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Issue when trying to rev

 
Old 08-16-2017, 10:41 AM
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2000 SLK230
Issue when trying to rev

Hey there, relatively new to SLKs and the one I have is having a small issue (only got it about a month ago and its always had this problem).

If I put the hammer down it can't rev past 4000 rpm (and doesn't shift out of first, If I take my foot off the gas and ease back into it it'll shift into 2nd shortly after 2000 rpm like usual) it also hesitates on its way to 4000 and theres some 'popping' heard from the exhaust not sure if that's a backfire or misfire or what. If I try a couple of times to get it past 4000 rpm the whole engine block will start to shake enough that the car can be seen shaking and when I hit the gas (more gently now) the car sounds like a diesel, if I shut it off and turn if back on the engine shaking and diesel noise goes away.

I can also smell unburnt fuel if the car runs in my garage (with the door open, obviously!)

I have done the following to the car;

1. Clean MAF (it wasn't very dirty to begin with)
2. New fuel filter
3. New oil
4. Clean throttle body (that was actually kinda dirty)
5. New spark plugs
6. New camshaft sensor
7. New crankshaft sensor
8. New air filter

Not sure if this helps or not but I also had a rad hose replaced by a mechanic and he didn't fill the coolant reservoir right to the top, when I drove it home (3 minute drive) the engine behaved the whole way like I was revving it high; it shaked even though i was very easy on the gas and it had problems shifting if I went over 2000-2500 rpm. I noticed the coolant level was a little low so I added some distilled water to it (full now) and the water took care of the problem at the lower rpm range.

Theres no leaks on the car and all the plugs have spark.

I was thinking that maybe it's misfiring when I try to push the engine and then that throws the whole engine out of sync when I return to normal driving, resulting in the shaking and the shaking disappearing when I start it up again (fresh start). But I fail to see how this could be related to the very similar issue I had with the low coolant level... maybe it's not. Clearly I'm not a mechanic.


My ideas are:

1. Replace Fuel Pump
2. Replace Fuel injectors
3. Replace K40 (it looked fine but maybe there is some minor fault with it I couldn't identify)
4. Replace wires/coils
5. Replace distributer
6. Bad cat converter?

I think I'll check for a vacuum leak tonight to start though.

I might run some seafoam through it too to see if cleaning the engine helps at all.

The car also has 84,000km on it, no check engine light, can't read codes on it either (nothing to plug into).
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Old 08-16-2017, 10:46 AM
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2000 SLK230
Originally Posted by Gorak92 View Post
Hey there, relatively new to SLKs and the one I have is having a small issue (only got it about a month ago and its always had this problem).

If I put the hammer down it can't rev past 4000 rpm (and doesn't shift out of first, If I take my foot off the gas and ease back into it it'll shift into 2nd shortly after 2000 rpm like usual) it also hesitates on its way to 4000 and theres some 'popping' heard from the exhaust not sure if that's a backfire or misfire or what. If I try a couple of times to get it past 4000 rpm the whole engine block will start to shake enough that the car can be seen shaking and when I hit the gas (more gently now) the car sounds like a diesel, if I shut it off and turn if back on the engine shaking and diesel noise goes away.

I can also smell unburnt fuel if the car runs in my garage (with the door open, obviously!)

I have done the following to the car;

1. Clean MAF (it wasn't very dirty to begin with)
2. New fuel filter
3. New oil
4. Clean throttle body (that was actually kinda dirty)
5. New spark plugs
6. New camshaft sensor
7. New crankshaft sensor
8. New air filter

Not sure if this helps or not but I also had a rad hose replaced by a mechanic and he didn't fill the coolant reservoir right to the top, when I drove it home (3 minute drive) the engine behaved the whole way like I was revving it high; it shaked even though i was very easy on the gas and it had problems shifting if I went over 2000-2500 rpm. I noticed the coolant level was a little low so I added some distilled water to it (full now) and the water took care of the problem at the lower rpm range.

Theres no leaks on the car and all the plugs have spark.

I was thinking that maybe it's misfiring when I try to push the engine and then that throws the whole engine out of sync when I return to normal driving, resulting in the shaking and the shaking disappearing when I start it up again (fresh start). But I fail to see how this could be related to the very similar issue I had with the low coolant level... maybe it's not. Clearly I'm not a mechanic.


My ideas are:

1. Replace Fuel Pump
2. Replace Fuel injectors
3. Replace K40 (it looked fine but maybe there is some minor fault with it I couldn't identify)
4. Replace wires/coils
5. Replace distributer
6. Bad cat converter?

I think I'll check for a vacuum leak tonight to start though.

I might run some seafoam through it too to see if cleaning the engine helps at all.

The car also has 84,000km on it, no check engine light, can't read codes on it either (nothing to plug into).
Maybe the tranny fluid is low too?
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Old 08-16-2017, 09:32 PM
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Tonight I took a look at the fuses and found that the fuse for the coils was 15 when it should have been 10 (15 is for the 6cyl while 10 is for the 4 from what I could find on the internet), so I put a spare 10 in and took the car for a ride around the block. And the issue is still there but it change a bit...

After trying to rev hard while driving (gas fully depressed) it still sputters a bit and the SC will engage and I can hear it whir, however the RPMs will be at about 2k and the engine is definitely not firing correctly. If I hit the gas lets say 66% the car will sputter for a bit until there is a backfire and then the engine resume normal operation. If I hit the gas all the way, RPMs drop to 2k while the SC whirs and then when I take my foot off the gas the engine engages and I think the RPMs go up but I cant tell because the two times I've done that tonight the car slows down hard when I take the foot off the gas.. tranny downshifting hard I think... enough to make me lurch forward so I didn't want to try that again.

The good news is that after trying that a couple of times the engine no longer sounds like a diesel and the engine wasnt shacking... so half of the problem gone I guess (or maybe its still there, who knows)

Also, I tried removing the plug on the MAF and running the car to see what would happen and it ran for about 5 seconds with the SRS light on and then the battery light illuminated and then all the lights illuminated and the engine died. Plugged it back in and it ran fine.

I think I might try changing the coils? Maybe clean out the PCV?

Any ideas? I am open to suggestions...
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Old 11-13-2017, 11:33 AM
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I didn't see a solution so I'll post my experience with roughly the same symptoms:

The car would start but when throttle was increased it would stumble, stall, rattle, and everything else but run normally, I notice you mentioned radiator hose, could be a clue(wink). My issue was a MAF shorting out. Somehow water was sitting in the intake tube from the supercharger over to the MAF, the tube runs under the radiator. When idling it would run somewhat fair but once the throttle increased the problems got worse. Cleaning and inspecting the MAF is not the way to diagnose by the way. After several starts and stalls and cleaning the MAF I pulled the MAF out and I noticed moisture so I started the car with the MAF not connected to the tube(off to the side) and when the RPMs increased I got a face full of water.
I cleaned out the tube and replaced the MAF sensor, which was shorted from the water , looked clean though. I can see others getting into the same situation and if you try it enough times you'll blow all the water out and never find the problem, just replace parts until it happens again. As these cars get older I'd suspect more leaks in that tube/seals and possible water contamination.

The bottom line before replacing all these parts and throwing money out the window, try to get a handle on the situation, all of those sensors could have been checked with a simple meter before replacement.
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