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Old 04-21-2013, 05:29 PM
ehm ehm is offline
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Join Date: Sep 2006
Location: Lumberton NC
Posts: 49
Spark Plug Conundrum

I have a 2002 e320 with 131k. I am not a mechanic, and have done very little work on this car, but have replaced quite a few things on an older Lincoln I have (a different animal entirely). I decided to change the spark plugs on the Mercedes.
Initially I selected Denso 4503 / PK16TT, double tipped platinum plugs. I used the removal tool, did not pull directly on the wires, etc. All seemed to go (surprisingly) well. The check engine light came on when I started it after the replacement. Then, when I drove it, it stalled out at the 1st stop light. The pattern after that is it would almost stall out upon initial acceleration from a stop, and then take off fairly normally. It seemed a little less than optimum at highway speeds (like it didn't have everything it usually did to give).
SO, I did some homework, partially on here, and saw where some advised against the double-tip plugs, so I started over with NKG 7090 plugs (yes I am little bit frugal).
Much to my dismay - same thing; like as in no change whatsoever, right down to the check engine light. I will say with the Densos I reset the check engine light and it stayed off (but the driving symptoms remained); I have not reset it yet with the NKGs. I guess obviously I did not have anything like this before; the reason I changed them out is that I had a little rough idle at stoplights and just the mileage (don't think they'd been changed; not since I bought it with 84K).
Any thoughts on this would be welcome. PS- I do not have a code reader; I just reset the light by disconnecting the battery.

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Old 04-21-2013, 07:29 PM
RichardM98's Avatar
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Join Date: Oct 2007
Location: SoCal
Posts: 651
I've been using double tipped Bosch for about 4 years with no problems. I've seen the message you referred to. There's a lot of information on the Internet but not all of it is gold.

It's more likely that something happened during installation unrelated to the plugs. Some local parts stores (Autozone?) will read the OBD codes but remember they are in the business of selling things. An inexpensive code reader (<$50) is very handy. If you have a laptop there is something called ELM 5 scanner for about $25.

Clearing the codes/CEL by disconnecting the battery will only be temporary if the real problem still exists.
Good luck.

1998 E320 Wagon
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Old 04-21-2013, 10:56 PM
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Join Date: Jun 2011
Posts: 50
My guess is that some plug wires are not connected properly. They are an pain in the arse to connect properly; the directional force necessary to get them in place and attached to the end of the plug requires skill, patients and you really need "the touch" to know when it is right.
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Old 04-26-2013, 09:13 PM
ehm ehm is offline
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Join Date: Sep 2006
Location: Lumberton NC
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Thanks again for the responses on my stalling & check engine light after spark plug change. Here is what's happened since my last post; I got impatient waiting on the code reader I ordered from ebay, so I got a rebuilt (I KNOW, not advisable) MAF sensor; that's the only one I could find in town. No difference whatsoever; symptoms the same etc. Returned it and put original back on. (Also I rechecked all plugs and wires and for reasons that follow I really don't think there's any issue there).

So, code reader came today and the code was P0102. I found a thread, on here I think, about checking the #2 wire to the MAF plug, and I did that (I only have the $1.99 electrical tester with the light bulb) and sure enough the power appeared to be flickering in and out as I moved the wire around.

I cut open the rubber outer covering to see if I could at least use electrical tape to repair the troublesome wire, and they look perfect; all of them. Most recently I can't seem to get any sign of power to that 2nd wire at all.

When I looked at codes the last time I started the car, P0112 had joined P0102.

So it certainly appears the wire(s) to the MAF are the problem and I have no idea what to do about that. The harness seems unusually scarce online and I don't know that I'd know what to do with it if I got it (i.e. where are those wires would connect).

Do I just wave the white flag and take it in or does anyone have any other suggestions? I am a fairly decent shadetree mechanic but with wires of that size I am reluctant to do too much tinkering.

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