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Bad throttle hesitation

9155 Views 12 Replies 6 Participants Last post by  jbanks15
Good Day....My head scratcher is a 1997 SLK230 RH drive....I have searched and searched and have found quite a few suggestion on this issue, however I have also found on the threads that a lot of people have got no real solution to the problem. So I have a few questions now and any help would be great and hopefully start me down the right road. First off I am showing no CEL but the light does come on when I start the car so I'm pretty sure it's not the bulb. I have not got the 38 pin cable adapter for my OBDII reader yet so I cannot check if any codes are showing up. I will be doing a complete service this weekend because I just bought the car and it's just a habit of mine to do this with every car I buy right off the get go just to make sure. So it's getting new air, oil, fuel, cabin filters as well as new oil...Q1. Any recommendation for best oil for these engines?? But the problem is...If I put the throttle right to the floor I get a big lag like it going to stall then a slow climb for about 1000 RPM then it just starts to drop off the RPMs and will start to sputter. If I just ease on the throttle it will climb all the way up. If I go to manual shifting and keep the RPMs around 2500 - 3000 it will respond fairly fast and usually not sputter. I disconnected the MAF and it had no change but this time it almost stalled at idle after a full throttle application. In addition to that it doesn't feel like it down shift when you give it a full throttle application while driving to say pass another car. Acceleration is about 0 - 60 in about 11 sec a far cry from the 7 sec it is suppose to be able to do it in, It seems like the tranny is stuck in winter mode. Has anyone heard of this being an issue before? I am going to do all the checks during the service just to be sure MAF, K40, Vacuum lines. Any help would be great, otherwise I will let you know how all this goes....Cheers
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I say, see how it goes after you give it your one over. Replace the plugs too, easy enough to do on the 230.
I think Chris has called it, wait until you've done your service. Apart from new plugs, check out the cleaning the MAF threads and youtube links.
I'm waiting for warm weather but will be doing that one myself. It looks straightforward (couple of clips and an electrical lead then electrical cleaner aerosol).


Being stuck in Winter could be as simple as the electrical connection. There's several R170 centre consul removal threads.


Dropping a gear is the best method for harsh acceleration. Ours is sluggish for a fraction before the software catches up with the planned overtake without the gear change.


Straightforward and simple often proves to be the best way to approach R170 issues. Not just my experience, but also reading other folks troubles.
Changing the oil and filters isn't going to fix an acceleration issue. Start with fixing that first. Plugs are the logical first step but here are a couple other ideas. Is the supercharger working, belt tight, feel the boost? I believe yours has a clutch that engages at 2500. Can you tell if that's engaging?

I'm also a bit confused by your post (paragraphs are helpful). Is the cel on? If so obviously pull the codes and post them here.
I would also reset the throttle, that should help your issue along with cleaning the MAF.
Changing the oil and filters isn't going to fix an acceleration issue. Start with fixing that first. Plugs are the logical first step but here are a couple other ideas. Is the supercharger working, belt tight, feel the boost? I believe yours has a clutch that engages at 2500. Can you tell if that's engaging?

I'm also a bit confused by your post (paragraphs are helpful). Is the cel on? If so obviously pull the codes and post them here.
This is from his first post.

First off I am showing no CEL but the light does come on when I start the car so I'm pretty sure it's not the bulb.
Hoping for the best

Thanks for the encouragement guys. Just to clarify a few things I am changing the plugs and wires as part of the service. I will also be doing the full check and repair of the most common issues I found on the search. MAF cleaning, K40 check and solder, Vacuum leak check, Fuel rail pressure check, and I will be resetting the throttle. As I said in my original post there is no CEL on but the bulb is good. Once again thanks for the suggestion is there anything else that I should check while I have it in the shop???..........CHEERS:grin:
This is from his first post.
I did see that and was looking for clarification as 'I'm pretty sure it's not the bulb' didn't make sense. To the O/P, was the car running like that when you bought it? What did the p/o say?
Update Throttle hesitation

Hello...well we got a big dump of snow this weekend so i didn't take the car into my shop, but i did do some of the stuff in the garage at home. I changed the air filter it was filthy, i changed the cabin air filter (filthy), and i changed the plugs. checked the vacuum lines and check all the engine plugs for good contact and did the throttle reset as per the instruction i found on here. Couldn't change the fuel filter or engine oil and filter, no ramps or jack stands to get under it.
I did reach under and pull part of the fuel filter cover off to have a peek at the fuel filter and it looks original, i gave it a few shakes to see if it might free up some sediment if plugging was my issue.

Then i took the car for a little drive and now it seems to have a better response on the initial applying of the throttle no more hesitation on a full application and the 0-60 improved to about 9.5 sec, but...now and this is what i think killed my 0-60 time. When i hit about 3200 RPMs it tops out won't go past it just seems to flatten right out. It doesn't sputter or die off it just hits that rpm and won't go past it. In hind sight i think maybe shaking the fuel filter may have done worse for it. It seems like it just won't get any more fuel at that RPM. I did get it to go past that RPM after the test run i was driving back home and was manually shifting and as i came around this turn i gave it a little extra throttle and it felt like the boost just kicked in and it took off like a rocket. but then back on the straight it topped out again. NOTE** i did check the Supercharger several times and the clutch pulley kicks in right around 2300 RPMs every time**

Back to the CEL now it does not come on when i start the car and could have sworn it came on before when i started it. That's why i was sure it wasn't the bulb but now i am thinking the bulb may be done in. Does anyone know if there is a fuse that is connected to the CEL that i may have pushed or bumped when i was check the electrical connections? All the rest of the dash lights work.

Hopefully we are done with the snow and i can get it in the shop this weekend to finish it up. Any advice on my new results would be appreciated.

CHEERS
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Does anyone know how i can check if the CEL light is working? I have read that if the fuel cap is not securely fastened on it will cause the CEL to come on is this true and is there any other way i can check if the light works?

CHEERS
If it does not come on when you first turn the key to on, then your bulb is bad.
Update bad Throttle Hesitation

Hello Fellow SLKers


Well I got the car in the shop last weekend and I got the problem sorted out. I did the fuel filter and tested the car**no change in the problem**. Checked the K40 Board and it was all good **no change in the problem**. Hooked up a vacuum gauge **all good no change in the problem**. Checked the fuel rail pressure ** 54PSI all good**. So I pulled of the MAF cleaned it completely and reinstalled it **SUCCESS**. For some reason just pulling the plug to test it made no difference, but to pull it off and give it a good cleaning made all the difference.
I Took it for a 0-60 run and I pulled just under 7sec no hesitation, no flat top, no sputter it runs like a charm now...Yahhhh
I still can't check for any codes because I don't have my 28 pin cable adapter yet. But I think I am all good now with the exception of a couple of small issues to sort out. So thanks everyone for your input and I will be starting a new thread for my other issue....CHEERS:grin:
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That's great! run the gas down and throw in some Techron or similar in your neck of the woods

http://www.slkworld.com/general-dis...ock-sluggishness-hesitation-top-tier-gas.html
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