engine surge-"limp home" mode

kopy kat · 09-09-2008, 11:20 PM

yesterday as I was arriving at work in my '03 slk230 the engine started to surge. there was no throttle response, the car would move at about 20 mph. the trouble code shows as PO638....I can't find a reference anywhere for PO638. Any ideas?? help?? thanks, Larry

bazzle · 09-11-2008, 01:01 AM

Sounds like its lost throttle adaption.

Start car, put in drive, hold foot on brake for a couple of minutes.

See if idle settles down.

May also be connector on throttle or pots their selves.

Try cleaning the maf with maf spray as a long shot.

Seen similar faults on here. http://www.benzworld.org/forums/r170-slk-class/

kopy kat · 09-11-2008, 05:09 PM

Bazzle--thanks for the reply--I had to drive it several blocks in this situation--the throttle does not respond at all--just goes 20 mph. I did try the MAS cleaning--no difference--BAS/EPS lights stay on, CEL stays on---code still shows PO638, and even the MB dealer has no clue as to what PO638 is??

09-09-2008, 11:20 PM	#1
kopy kat Newbie Join Date: Feb 2003 Location: Reno Posts: 14	engine surge-"limp home" mode yesterday as I was arriving at work in my '03 slk230 the engine started to surge. there was no throttle response, the car would move at about 20 mph. the trouble code shows as PO638....I can't find a reference anywhere for PO638. Any ideas?? help?? thanks, Larry

09-11-2008, 01:01 AM	#2
bazzle Senior Member Join Date: Apr 2005 Posts: 374	Sounds like its lost throttle adaption. Start car, put in drive, hold foot on brake for a couple of minutes. See if idle settles down. May also be connector on throttle or pots their selves. Try cleaning the maf with maf spray as a long shot. Seen similar faults on here. http://www.benzworld.org/forums/r170-slk-class/ __________________ Melbourne Australia My car 1998 SLK230,R170, Cazzles car A class, 2006 W169 2 litre auto

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09-11-2008, 05:09 PM	#3
kopy kat Newbie Join Date: Feb 2003 Location: Reno Posts: 14	Bazzle--thanks for the reply--I had to drive it several blocks in this situation--the throttle does not respond at all--just goes 20 mph. I did try the MAS cleaning--no difference--BAS/EPS lights stay on, CEL stays on---code still shows PO638, and even the MB dealer has no clue as to what PO638 is??