Re Soldered the K40 module now rough idle/running and no power

[techcareuk]

ok, ever wish you hadnt started something?

ive had an intermittant prob of lack of power on accelleration occuring few times a week and getting worse.

I suspected the K40 soldering problem but also ordered a new MAF.
I fitted the new MAF at the weekend and it didnt improve things so I pulled the K40 relay unit out and yes a nice big dry joint in the usual place on the connector to plug A, also noticed much of the soldering on the board looked like it was going dry so I re soldered the whole board and re installed it!

now when i start the car it starts and runs fine for about 3-5 mins then idles very rough for couple mins then switches back to idleing smooth and this dance continues.

on driving the rythm continues and when running rough there is virtually no power, strugles to get over 2k revs and when in a smooth phase it runs almost normal with much more power and revs are back up but still not perfect?

pulled the K40 module back out and inspected and double checked the soldering but visually everything seems fine

does anyone have any ideas
Thanks
Mark

 

[Auto-mobile]

What brand maf did you fit? Sounds more likely a problem with that.

 

[grober]

Which of the many fine automobiles you list in your profile are you talking about?

 

[John Jones Jr]

Have a look here, it just about covers every aspect of Kompressor problems.

R170 SLK Class - Mercedes-Benz Forum

 

[techcareuk]

Auto -Mobile,
Not sure on MAF make, its un marked but the old (cleaned) one is installed now.

Grober,
Its the SLK R170 this fault is about!

John Jones,
Thanks I have already posted this there too!

 

[techcareuk]

bit of progress and more questions...........

ok think im making some progress........

I removed the K40 and checked the relay contacts and operation, all relays energised fine when 9v was applied to the coils but 3 of the relays showed open ciruit on the N/c contact of the relay so I removed the common contact on all relays and cleaned the contacts on it and the relays, I re assembled and checked the contacts for continuity again, all seemed fine, sprayed some switch clean lube and instaled again!
to my dismay no difference but ive noticed a couple of things, there is no IGN (alternator ) light or oil when the IGN is turned on, when started it now idles ok for a good 5 mins then becomes rough, if you rev very slowly it will climb the rev scale to about 2.5k ish but then starts coughing, looking at the supercharger the clutch on the pully tries to energise as i try to rev but it doesnt seem to be getting enough current and the coughing coinsides with the clutch failing to spin the supercharger!

So then, does the K40 apply the current to the supercharger, if so can anyone tell me which pin numbers on the K40 do the wires from the supercharger clutch connect to it?
if its not the K40 that drives the S/C clutch where is it driven from??

This is screaming dodgy relay contact to me!!!

 

[John Jones Jr]

Can't help on the wiring but the K40 does control the S/c clutch according to several members on that U.S. site. And from what I've read up on, all of their problems were caused by either a faulty K40 or a blown Mosfet in the ECU.

 

[techcareuk]

Thanks for confirming the K40 controls the s/c clutch, any idea which relay in the k40 or which plug& pins

just removed the k40 again, double checked the relay contacts for continuity and refitted, now the sc clutch wont even try to engage, AGH!

 

[martyz]

If the MAF is not Bosch,then change it,if it is they don't like being cleaned either.

 

[John Jones Jr]

Thanks for confirming the K40 controls the s/c clutch, any idea which relay in the k40 or which plug& pins

just removed the k40 again, double checked the relay contacts for continuity and refitted, now the sc clutch wont even try to engage, AGH!

Again, I can't help as my C230K has a different K40 to both yours & the CLK. Personally, if I had an SLK with your current issues I'd buy a new K40 regardless along with checking the op of the cooling fan too while you're at it. Have you read the codes yet?
I ask because a faulty cam position sensor will cause the S/c to go inop on your car. And it's another part I'd replace also if it looks original, because simply put, it will fail.

 

[techcareuk]

Ok everyone here is an update to where i'm at -
Managed to get PDF's of circuit diagrams from 'Subby' on another forum!
also at the end you will see this eve I took Martyz's advice and removed the unbranded MAF!

---------------------
ok, looking at the diagrams, the K40 provides +12v via circuit 87 to the SC clutch and the clutch is released by a feed directly from the N3/10 via plug F pin 21

Ive measured at the clutch socket and correctly have around 14V when running at pin 1 but when i rev the car the N3/10 does not appear to be applying 0V via plug F pin 21?

checked continuity of the cable back to the N3/10 and everything is fine!

if I build the revs up slowly the SC does not try to engage after 2k revs and the engine dies!
BUT i've found today that if I aggressively pump the throttle and build the revs up like that the SC tries to engage for split seconds at every pump and I can build the revs up to 3k + ish, the engine runs like a dog and sc spins slowly from the constant engage attempts

so my thoughts are the N3/10 may be missing a signal from somewhere and not allowing the SC to engage???
Any ideas what would stop the N3/10 from sending the signal to release the SC clutch when it should?


I have got the matches ready now because this is really doing my head in now!!


forgot to mention, i've applied 12v to the clutch directly and it operates fine!

an update!
I soaked the old Bosch MAF sensor in Isopropyl Alcohol (thought I had nothing to loose) and removed the new OEM one i'd fitted earlier this week and fitted the Bosch one back on the car.
started it and opened the throttle, it ran like a dog but the supercharger clutch engaged the way it should, rev'd it for bit and the roughness seemed to get bit better (only a bit though its still as rough as a dog!)

left it idling to get up to temp and took it for a run, when accelerating it started to die, best way i can describe the effect is as if the spark plugs where crap.....
took it for a run on the motorway for few miles and it stayed the same running rough on acceleration but running smooth-ish when cruising?

think this has got me beat now! :-(

 

[Auto-mobile]

If you don't think it's the maf, buy yourself a secondhand k40 with same part number.

 

[techcareuk]

really not sure about anything now?
feel like i'm on wild goose chases in different directions.

think i may have to buy a Star Multiplexer and see whats going on...........

 

[techcareuk]

OK, thought i'd post an update and let everyone know what caused this!

turns out the root of this problem was faulty cam sensor and faulty MAF sensors (both the original one and the new after market one showed the same dodgy readings!!!) and to make sure the day didnt get dull the exhaust manifold has a leak so the 1st O2 sensor isnt getting the correct readings!

glad the wild goose chase i was on is finally over!!!

 

[jibcl500]

Did you check for oil in the loom from the cam adjustment magnet? this can follow through to the engine ECU and allow the plug to get wet with oil.

jib

 

[techcareuk]

yes, slight leak but not wicking up the loom, I'm going to solder the wires as suggested to stop the path!