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Discussion Starter #1 (Edited)
We had some trouble with our 98 slk230 the other night. She put gas in and 10 minutes later it dropped a coil. Misfire in cyl1 and 4. Replaced the coil and it was much better but not quite there. Then it cleared up after a few minutes of running.

Today, it threw another code. It won't rev out. It drives and accelerates good but if you give her too much throttle she chokes out and struggles...then it threw the check engine light again. I had it read and it's a P0170. They said a Bank 1 fuel trim fault.

What's going on here?
 

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2001 SLK 320(217K Miles), 2002 E320 Special Edition(183K Miles)
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Could be: (1) Bad Gas - Fill with new gas at a different station to dilute old (bad?) gas.
2) Blocked fuel filter - When did you last replace filter?
3) Bad MAF - Try and clean. Normally cleaning doesn't help much, but worth a try.
4) Blocked catalytic converter. Did you hear a rattle some time in the past when the car was idling?
 

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Discussion Starter #3
I've never done the fuel filter.

I checked my MAF a month ago and it was spotless...we've never cleaned it in the last 4 years. Maybe it just needs a good spray. I have the MAF cleaner already.

No rattle but she had to drive the car a few miles to get it home on 2 cyls.

This all happened a few minutes after she got a half tank of gas. I took it and filled it up the rest of the way at a different station.

It feels like a clogged fuel filter.
 

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98 red 230 slk
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Have you ever replaced the maf? Spotless means nothing. Cleaning only works for so long. P107 is prime maf problem.
 

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Discussion Starter #5
we've had it 4yrs and have never done it. The screen looked clean as can be and I can see no traces of oil anywhere in the tube.

it's easy, I can spray it down.
 

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Discussion Starter #7
why do we have codes when they don't tell you anything?

It throws a code and can be 1 of 20 things.....nice. Kinda like pointing towards a target and but not aiming.
 

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why do we have codes when they don't tell you anything?

It throws a code and can be 1 of 20 things.....nice. Kinda like pointing towards a target and but not aiming.
Not that simple. :D
Assume the O2 sensor reads that the mixture is too lean. Is it that not enough fuel is being injected or is the O2 sensor itself bad? Or is extra air leaking into the intake system? Or is the MAF sensor underestimating the amount of air passing?
Now you can pinpoint it more precisely for example by installing 3 MAFs and 3O2 sensors and accept the majority reading from each sensor area. But just think of the extra cost involved.
 
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