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2001 clk 430 cabriolet
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Discussion Starter · #1 ·
I have a 2001 CLK 430 with 142000 miles, when I bought it 14 months ago it had 130000 miles I replaced sparkplugs Bosch iridium fine wires, air filters (with K&N), O2 sensors, fuel filter, oil/filter etc. About 5 months after I bought it I started to experience hesitation and stumbling if I accelerated past 3500 rpm and more than 75% throttle. I scanned car and P300 and misfire codes for all cylinders were present. I replaced the MAF sensor reset computer. The problem still occurred but it became very sparse and random but still the only codes were random and cylinder misfire. Currently the issue is worse the car will have the codes as soon as the engine speed is above 3000 rpm in park or neutral or while driving if car is given more than 50% throttle or engine speed gets close to 3000 rpm. I check the spark plug wires resistance, the wires are marked 2K ohms and I showed 2.1K-2.7K ohms. The spark plugs are all showing signs of center electrode wear and carbon deposits on the insulator. Can anyone give me some guidance as to what steps I should take next? I need this car to commute to work and need to fix the problems A.S.A.P.
 

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Discussion Starter · #3 ·
@ W208 Hawkwind, its a Bosch part I still have the original MB part in garage. After searching through all the threads on this type of issue I'm thinking off doing a hail mary play. I just pulled all of the Bosch iridium plugs after 10k miles the center electrodes are destroyed so I return them to get my $112.00 back. I ordered new wires, cam and crank sensors, new platinum plugs, new breather hoses, intake gaskets ( I am going to remove and inspect clean if necessary), new valve cover gaskets to finally fix my oil leak, and motor mounts I noticed that the left mount is damaged. So hopefully the combination of items I am replacing will fix this problem for good if not I don't know what I will do, probably sell it or part it out. I am just stumped. :confused:
 

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1999 W208 CLK320
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@ W208 Hawkwind, its a Bosch part I still have the original MB part in garage. After searching through all the threads on this type of issue I'm thinking off doing a hail mary play. I just pulled all of the Bosch iridium plugs after 10k miles the center electrodes are destroyed so I return them to get my $112.00 back. I ordered new wires, cam and crank sensors, new platinum plugs, new breather hoses, intake gaskets ( I am going to remove and inspect clean if necessary), new valve cover gaskets to finally fix my oil leak, and motor mounts I noticed that the left mount is damaged. So hopefully the combination of items I am replacing will fix this problem for good if not I don't know what I will do, probably sell it or part it out. I am just stumped. :confused:
I would change one thing at a time, starting with the plugs and then test.

If you change half a dozen things and it solves the problem that's great, but you'll never know what the problem actually was. Might save you a heap of cash.
 

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Discussion Starter · #6 ·
I have never heard of such degradation to Bosch sparkplugs in only 10k miles. Are you convinced that they are not Chinese knock-offs?

@keyhole I would hope they were actual Bosch sparkplugs I purchased them from my local Advance Auto Parts store and shockingly they had the Iridium fine wires in stock and not the platinum. I plan on getting NGK or autolites never had a problem in the past and this was my first time ever using Bosch plugs and my last.
 

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Discussion Starter · #7 ·
I would change one thing at a time, starting with the plugs and then test.

If you change half a dozen things and it solves the problem that's great, but you'll never know what the problem actually was. Might save you a heap of cash.
I was planning on doing the valve cover gaskets anyway to fix my oil leak, I tested all of the sparkplug wires and all measured higher than the 2K Ohm factory rating. Lowest reading was 2.2K ohms and highest was 3.8K ohms. so I figure I will start with plugs and wires then determine a game plan if the issue still persists.
 

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Have you checked the coils?
Why are you burning your iridium plugs? Are the plugs too hot? Anything wrong with the engine? Compression?
Are you sure the central electrodes are destroyed? Can it be dirt around the electrodes?
I've been using NGK iridium (different engine). I bought a new set to replace the old plugs (80.000 miles) and couldn't tell the difference from the new ones (ok, I'm using LPG. For sure it's not the same. But on my bike, on gas, I also use NGK iridium and they just don't get old).
Also, the impedance you measure on your cables and coils is on low voltage. The measurements could turn right and still you would have leaks with high voltage.
 

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2001 CLK320 Cabrio
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The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring.

Possible causes:

Faulty spark plug (s)
Faulty ignition coil (s)
Clogged or faulty fuel injector (s)
Intake air leak
Fuel injectors harness is open or shorted and/or poor electrical connection
Ignition coils harness is open or shorted and/or poor electrical connection
Insufficient cylinders compression Incorrect fuel pressure

Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring.

If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see other "Possible Causes" above.

I'm not a huge fan of changing lots parts, hoping the problem goes away.

I'm not a huge fan of buying parts based on marketing hype.

I'm a huge fan of only using parts that MB specified in their design. The OE parts come in a box with the MB logo. However, MB usually doesn't manufacture these parts and you can save a ton of money by buying OEM parts, (e.g. same part but comes in a box without the MB logo).

I recently changed by factory plugs, at 95,000 miles and 16 years later, although the factory installed Platinum plugs were running fine and when removed, showed little wear. It was a real PITA, but thankfully the CLK320 only has 12 plugs. Had to remove the top of the air box, MAF and bellows. Reinstalling the bellows onto the intake tube was another PITA (e.g. it's a snap fit that wasn't obvious and takes a lot of force to refit). Also, each cylinder was 2 plugs, so make sure the wires are reattached in the right order (e.g. the valve cover and boots are marked to make sure).
 

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Discussion Starter · #10 ·
The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring.

Possible causes:

Faulty spark plug (s)
Faulty ignition coil (s)
Clogged or faulty fuel injector (s)
Intake air leak
Fuel injectors harness is open or shorted and/or poor electrical connection
Ignition coils harness is open or shorted and/or poor electrical connection
Insufficient cylinders compression Incorrect fuel pressure

Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring.

If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see other "Possible Causes" above.

I'm not a huge fan of changing lots parts, hoping the problem goes away.

I'm not a huge fan of buying parts based on marketing hype.

I'm a huge fan of only using parts that MB specified in their design. The OE parts come in a box with the MB logo. However, MB usually doesn't manufacture these parts and you can save a ton of money by buying OEM parts, (e.g. same part but comes in a box without the MB logo).

I recently changed by factory plugs, at 95,000 miles and 16 years later, although the factory installed Platinum plugs were running fine and when removed, showed little wear. It was a real PITA, but thankfully the CLK320 only has 12 plugs. Had to remove the top of the air box, MAF and bellows. Reinstalling the bellows onto the intake tube was another PITA (e.g. it's a snap fit that wasn't obvious and takes a lot of force to refit). Also, each cylinder was 2 plugs, so make sure the wires are reattached in the right order (e.g. the valve cover and boots are marked to make sure).
My first steps will be to change plugs and wires, replace valve cover gaskets, verify fuel pressure electrical connections and coil operation and do a spray test again for vacuum leaks.
unfortunately the previous owners seem to have been very lax on vehicle maintenance and had local mechanics do most of their work which was evident when I looked at the fuel filter which the mechanic "replaced" on an invoice yet it had a Mercedes date code which corresponded with the cars factory build date I found the same issue with the O2 sensors and the original sparkplugs that I replaced just over 10k miles ago. so I have the difficult task of trying to determine what if anything was ever properly maintained or replaced.
 

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I would do a few simple things...all revolving around MAF...If you search this issue on both threads, these codes invariably end up at the MAF.
I would change the MAF with an OEM from autohauosaz.
Check that there are no leaks in the vacuum lines
be sure to seat the air filter cover correctly....seat the back firmly on MAF, hold that down and gently lower front into clips.

Please report back.
 

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Discussion Starter · #12 ·
@tomtomtomtom Ok so I tore into the engine and found several highly disturbing things; both engine mounts and transmission mount had completed disintegrated, the vacuum lines from the valve covers not only hard as steel but had cracks on underside of tubing, MAF sensor elbow gaskets hard as a rock and sealing to manifold and MAF non-existent, fuel injector O-rings hard as rock injectors moved freely in manifold, trying to remove factory spark plug wires resulted in wires leaving terminals in coils, 3 factory ignition coils packs, had signs of swelling and heavy corrosion of mounting area, engine ground strap to frame completely ripped apart (from lack of engine mounts). I have since replaced engine and transmission mounts, ground strap, all injector O-rings and inlet filters, new coil packs, new sparkplug wires, new valve cover gaskets, all vacuum lines from valve covers to manifold and MAF elbow, I attempted a sealing repair on the elbow gaskets using a non-hardening gasket silicone. I will attempt to reset the ECU and road test it this afternoon after the RTV for the valve cover breather/fill cap covers has fully cured. Hopefully this has fixed the issue or I guess I have a vehicle going up for sale with after market rims and the factory AMG's included.
 

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Discussion Starter · #14 ·
@tomtomtomtom ok so took out for road test this afternoon for about 7 miles. no oil leak anymore & ride is 100% better with new mounts. went over 3000 rpm no random misfire codes engine runs smoothly. pulled into driveway and CEL lit up plugged in my equus scanner saw codes for o2 sensors bank 1 sensor 2, bank 1 sensor 2 heater, bank 2 sensor 1.
 

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doubt that it is o2 sensor....do searches on both mb forums, you will see this come up over and over for years...they invariably turn out to be bad MAF sensors or vacuum leaks that cause these codes to be thrown. If you are sure that the vacuum lines are good...order an OEM MAF from a reputable US distilled... ex autohausaz.com
great that the ride is better!
 

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Discussion Starter · #16 ·
l did my normal commute with car today and only had P0141 and P0136 come up and CEL lit up when I shut off car for 5 minutes to wait for my wife to walk out of work this AFTERNOON. Car is averaging over 21 mpg according to dash, no hesitation, shaking, poor performance I included freeze frame from this afternoon. for codes any thoughts?
 

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Discussion Starter · #19 ·
at this point I will probably leave it be, the car is due for inspection in December I will do the MAF and O2 or just let it fail I will get a list from NJ DMV inspection of items to replace to attempt re-inspection I will worry about it then.
 

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From what you've found, it seems the car has been pretty neglected.

New engine and gearbox mounts transform the way the car drives and idles.

Glad you've made some progress, sounds to me as though you're almost there :wink

It's amazing how much neglect these cars can take.
 
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