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1998 A Class 160 Petrol w168
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90 Posts
Discussion Starter #1
Hello. I have a problem with my 1998 w168. Sometimes when I start the car in the morning or if the climate changes (example more cold), the revs will go up and down until it stabilizes. Also if I don't wait stabilization after powering on the car will hesitate when accelerating.
I don't have any error stored in the ecu.
Lambda sensor is new, spark plugs are new, mafs was repaired and rebuilt last summer.
Fuel trim adaptation tells more or less Upper 1.1 Lower 0.9 I don't know exactly what this means.
I don't get a very good mileage, 13 litres will last 120km more or less.
I was told maybe a vacuum leak but I can't find any or see where it could be.
Any clue ?
 

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Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,221 Posts
I follow forrera’s advice and never, ever drive without warming up for 60 sec (longer in winter). But if I did, I might experience the same symptoms.

What’s the rush? And if your wife’s in labour, who cares about a bit of hesitation?

Let the ECM warm up and make its adjustments. It is designed to run rich on cold start, then reduce RPM according to coolant and intake air temp (I guess).

How new is your air filter?

Did you have a MAF sensor code? What was wrong with it? New MAF is always better than repaired/rebuilt/cleaned-previously-dirty MAF.
 

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Registered
1998 A Class 160 Petrol w168
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90 Posts
Discussion Starter #4
You can’t replace the maf alone. It’s welded onto the ecu. Actually I experience some hesitation even after warming while changing gear. The air filter is brand new.
 

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Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,221 Posts
Thanks.
Actually I experience some hesitation even after warming while changing gear.
If it still plays up when warm, I suggest posting a video to YouTube showing the issue, and link to it here.
 

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Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,221 Posts
You can’t replace the maf alone. It’s welded onto the ecu.
You can’t replace the throttle valve alone either. So I replaced my ECU with it. Along with the MAF. Plus I had to replace my immobilizer module. Because you can’t replace the ECU alone. And I needed to replace my key fobs. Because you can’t replace the immo unit alone. But I kept my old door lock barrel and ignition lock. Kept the old key blades.

Moral of story: If your MAF goes bad, there are a few dominoes to deal with.
 

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Premium Member
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,221 Posts
From c.2000 they assembled the ECU with the throttle valve/body instead of the separate components in MY98-99.

This change continued for the rest of the W168 series.
 

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Registered
1998 A Class 160 Petrol w168
Joined
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90 Posts
Discussion Starter #9
From c.2000 they assembled the ECU with the throttle valve/body instead of the separate components in MY98-99.

This change continued for the rest of the W168 series.
Ah ok.
I have the 1998 model.
 
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