1997 SLK 230k auto. Missfire after 1800rpm

[slippy]

Hi well I have today borrowed a known working MAF....still got the issue..so not that

I was told by the guy who did mine that my MAF was ok but still worth a try. Can you borrow a working cam sensor magnet too?

 

[Remote11]

I will see if I can and let you know, I am a bit worried that yours has been on star and its not been identified

 

[Remote11]

Im also reading it could be crank position sensor as this can cause this but won't always show a code so I will try and borrow that also

 

[slippy]

The guy I went to didnt have STAR, I only have his word that a friend of his at another garage has used STAR on it so I dont know for definate unfortunately.

 

[slippy]

Ive just discovered the Cam sensor magnet is also called the Camshaft position actuator (CPA)
After a very quick search it seems that the CPA doesnt do anything until a certain amount of revs then it recieves a signal & advances the timing??
Im thinking this new part may be the cause of the problem? Or the CPA is not getting the signal due to faulty wiring???

Am I barking up the wrong tree???

 

[Remote11]

Are you on about the round device under the black cover on the front of the engine?, as I looked at mine earlier and its bone dry under there, unplugged it and there was a minute amount of oil on one of the connector pins, cleaned it...no different, I also looked at the cam position sensor at the front of engine just behind the black cover on the pass side of engine again give it a clean no different....I gotta get it to the star man before I put a sledge hammer to it
its the scary drive worring me as its all main roads very busy..They are open on sundays so Im hoping I can be a true sunday driver and nurse it to him with out causing an accident! really getting on my last nerve now

 

[slippy]

Yeah, the round thing under the front plastic cover, held on with 3 bolts.
Aparently it doesnt have to leak, it can just fail, although leaking is the main fault of it appaerntly.

This sensor kicks in at about 2000 rpm & advances the cam timing, it then retards the timing over 4000 or so rpm.
I assume if this fails, the plugs will still fire, but at the wrong time, throwing up the missfire codes? When the ignition is turned off, everything goes back to normal.

All the above is what Ive just discovered over the last couple of hours, sounds promising.
Good luck with yours mate.

 

[Remote11]

Hmm you may be right...still going to get it stared first to confirm...perhaps the oil on mine has caused it to fail... but I thought you said you have changed yours are you thinking the new one is a dud also...

 

[slippy]

Yeah, it is a new one from inchcape mercedes. Only changed it because of it weeping oil slightly from the bottom, I didnt want it to get worse & cause any problems.
Funnily enough.....Ive never had a problem in almost 3 years until I changed this!!!

Unfortunately, after I fitted the new one, I fired the car up & all seemed well so I threw the old one away.

Im going to get the car back from the garage on Saturday & try a new one I think.

 

[Remote11]

it's mad I have read posts from all over the world with the same issue we have but not one of them has concluded with anything...the weekend could see 2 of us actually posting that conclusion in one go eh... all the best pal.. I will keep you posted on progress

 

[slippy]

I collected the car, drove it home VERY slowly then went to the Merc dealership in Doncaster in the Jag to collect another Cam magnet / Cam position actuator whatever you want to call it. Fitted it & still have the problem. It is very slightly better, sounds like its running on 3 cylinders now not just two but now there is a slight trace of mayo on the filler cap. Is this Head gasket failure or just condensation as the car has been started & stopped over & over in the last 3 months & not driven anywhere?

Very frustrating..........

Over to you!!

 

[Remote11]

I would say that's condensation to be fair...I have not managed to get mine to the star man as yet will have to try this week, looks like you are going to have to bite the bullet and get it plugged in for a proper going over....I thought you would be sorted after the 2nd magnet....(scratches head)

 

[slippy]

Unfortunately Ive not had chance to do anything with the car since my last post as the liner in my Koi pond has decided to split so I have been busy trying to get on top of that........If its not one thing its another eh?
Im going to try a new fuel filter next I think, just incase fuel starvation is causing the initial missfire & this is causing the ECU to shut down the two cylinders???
When I do get around to the car again, I will post an update.

 

[Remote11]

hi you had any joy with the slk?

 

[slippy]

Hiya mate.
No, not had chance to do anything with it as yet. Cant afford to get it to an indi for a proper check out so Im testing the water on ebay at the moment. It ends today actually in a couple of hours.
You had any joy yet??

 

[Remote11]

no I haven't either, as im not using the car at the min im delaying the drive to the indi.. but will need to sort it very soon as I need to be back on the road

 

[slippy]

Not been able to do much recently due to going on holiday but a brief update just incase anyone else comes across this problem & wonders what the cure is, well so far, for me, there isnt one -

2nd new cam sensor magnet tried......no change.
New MAF tried......no change
ECU removed and sent for testing......ECU is fine, no issues.

Ill report back if / when anything changes.

 

[slippy]

Another auto electrician / diagnostics guy walking away scratching his head.

This one thinks because the missfire sometimes starts at 1500 rpm, sometimes 2000 rpm plus, sometimes it does not missfire at all especially on tick over or if its revved really hard........faulty / clogged injectors?

Or timing chain slipped ?

Other than that, no more ideas.

Is timing an expensive / lengthy job?

 

[flango]

Another auto electrician / diagnostics guy walking away scratching his head.

This one thinks because the missfire sometimes starts at 1500 rpm, sometimes 2000 rpm plus, sometimes it does not missfire at all especially on tick over or if its revved really hard........faulty / clogged injectors?

Or timing chain slipped ?

Other than that, no more ideas.

Is timing an expensive / lengthy job?

Pretty sure it won't be timing, have you tried this guy? He's local to you and used to do all our scoobies, cosworths etc. If its electrical he'll find it for sure

Mobile Auto Electrical company covering South Yorkshire est 1998

At least it would rule out if it was electrical or mechanical for you

 

[slippy]

Thanks for your reply Flango.
Thats the first guy I had out. He couldnt figure it out but when he left after about 2 hours it was running but the day after it was back to normal & I didnt get chance to drive it anywhere.
Thats what it does, it lets you think is ok but turn your back on it & it sticks two fingers up at you!