Ok.... I own a 300e 1988 and last week it was running like crap. Like it was really hesitating and bogging out. So for starters I replaced the spark plugs with bosh plat. 4s and the wires. It ran fine. One week has passed and now it is back to the same thing. It feels like it is flooding it self out. Sometimes it even backfire in the carb. It is bogging out big time. When you push on the gas it barely goes and then it will catch (sometimes)and take off. Why did it run so smooth for a week. This is really weird. Did the plugs go bad that quick...and if so ...why? Please help if you can.

WasHappy

You likely found the problem by changing the plugs and wires, but platinum plugs don't always work well in older engines. I suggest that you install a set of regular copper plugs. call Phil at Fastlane if you need help identifying the correct spark plug.

Who is phil at fastlane? is that a web site? Why would those plugs last a year(last time I changed them) And this time only last a week? Im going to pull them anyway but I just dont get it. My reg. mechanic told me to use those plugs(bosh plat. 4s) last year...so I did. Could it be anything else? Its been raining here everyday. I was thinking maybe cap n rotor... Thank you for your reply post.

WasHappy

Fastlane is a source of parts; their banner is at the top of this page. Indeed, your problem could be other than the plugs. I hope someone with a better understanding of your model year will step in.
regards,
Mark

I was reading through the posts and thought to myself....o2 sensor.....alot of rain....pass. window doesnt work(right now)WET! I lifted up the floor and it was a small pond! Dried it up with a couple rolls of towels and used my wifes hair dryer on the o2 sensor.... looked at the connection and it was so corroded that one of the wires was broke. So I cleaned them and cut out the clips, soddered them together and put plastic shrink over them, then tape them and put them back in there dry little home. I unhooked the batt. prior and my engine light thats been on for about ooohhh (dont laugh) a year..... IS GONE!!! God I love this forum as I booked marked it and have figured out a bunch of other new things I can do.

WasHappy....... Is now happy again!

According to Fastlane either Bosch H 9 DCO or H 9 DC are right for your car ask Phil if your unsure. Old MB engine's don't like platinum plugs they were not designed to use them. I bet your car would run better with copper plugs.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Run it at 90 in 3rd to clean the plugs.

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Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

At the top of every forum page, there is a button called "FastLane". You can order TONS of parts for your car through there and help to support the resource that you have just found (MercedesShop.com).

Hatterasguy is correct, platinum plugs just don't work well in these engines. I have been there, done that and they don't work as well as the single electrode coppers. (A voice of experience)

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

I have an '88 260E that does the same and I was told that was not a spark plug but a fuel injector problem, also same, running fine then suddenly not taking off and stalling. Apparently I was told the injectors are worn and flood the engine, they are not expensive as far as the rest of the parts go, so get someone to check them, mercedes do have fuel injector testers!

The o2 sensor under the pas. side floor mat was wet sending false signals. The car runs like new now. Im still going to change the plugs though. My post above tells what I did to fix the wet problem. It was not the plugs though as first thought.

WasHappy..... Is still HAPPY!

Glad you're all fixed now. That O2 sensor probably caused the plugs to fuel-foul, they may be ok now... Btw, I agree with the others on good ol' copper plugs. The advantage of plat plugs is long electrode life, but most cars, especially older cars will foul them long before they wear. Usually oil fouling, sometimes deposits from fuel additives. Autolite is my brand.

I cannot see (in principal) why platinum plugs would not work on a Mercedes. They were wonderfully foul-resistant on my old oil-burning Renault. But....

The real problem is that the Bosch platinums seem to be only available in a resistor plug, and our 109E (and probably lots of others) needs a non-resistor plug. The resistors are in the plug caps. The Bosch listing ignores that, and lists resistor plugs as fitting our cars. Not so!

Really? I didn't know any car actually specified non-resistor plugs. I’ve used them on my chevy before just to try them, but they looked and seemed to perform no different than a resistor plug. I ran them with non-resistor plug wires which are illegal where I live so I had to try them.

The key to this discussion is the amount of resistance -- if you get wires and plugs matched to give the correct amount, platinums work fine. If not, you have trouble from excessive resistance and weak spark.

The only thing I've not had trouble with on the 280 is the platinum plugs -- I also have plain (non resistance) wires.

The O2 sensor not connected (or shorted with the heater wires, or a bad heater wire, whichever it was) probably carbon fouled the plugs. A few days driving will clear them and you will be fine.

I put Platinum +4s in the TE, they run just exactly like the Champion single electrode plugs I tested when looking for running problems (that eventually turned out to be a bad fuel pump relay).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!