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  #1  
Old 12-25-2002, 12:12 AM
Bruce B's Avatar
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POP goes the ??

I'm posting this for a friend of mine, told her of this site but as busy as she is...... Here goes: a '97 E320 made a "pop" under the hood yesterday then the "check engine" and "check engine elecronics" lights came on. Also has slower, rougher acceleration now. She had it in recently and the code brought up said "spark plug misfire". Any ideas? This is the lady I bought my Benz from and I know she would appreciate any help (perhaps even guiding the shop where to look for a permanent fix).

MERRY CHRISTMAS
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1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
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  #2  
Old 12-25-2002, 02:23 AM
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Are all six plugs intact or in the plug hole? I used to have a car that had one plug hole slightly stripped, on occassion the #1 plug would blow out. Not saying this is what she experienced, but it can happen. Also check all vacuum lines. I had one pop off near the fuel distributor, produced rough idle, poor acceleration and the economy gauge was always pegged in the red. Replacing the line on the nipple cure it all.
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  #3  
Old 12-25-2002, 12:36 PM
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OK, here is a story. It may apply here or it may not.

I thought about just writing a "fix" post but it seems to apply here.

My fun repair of the week was a 1998 E430. Fun repairs are those that breed fear and when completed bring the ultimate of satisfaction (very often with little monetary gain). The ticket said that the car lacked power and the check engine light was on and shifted poorly.

Upon driving the thing, the light wasn't on and mostly it drove fine. it did have some hesitation but the engine was warm when I started. Occasionally it would just quit accelerating under full throttle. So.. first step lets see what codes are stored. After a short test I had NO codes indicated for ME (engine management). There were codes in many control units ASR, BAS, SAM, ICM, ESLM (electric seat left and right I forget the acronym) and ACC.

I tested the ME anyway and there were stored codes for EGR, O2 sensors both sides, and P0170 and 173 adaptation codes. Based on the O2 codes and the adaption codes I checked actual values for adaptation. Lower partial was at 1.02, idle was at about .5ms. The 1.02 value was terrible for diagnostics as it is almost perfect. The .5ms is a significant mixture correction (adding fuel) but well within margins. The O2 sensors were slow but functioning well. It didn't make much sense.

The other modules all had CAN communications errors. The ASR didn't see the ME and the BAS didn't see the ASR and all the other modules had CAN errors.

Here is where the fear comes in. In the road tests the lack of power seems very easy to explain with a protective strategy based upon ASR / ME communications. Either a throttle position control or a timing control. This could be real trouble......After clearing codes and repeated driving, the network codes (CAN) did not reappear but the running was getting worse not better. The EGR codes reappeared and so did the adaptation codes while adaptation values maintained right around one 1.0(what can this be?). I had put aside my biggest fear by this time (an intermittant CAN short or control unit pulling the network down).

When in doubt try a AMM (air mass meter) which I would have by this time but I didn''t have a V8 one in stock.... so I get one coming for next day and we decide to remove the EGR pipe for cleaning while waiting for the next diagnostic step (the substitution of new AMM). My assistant is pulling the pipe when about 15 minutes later I hear one of those "How about that" screams. The first step to getting to the EGR pipe had been the removal of the formed hard plastic/flexible rubber intake (from the throttle assy to the AMM) pipe and there it is..... the flexible section is plastic clamped to the hard plastic and it ISN'T. There is a 3/4 inch gap at the bottom (the top is together or the repair would have been obvious). This pipe is one piece 30-40 inches long. The union of rubber to hard plastic is not servicable within MB procedures... the whole thing is on order,,, BUT a couple pieces of duct tape and some 5 in diameter tie wraps makes a virtual permanent repair and instant gratification to the diagnostician. The AMM came in next day (yesterday) and will join the others in stock (four total - 104HFM, 104ME, 112ME, and now 113ME).

There are two points to this story (maybe three). First is that directly, all my fault codes were leading me wrong. This is more often the case than otherwise. The majority of codes have no use for the symptom at test. Second is that this air pipe must be watched.. the car had recently had its pan resealed (at another facility) and the driveability came with the repair. and thirdly a functioning AMM does not directly indicate whether it is volumtrically efficient or correct. This one was in effect in the trunk, but it measured the air going across it (none) correctly and fourthly the engine management does an amazing job of taking care of itself. At any constant speed the car ran flawlessly by using its other inputs.
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  #4  
Old 12-25-2002, 12:51 PM
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<<(four total - 104HFM, 104ME, 112ME, and now 113ME). >>

This is the " MAS/ A to Z Diagnostic Tool"

I have a simular set in "OVP Format"
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  #5  
Old 12-26-2002, 01:18 AM
Bruce B's Avatar
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Location: east of Atlanta, north of Macon Ga
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*scratching my head* thanks for the post Steve, I'm running what you said through my universal translator....lol. So it seems that if the air filter is a little dirty the code will say that the tires need rotating and a light out indicator means the windshield needs cleaning, got it.....LOL. Just kidding. My friends problem could be any number of things eh? I'll pass this on to her tomorrow.
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1991 300SE (my ride, 279,000 miles, looks almost new
1954 Cadillac (21 yo son's car, he bought when age 15)
1972 SeaBird 19 ft runabout (old but solid, slant six, Volvo sterndrive perfect condition, undergoing complete overhaul and refit)
1998 Toyota Rav4 (my sons daily driver when he is in the Continental US, PROUDLY serving in US Navy)
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  #6  
Old 12-26-2002, 09:03 AM
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Actually you are real close to it (bg).

Where my story has pertenance to your case is my thoughts that you are describing an AMM failure; could even be the hose (something I might not of considered last week). The real key to diagnostics are the adaptation values. In most AMM failures the compensation is off the scale and is one of the codes.

I can tell you from personal experience that a lean AMM will cause misfire codes and this is real misleading, if one is diagnosing using codes.

After the fact, I can point to how the adaptation values in my case should have told me what was wrong (actually they did). Since they were both perfect (LP at 1.01) and at fault (adaptation fault codes P0170 and P0173) a loose hose was one of the possible answers.
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