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Discussion Starter #1
hello , so i've always noticed that my car is underpowered and i always thought it was (( incert what im going to add later )) and nothing helped BUT few days back i started the car and hit the road quickly like within few mins of starting the car and when i hit the gas i wanted to accelerate a bit to avoid slowing down incoming traffic i was on a stop sign and started rolling and as soon as i hit like 20~30 km/ph i hit the gas like 25% and the tried just got LIT till i hit like 80~90 when it stopped it was the whole deal i got pushed back into the seat and all !! it was super responsive for few minutes i never had to hit the gas for more than 20~35% no need !! and then after like 10~15mins of drive the car went back to begin the car that i knew .... like flooring it with not even result in a wheel spin the rpm climbs sluggishly and even at high rpm the engine starts to cut off a bit like if it was misfiring AND there was MAYBE MAYBE at best 20% of the torque that i noticed earlier . now thats how my car always drives slow AF and loud too as in the exhaust sounds loud for no reason and i always thought it was for show . for the next few days i tried going hard as soon as i start the car and it was AMAZING like lighting the tires up till 90+ with MAYBE 50% gas with smokes and smells and the whole deal again few mins later the car is dead :< ... here is what i tried ever since owning the car to make it a bit faster ((( the cold start fast that it should be ))


1- i deleted the catalytic converter
2- resoldered the k40 (few times)
3- soldered the SC clutch to be always ON and checked the air valve and im fairly sure i even changed it once just to be sure
4- did the whole MAF relocating with new seals took the whole system apart and cleaned the oil and added an-oil catch the car did become a bit more torquey at lower rpm even after 10mins
5- changed the oil in the SC DAMN SMELL !!!
6- changed the transmission oil filter
7- new spark plugs and cleaned the fuel injectors
8- i fairly sure i changed / fixed all the small air pipes that looked that might have a leak in them
9- changed the fuel pump/MAF sensor few times original and aftermarket
10- resetting the transmission learning few times (((( EDIT ))))

im sure i did MUCH MUCH more over the years BUT nothing did an impact that i can notice only the relocating of the MAF and that was a minor impact . oh of course nothing showed up when i took it to the mechanics on the computer stuff like lights were burned and silly stuff like that only .... HELP HELP i want my speed back :crying: :crying:

it might not be the cleanest example out there but its my baby :<
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Discussion Starter #4
Guess A. Electronic Throttle Body or Electronic Gas pedal.

Guess B. Kompressor bypass valve is staying open.

Guess C. Intake vacuum leak

Guess D. Kompressor is no longer "kompressing"
like i said i tested and even replaced the bypass valve :> and as for the SC when i was relocating the MAF i forgot to tighten the nuts and i revved the engine and the pipe just POPPED open it scared the day light out of me :grin: so i guess its working fine :p as for the leaks i think i went as far as replacing a T looking valve (( was years ago :p )) on the back of the engine but thats as far as i went any ideas on how to check :> ?? also for Electronic Throttle Body or Electronic Gas pedal. how do i check ^^ ?
 

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Premium Member 1999 SLK 5.4 M113
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like i said i tested and even replaced the bypass valve :> and as for the SC when i was relocating the MAF i forgot to tighten the nuts and i revved the engine and the pipe just POPPED open it scared the day light out of me :grin: so i guess its working fine :p as for the leaks i think i went as far as replacing a T looking valve (( was years ago :p )) on the back of the engine but thats as far as i went any ideas on how to check :> ?? also for Electronic Throttle Body or Electronic Gas pedal. how do i check ^^ ?
sorry - didn't get all of it read! I just skim over things.

here's an idea. key in ACC, car off - have someone push the accelerator while you look down the throttle body (remove the intake tube). take note on how the throttle plate responds to movements in the pedal. When putting the key in ACC, the throttle will open slightly even with the car off. Now have them floor the pedal and see if the throttle opens up all the way.

Note: it may not open all the way with the car in N or P. You may even have to try it with the engine running.

I did this experiment when doing an engine swap earlier this year.
 

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Discussion Starter #6


sorry - didn't get all of it read! I just skim over things.

here's an idea. key in ACC, car off - have someone push the accelerator while you look down the throttle body (remove the intake tube). take note on how the throttle plate responds to movements in the pedal. When putting the key in ACC, the throttle will open slightly even with the car off. Now have them floor the pedal and see if the throttle opens up all the way.

Note: it may not open all the way with the car in N or P. You may even have to try it with the engine running.

I did this experiment when doing an engine swap earlier this year.
sounds easy enough ^^ thanks i`ll try it tomorrowz :>
 

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In your post you say 1- i deleted the catalytic converter
Will this not have a bad effect on this engine running with no CAT's causing the O2 sensors to incorrectly alter the mixture?
What do you think @Turdo2 is it possible to run without CAT's ?
 

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Premium Member 1999 SLK 5.4 M113
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In your post you say 1- i deleted the catalytic converter
Will this not have a bad effect on this engine running with no CAT's causing the O2 sensors to incorrectly alter the mixture?
What do you think @Turdo2 is it possible to run without CAT's ?
usually you'll just get an engine light. but it should still deliver "decent" performance. In fact, if he wouldn't of said he removed the cats, I would have thought clogged cats.

what stands out most is that he is getting full-throttle acceleration from 25% pedal :laugh:
 

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Lot's of different possibilities especially with all the mods. In the interest of starting out cheap and working your way up, try a smoke test for vacuum leaks (lots of youtube vids if your not familiar). Is your CEL on? Seeing any codes?
 

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Discussion Starter #10
usually you'll just get an engine light. but it should still deliver "decent" performance. In fact, if he wouldn't of said he removed the cats, I would have thought clogged cats.

what stands out most is that he is getting full-throttle acceleration from 25% pedal :laugh:
no dude if i hit it all the way to the metal i start to lose control and go sideways so i back off and go "slowly" :p trust me there is more xD
 

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Discussion Starter #11
Lot's of different possibilities especially with all the mods. In the interest of starting out cheap and working your way up, try a smoke test for vacuum leaks (lots of youtube vids if your not familiar). Is your CEL on? Seeing any codes?
no lights and the codes as i said are for little stuff that has nothing to do with drivability .
 

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Premium Member 2001 SLK320/2000 SLK230
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Well about here I'd be setting up Torque Pro to read and log a number of things like ignition advance, throttle position, forward O2 bank 1, same for bank 2, short term fuel trim for both banks, MAF, and RPM. Then go for a drive and check the logs. Something must be different when it acts normally and when it doesn't.

ps may need a 38pin to 16 pin OBD-II adapter but parameters should be available.
 

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If the cat is removed, the lambda sensors (O2-sensors) will give wrong data to the ECU. (No sensors, no data (voltage), no cat, wrong voltage). The usual hack is to use a circuit that sends the nominal "correct voltage" to the ECU.

Now, the ECU doesn't handle the cold engine the same way as a hot engine, and allow the sensors a lot of slack until the car is hot. Until then, it allows values outside the envelope, to help with Quick warmup and give good driveability. There is (most likely) a timer in the ECU for this to happen, after timeout, the ECU will be worried and goe into limp mode.

This alone may result in the symptoms you describe. However, there is seldom only one reason for problems like this.

If you don't get a CEL, i would make absolutely certain that you have a working lamp there. (It lights at startup, I know). With the symptoms you describe and the mod's you have done, I would expect codes to be thrown generously and lamps merrily alight ...
 

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Premium Member 2001 SLK320/2000 SLK230
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" There is (most likely) a timer in the ECU for this to happen" This is called "going into closed loop operation" and open loop usually lasts somewhere between 1 and 3 minutes before changeover (less when the engine is hot). This is mainly to give the O2 sensors time to reach 600 degrees F. I have never heard of one staying in open loop past 5 minutes and only if very cold.

This brings us back to needing instrumentation

One question needs to be exactly what was removed. You need the O2 semsors in front of the catalytic converter to work properly though the sensors after the CC are not supposed to move from midpoint so those could be substituted with resistors.
 

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Discussion Starter #16
Well about here I'd be setting up Torque Pro to read and log a number of things like ignition advance, throttle position, forward O2 bank 1, same for bank 2, short term fuel trim for both banks, MAF, and RPM. Then go for a drive and check the logs. Something must be different when it acts normally and when it doesn't.

ps may need a 38pin to 16 pin OBD-II adapter but parameters should be available.
i have that adapter but NON of my BT OBD2 readers can read the damn thing :<
 

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Sounds like the kompresor is 'kicking on at 2k' when in obd check engine mode as I experienced. Verses changing the k40 fixing those 'little check engine light' issues and getting smooth Kompressor operation through out the power band.
 

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"but NON of my BT OBD2 readers can read ". Are the lights in the dongle lighting up ? Dongles are powered by the OBD connector 12v..

I have a iCarSoft MBII i980 ordered that is supposed to be here on the 12th. I also have PC based scan tools. Both of these use wired (not BT) adapters that do not require OBD power.

That said my SLK is a '01 Facelift with a normal OBD-II connector under the dash with a mini BT dongle that works fine & while I have a 38 pin adapter, never have had anything to try it on.

Strongly suspect that one of these would be able to talk to your early model.

ps unless there is 12v between pin 16 and 4/5 the BT is not going to work.
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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I agree that 2-3 minutes is expected in "open loop" mode after cold start,. Most OBD2 scanners will report whether you are running in open or closed loop mode. Some "normal" things can cause your car to transition back to open loop after 3 minutes, it would be good to know which mode you are in when running "good" and "bad".

Is your ECU fan running properly?

The two pattern failures I think of here are 1)bad CKP sensor, and 2) bad transistor in the ECU.
 

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Discussion Starter #20
"but NON of my BT OBD2 readers can read ". Are the lights in the dongle lighting up ? Dongles are powered by the OBD connector 12v..

I have a iCarSoft MBII i980 ordered that is supposed to be here on the 12th. I also have PC based scan tools. Both of these use wired (not BT) adapters that do not require OBD power.

That said my SLK is a '01 Facelift with a normal OBD-II connector under the dash with a mini BT dongle that works fine & while I have a 38 pin adapter, never have had anything to try it on.

Strongly suspect that one of these would be able to talk to your early model.

ps unless there is 12v between pin 16 and 4/5 the BT is not going to work.
i get connected to it and all but the BT app always fails to connect to the ECU and i tried few of these BT ones :<
 
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