Weird stutter when hot
Thread Starter
Newbie
Joined: Apr 2024
Posts: 7
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2002 CLK 430, 2007 C230
Weird stutter when hot
I've seen a few people with this issue over the forum, but cannot for the life of me find any resolution.
I have a 02' CLK 430, coming up on 83k miles. When the car in in gear, idling on a hot day, the engine will sometimes drop RPMs like it wants to shut off, then rebound as if nothing happened. Then occasionally if sitting again in traffic if I attempt to accelerate, there will be a stutter that feels like the car wants to shut off very briefly, then kicks off like nothing is wrong. This will occur once a blue moon, and has no rhyme or reason when it occurs other than during hot days (I can sit idle in traffic all day long during colder months, and it will never happen). It is very unreplaceable, and despite my best attempts, I can literally never get it to occur when I'm trying to diagnose the issue.
I have no check engine light, and the car normally runs like silk save for this occurrence in hot weather while idling. The car has never even came close to overheating either, so cooling is not an issue as far as I can tell.
Things I have done:
Regular Oil Changes
Replaced Mass Air Flow Filter
Replace Sparks
Replaced Air Filter
I've seen the CPS and Throttle Body come up a few times, but people have ranged from saying that's not it, to "just hook it up to a star computer." Any advice will be appreciated.
I have a 02' CLK 430, coming up on 83k miles. When the car in in gear, idling on a hot day, the engine will sometimes drop RPMs like it wants to shut off, then rebound as if nothing happened. Then occasionally if sitting again in traffic if I attempt to accelerate, there will be a stutter that feels like the car wants to shut off very briefly, then kicks off like nothing is wrong. This will occur once a blue moon, and has no rhyme or reason when it occurs other than during hot days (I can sit idle in traffic all day long during colder months, and it will never happen). It is very unreplaceable, and despite my best attempts, I can literally never get it to occur when I'm trying to diagnose the issue.
I have no check engine light, and the car normally runs like silk save for this occurrence in hot weather while idling. The car has never even came close to overheating either, so cooling is not an issue as far as I can tell.
Things I have done:
Regular Oil Changes
Replaced Mass Air Flow Filter
Replace Sparks
Replaced Air Filter
I've seen the CPS and Throttle Body come up a few times, but people have ranged from saying that's not it, to "just hook it up to a star computer." Any advice will be appreciated.
Super Member
Joined: Apr 2007
Posts: 737
Likes: 38
From: Fort Worth, TX
2019 CLS450/ 2002 CLK55
Mass air flow filter? You mean you change the screen in the front of the Mass air flow sensor or the intake filters for the engine? Or did you change the mass air flow sensor entirely? Did you use an OE Bosch unit? The knock offs tend to fail.
Could be a crankshaft position sensor starting to go, fuel filter, or maybe even a vacuum leak?
I'd clean the MAF sensor and throttle body, change the fuel filter (if you haven't), and check for leaks.
John
Could be a crankshaft position sensor starting to go, fuel filter, or maybe even a vacuum leak?
I'd clean the MAF sensor and throttle body, change the fuel filter (if you haven't), and check for leaks.
John
Thread Starter
Newbie
Joined: Apr 2024
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2002 CLK 430, 2007 C230
Member
Joined: Jun 2024
Posts: 118
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From: Midwest
CLK 430
I’ve got a CLK 430 and had a similar issue, and have been able to resolve it. Mine would stumble more regularly and eventually the check engine light would come on with a “lean on bank 1” error. The stumbling was actually the timing getting retarded, due to a perceived timing knock. I was able to resolve by replacing the knock sensors and intake manifold gaskets. The service takes 2-3 hours and about $40 in parts. Your light doesn’t come on likely because it isn’t happening often enough to trigger, but will likely in the future if this is the issue.
Thread Starter
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2002 CLK 430, 2007 C230
Trending Topics
Super Member
Joined: Apr 2007
Posts: 737
Likes: 38
From: Fort Worth, TX
2019 CLS450/ 2002 CLK55
When you change the fuel filter make sure you get the Mahle filter. I used a no name autozone brand and it caused howl at the hose from the pump to the filter. Yes, you read it right. Several others have had similar issues, so make sure you get the Mahle.
https://www.autohausaz.com/pn/002477...YaApD9EALw_wcB
John
https://www.autohausaz.com/pn/002477...YaApD9EALw_wcB
John
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Thread Starter
Newbie
Joined: Apr 2024
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2002 CLK 430, 2007 C230
So I hate to necropost but did want to say I finally figured out the problem. Changed out literally everything that seemed could be an issue, new filter, changed MAF, plugs etc.
It was the accelerator position sensor going bad combined with a failing TPS that just hadn't given up the ghost yet. Anyone who encounters this problem is advise checking your accelerator position sensor as your car will not throw a code for it more than likely, but it may leave a pending code as what it finally did with mines.
It was the accelerator position sensor going bad combined with a failing TPS that just hadn't given up the ghost yet. Anyone who encounters this problem is advise checking your accelerator position sensor as your car will not throw a code for it more than likely, but it may leave a pending code as what it finally did with mines.
