CopperDesigno

Guys,
Any idea what these codes mean in english?

P1420 - Mfgr control Auxilary emissions control
P1525 - Mfgr control vehicle speed Idle speed control Auxilary input
P1235 - Mfgr Control Fuel Air Metering
P1236- Mfgr Control Fuel Air Metering

Thanks
Greg

bazzle

Better desc:

P1235 Supercharger function
P1236 Magnetic super charger clutch
P1420 AIR pump switchover valve
P1525 Adjustable camshaft timing solenoid

Whats happening?

Bazzle

CopperDesigno

Bazzle, where did you get those descriptions, they are better then the ones that came with my code scanner.

The problem with the car is that the check engine light comes on. The car runs fine sometimes, sometimes it seems to be running like crap, no power.

So if I had to take a guess, I would say the pulley clutch for the s/c is bad.. which may be throwing the other sensors off .

Thanks Bazzle.

mjcother

I think you may have something similar to what just happened to me... car intermittantly runs like crap, now is 100% anemic...

Start the car, open the hood, activate the throttle sensor, which is thing the throttle cable is hooked to. You should see the real throttle body move in unison, and watch the supercharger clutch... mine just went bad, it turns about a third of a revolution before stopping again, but spins freely by hand... clutch appears to be toast...

Anyone know what is involved in replacing this? what kind/size of puller is needed, can it be replaced without removign a lot of crap, etc? I am a good mechanic, but would hate to ruin something learning by trial and error ;-)

also, while poking around in the area of the supercharger, I noticed my PCV bottom hose was all gooey, and had a small crack, which became a tear when I touched it...

-mike
Clearwater

CopperDesigno

That sounds about right with what mine is doing.

I'll have to poke my head in there and figure it out.

Thanks

mjcother

New update.... being Christmas Eve and wanting to cruise around with the top down, I decided to see if there was a quick fix for mine...

I pulled off the belt, then gently grasped the outermost part of the pulley with a big set of channellocks *gasp* and loosened the 8mm head bolt and removed it and the outer cap on the pulley....


The pulley and cap have a mating/friction/whatever surface, and there is a gap between them. In addition to some slight wear, I noticed a slight film on the surfaces, so I cleaned them with brake cleaner and reassembled, hoping for a tempoorary miracle, but there was no change..

I removed the cap again, but left the belt on this time, as it is not needed for just removing the cap.

There were 2 thin washers used to set the gap, each was 0.015" thick, and I had a little more gap than that, so I assembled with one washer only, and there was slight drag, but I hoped the closer proximity (smaller air-gap) would dramatically increase the strength, as magnets do... this did not fix the problem either, so I put the other washer back in...

I think my problem is within the inner part of clutch or in the signal telling it to lock up... I measured the resistance of the clutch coil, and it is 3.2 Ohms (4.0 ohms, but digital meter reads .8 ohms with leads touched together)


There looks to be a snap ring holding the pully on to the inner, stationary part of the clutch, but my right angle snap ring pliers are in Vegas with my jeep, so will try to find another set to pull the pulley off and have a look at the inside... I sure hope there is room to pull off the pulley without removing the intercooler manifold from the supercharger...

-mike

mjcother

while digging around, I found that the connector to the air bypass valve was nearly off... I connected it, and the pulley started working in the garage, but car still runs like crap... I pulled the hose off the bypass and blipped the throttle, and saw the butterfly close and re-open when the supercharger cut in...

I guess a possible next step is to verify the clutch is working when under load... maybe the PC interface for the computer would be handy to see the boost and other stuff...

well, I am learning a bit, I guess :-)

-mike

CopperDesigno

Nice work MJCother.

Where is the air bypas valve located?

mjcother

this thread has a nice pic with arrow...

https://mbworld.org/forums/slk-class-r170/132196-slk-supercharger-gone-bad.html


also, I pulled all the modules out of the ECU compartment, and the small one towards the driver's side of the car seems to be the k40 relay module they are talking about, but I had no bad solder joints... but now after all that messing around, I have the ASR and ABS idiot lights on....


-mike

bazzle

Pull maf sensor out and give it a spray of maf or contact cleaner.
Remove NEG batt terminal for 30mins to remove all codes.
(have radio code 1st)

Bazzle

mjcother

I removed the batterry negative terminal for an hour, and the ASR and ABS ligfhts stayed on, I disconnected the battery and re-seateded all the connecters in the ECU box(all looked fine), and left the batt ground off for another 30 min, the lights were still on, but a few starts later they were off...

on the MAF - I had replaced the MAF about a year ago due to stuttering, and cleaned it a few weeks ago when the car started running crappy... always seems to be a light film of oil on it... anyway, the car was noticably rich to the nose if I held it wide open in park, and it would "bog - rev a little - bog - rev a little".

I had my OLD MAF in the garage, I put it in, and the car revved good after it cleaned out, ran good for a minute, then started the stuttering and backfiring for which it was replaced, but the immediate, off-idle deadness was gone......

I guess it is another $350 MAF...

Buellwinkle

The easiest way to know if you need a MAF is to disconnect it. By doing so the car runs on a fixed set of mappings and will throw a code saying it can't communicate with the MAF but that's OK. Your car should then run fairly close to normal and a lot better than with a faulty MAF. If your car still runs poorly, it's not the MAF. Also, if your MAF is getting contaminated often, then the problem is clearly before the MAF, a check valve, aftermarket filter, factory filter with hole in it or not seated properly, etc. Also, remove everything prior to the MAF and clean it well with a good degreaser.

David in OZ

Mike.......re MAF "always seems to be a light film of oil on it... "

In your first post you said 'I noticed my PCV bottom hose was all gooey, and had a small crack, which became a tear when I touched it... '

This is really an oil separator.....it has a reputation of not being very efficient if not well maintained .......the bottom hose takes the separated oil to the dip-stick tube and back into the sump........

Give the separator a good clean out and check all hoses......this might not be your total problem, but important when you consider the cost of a new MAF.....cleaning your old MAF should last a lot longer without it being subjected to an oil spray

Oil Separator check/clean should really be added to a 'B' Service

Hope this helps

David

mjcother

I had cleaned the separator with brake cleaner at the time I noticed the bad hose, I wondered if it was a separator or valve, as the cleaner came out all orifices... the bottom hose I replaced with some good tubing, but planning on ordering all three hoses new, as the upper ones are hard.

I unplugged the MAF (the one replaced within the last year), the car died the first time I started it, but then started and ran 90% as good as normal when driving around the block (slight hesitation is all). I shut the car off, plugged the MAF in, started it, and it idled well, but ran like crap off idle, not even revving in park... I disconnected it with the motor running, and it went back to 90%, I plugged it back in with the motor still running, and it ran like crap off idle.. I guess I will be ordering new MAF and hoses and hoping there is not a lot of oil in the intercooler :-(

thanks all, for your help...

-mike

David in OZ

The Oil Separator is quite an ingenious design.......but does rely on having the supply of compresssed air from the supercharger( 2b...thin tube on my 1997 SLK 230K)...this can block fairly easily, especially the plastic injector nozzle at the join to the large tube(2a)

I know it sounds like a difficult dirty job, but I think it would be wise to clean the intercooler....I've never had to do it, but I imagine yours would have some oil sludge that could continue to cause problems

Cheers

David

DesignoSLK

Great illustration/description David! I think though, they made a slight mistake in the last paragraph by refering to the oil as item "B" when it was previously "A". However, it shouldn'y really lose anyone on the concept.