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1999 Mercedes Benz SLK 230 No power above 3K RPM P0170
Car has ABS fault (broken wires), hardtop inop, and a radio causing a 3A draw (temp. fixed). The other concern is the car runs smooth until about 3K or below about 1/2 throttle. After that is falls on it face and does not make power.
P0170 is stored. I've cleaned the MAF. It reads about 2.7g/sec on my OTC Nemisys in OBDII mode.
Fuel trims are LT 30+%, ST is around zero at cruising speeds. 02's respond within reason. Above 3K or half throttle the 02's go stupid lean and the car falls on its face. I saw the MAF around 56 or so when this happens.
Tested the fuel pump all OK electrically, 5.5A. Fuel pressure under load is 58psi. Only drops when you let off the throttle to around 46 psi.
I hear no or see no evidence of vacuum leaks which should make it run like crap at lower RPM's not higher anyway.
All injectors OHM at around 15.7. I need to bring home my UScope to run them tomorrow. I also want to do a injector/fuel pressure test to make sure they are flowing fuel.
I'll admit this Eurotrash is different but similar to US/Asian vehicles but different enough to be a PITA.
I suspect this is a pure fuel delivery issue and if the injectors check OK, I'm going back to the MAF. Any ideas or more info on the MAF, I have no access to any good data on it.
Also with the MAF, unplugged its worse. With the MAP unplugged its about the same.
Normally small engines idle at 3g/s. I'd expect this vehicle to idle around 4.5 g/s or more based on my experience. I just googled the code
www.obd-codes.com/p0170
. This is a case where a smoke tester in the intake system can really help. I'd think that either the MAF sensor is reading wrong or there is an air leak.
Getting involved in discussions because I have a lot to learn still.
MAF unplug test usually won't work on Mercedes, also Cleaning Bosch bead type analogue sensor will rarely show any improvement an it is not known to find either fake Chinese sensors or a an unsuitable Pierburgh sensor fitted in the original sensor unit.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Tested MAP senor and MAF again. All OK electrically. The MAF throws an odd scope pattern with revs. It not very linear at all.
Scan tool says 2.7g/sec on a hot idle. If that is too low then that is my issue.
In my experience displacement should about equal MAF g/sec readings at idle. This I have found to be true on most US/Asian vehicles.
I hunted for any kind of leaks with propane and found none. I do not have a smoke machine at home and I doubt I'll be borrowing one from work.
Give what you have written it sounds like I have a MAF issue. I've ruled out fuel delivery as the pressure, pump amperage, and injectors are all OK. I flow tested the injectors as well. All dropped 10psi.
I recently did a blog about
smoke effects for photography
but I think an insect smoker would be very useful for leak detection. Just use pure baby oil and you're away.
Getting involved in discussions because I have a lot to learn still.
Update. New MAF installed drove car. Runs great. I left my scan tool at work so I'll need to grab that to clear the CEL and run OBDII monitors but so far it looks good. I'd like to note the good MAF readings and I'll update those here.
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