CigarXO

W202 Community - I'll start a thread here, then broaden if needed as we are becoming a limited - though top quality - few...

1995 C36 AMG with 150k. Its been a few years since this car ran as an AMG should. Here's some history to help though most of this you lived through with me on threads & questions here. You helped tremendously!)

3-4 yrs ago: It started with CEL & P0104 (EGR) codes, a little rough idle. (I should say I had the wiring harness, catalytic and o2 sensors replaced several years before.) I cleaned MAS filter, temp sensor and tube. Only proved to be a temporary fix - replaced MAS filter/sensor with aftermarket product. (I know )

2 yrs ago: It ran rough and hot - replaced thermostat, water pump and all hoses. But, the hot temps and age had worn the manifold gasket, so I replaced manifold gasket, head gaskets, header gaskets, EGR tube, belt tensioner, spark plugs, had fuel ignitors rebuilt, replaced remaining belts/hoses and thorough cleaning of upper unit. I replaced all the tiny vacuum lines on top as I'd read that was a common source and true enough, most were cracked or aged. My INDIE smoke tested the car after I rebuilt the top end and failed to seat one of my ignitors properly. He's seen the car again in this last round, but didn't go there.

1yr ago: still ran sluggish after servicing top-end. Seemed to lack power in standing acceleration, slow to shift, and passing. (but my other vehicle is a Jeep 5.9er and I think I've been spoiled by its torque) Then, brake safety switch & NSS or something preventing start - so, replaced BSS, NSS, shift bushings, and had trans shop change fluid, filter, modulator/stage 2 something another...(don't have references in front of me.) Better, but still lacks aggressive shift on HWY. So, back to fuel,air,sensors...

This year: CEL & P0170 code. With my Indie who's been part of all this - we cycled the OBD codes a few times, but they return. He's only offering it may be cheap fuel??? I don't think he knew of cheap MAS filter, so I replaced cheap MAS with Bosch OEM. Code & CEL are gone, but idle is really rough - approaching stall and surge. I've disconnected the battery, driven the car a few times - no improvement. I don't want to go to the stealership or just start replacing parts by trail/error. I'm seeking your wisdom for next steps? Without codes - I don't know where to continue - o2 sensors,???

Current OBD reader is: No MIL (though it triggers the CEL during testing), 6 INC monitors (cat, evap, sec air, o2 sensor, o2 heater, EGR), 3 Ready(misfire, fuel, comp). Rough idle feels like its hunting with accompanying misfires. Again, no codes.

Thanks in advance!

CigarXO

Jasssc

I have been through the rough idle / misfire game for the past 2 years on and off, so I know your frustrations. First two suggestions
Did you replace coil packs when you did spark plugs? If not, do that. I would go ahead and replace sparks again, since it was 2 years and they are cheap, easy to eliminate that as a possibility.
I had a terrible misfire lately but no codes and the thing that just fixed my car was the injectors; a tech found the code stored in the ecu but never had a code for it, so I swapped these out and it runs like a champ now

ccrelan

I have been chasing a hunting idle for a couple years and have not really made any headway. I have replaced a huge list of things as well and the issue persists. I am going to look up someone with a Mercedes Star tool here very soon.

dearlove

Mine turned out to be my throttle body
wiring inside had completely disintegrated insulation, if you pull it off and just take off the metal cover you will soon see.

ccrelan

I have a mercedes rebuilt throttle and new wiring harness

CigarXO

Took a long enough trip to engage more of the monitors. The idle is still hunting, especially when cold after crank. I have noticed improved highway acceleration since the new OEM(Bosch) MAF installed. Yet, when I hit the throttle to engage the passing gear, I get an immediate response followed by a stall.

I got a CEL again - but, now no Codes???

So, today, based on someone's thoughts - I looked at the vacuum tubes. They all appear secure and no vacuum sounds when running.

I'm going to schedule a diagnosis with STAR.

ccrelan

I ordered the cables to use this software this past week. I am hoping to be able to sort out the issue using it.

http://www.hfmscan.com/en/mercedes_d..._kkl_soft.html

CigarXO

ccrelan -
Be sure to post your findings and if this cable and software helped.
Thanks,
CigarXO

ccrelan

My issue ended up being that there was vacuum to the egr at idle