them and put some string or something in there to support the valves.

OR justify this as a reason for a compressor.

When I bought my 300SEL, I just replaced everything due to mileage. I had a decent amount of records and dealer stamps in the booklet (until about 190k) but from there was hit/miss until 221k. So about 30k of nothing.

1/4 of a million miles was enough, so I just resealed/cleaned/replaced anything related to the motor.

Is your O2 sensor cycling properly? Lambda set properly?

Mine is a California emissions setup car....(its from Nevada)....it has the diagnostic light and check engine light for the emissions system....if the O2 sensor was malfunctioning wouldn't that throw a code/light?

Depending what the dealer wants for the valve seals will decide if I get a compressor and do it myself....

Thats happened in the past...it might again.

The motor doesn't leak much, just a little bit by the timing cover. No idea on the Lambda....it gets about 20-21mpg....does that mean anything?

Hit Man X · #28 01-11-2009, 02:28 PM

Quote:

Originally Posted by pawoSD

Mine is a California emissions setup car....(its from Nevada)....it has the diagnostic light and check engine light for the emissions system....if the O2 sensor was malfunctioning wouldn't that throw a code/light?

Depending what the dealer wants for the valve seals will decide if I get a compressor and do it myself....

Thats happened in the past...it might again.

The motor doesn't leak much, just a little bit by the timing cover. No idea on the Lambda....it gets about 20-21mpg....does that mean anything?

I think the Check Engine light is only for the O2 closed loop. Not familiar with CA emission gassers

Don't forget oil leaks are also vacuum leaks...

G-Benz · #29 01-11-2009, 09:21 PM

When's the last time you changed your spark plug wires? Why do I ask?

My 300E performed like crap for months (after running great following a total top-end rebuild incl. head gasket). Plugs were fouled. Plugs replaced, and all was well for a few weeks. Pulled plugs again for re-inspection and they were once again fouled. Replaced plugs AND wires this time. Plugs stopped fouling, but I might add, that all of the excess carbon and fuel destroyed the O2 sensor, so I had to replace that as well.

pawoSD · #30 01-11-2009, 10:38 PM

Quote:

Originally Posted by G-Benz

When's the last time you changed your spark plug wires? Why do I ask?

My 300E performed like crap for months (after running great following a total top-end rebuild incl. head gasket). Plugs were fouled. Plugs replaced, and all was well for a few weeks. Pulled plugs again for re-inspection and they were once again fouled. Replaced plugs AND wires this time. Plugs stopped fouling, but I might add, that all of the excess carbon and fuel destroyed the O2 sensor, so I had to replace that as well.

Yeah they are not new.....I'll replace them at some point in the near future....they're $81 a set....so I was being cheap. This car isn't cheap.

I'm holding out to find a 300E in the junk yard with new wires on it.

Currently its running good, but if it fouls the plugs again quickly....wires/valve seals are on the list.