I picked up a 2002 CLK430 Cab. about a year ago. Ran pretty nice when I bought it but needed some maintenance things (Oil, Air Filters, Spark Plugs, Valve Cover Gaskets). Ran great for a while until I noticed the CEL come on for P0171, P0174, and P0104. Lean A/F mixture on both banks and Intermittent Mass airflow circuit. Replaced the MAF to no effect. It progressively got worse to the point where the car would stall at idle or intermittently try to die, or catch itself by revving. I then replaced an ignition coil (Cylinder #4) for a P0304 Code that occurred, and all 16 spark plug wires while I was at it. Misfire was fixed but car ran horribly like it was losing a lot of vacuum, and had to fight to even stay alive. I then took it upon myself to do a lot of work replacing vacuum lines, breather hoses, injector seals, cleaning the Throttle Actuator, and splitting open the Intake Manifold for cleaning (inside was caked in black carbon.) After reassembling everything, the car starts, idles low and very rough, Revs itself to ~3000RPM, and dies right after. If I give the car a tiny bit of stable gas, it can stay alive at ~1000RPM running really rough with some intermittent popping sound(throttle body? intake runners?). After a couple times of the car doing the rev-itself and die right after, upon starting the engine it will just give up and stall right after your turn it on. I’ve attached two videos detailing both scenarios. Exclaimer: I have the air cleaner and plastic intake bits off of the car in the videos so my friend (recording) can see if the engine is shaking, leaking anything, and can tell where sound is coming from. Symptoms remain the same with Plastic intake installed.

Any help is appreciated. I’m really lost and don’t want to throw more money at parts that won’t fix it. Thanks.

 

Thanks for the videos, that is helpful. So - my thoughts are that this issue is happening in Open Loop control at startup, so most sensors (O2, knock, maybe MAP, coolant temp) should not be in control yet. If you’re getting lean code at this point you should probably start checking Fuel Filter and or Fuel Pump as the culprit. You can get a fuel pressure gauge for less than $20 and attach it to the black knob on the fuel rail on the front of the engine. With the key on and engine off, the pressure should read 50psi, then if you get the motor running, it should still read that level.

What is your fuel pressure at the engine?

 

Good thinking. I will scan the codes as I must have been too clouded by confusion to remember to scan the codes, but in the small amount of time that the car would stay on I don’t think the ECU had enough time to throw a code, but will look regardless.I Also will check my fuel pressure at rail as I have seen recommended to other people with similar problems to mine. Thanks man, Appreciate your help!

 

Okay Andy, I rented a Fuel Pressure Test kit to attach to the fuel rail shrader valve like you suggested, and got a reading of 50psi at the rail with the engine off and key in the ON position, and ~53psi with the engine running. There are no codes in the ECU, but I did have to get a new battery for this car and I don’t think the engine stays running long enough to present any codes, even though it had P0171 and P0174(lean codes) a while ago. With my fuel pressure reading, does that rule out fuel pump and fuel filter? Or maybe try to replace at least the fuel filter anyway due to age(22 yr old car, probably original part)? I also took a vacuum reading using one of the PCV breather hoses and the needle bounced between 4-7 in. Hg. Since I had the intake manifold cleaned (and thus removed) like I mentioned, do you think I’m leaking vacuum from the manifold gaskets? I have rechecked and replaced all the vacuum hoses going to the manifold so I’m pretty positive it isn’t those.

 

A vacuum gauge should measure over 15 inHG and/or the OBDII should be reading 10-11inHG at idle. It sounds like you might have a vacuum leak. Try attaching a rubber glove and straw into the MAF like the attached photo, and if you stop blowing into it the fingers should stay inflated for at least 1-2 seconds.

 

Check the fuel pressure, seems like a weak fuel pump.

 

Is the boot cracked below the MAF? A sit in the rubber boot can also throw these codes, or if it's not seated right to the throttle body. Sorry to hear you're dealing with this. Good luck to you. Also check the rest of the forums since the M113 engine was commonly used across the S, E, SL, and ML classes.

 

Long time no revisit. I apologize, life and school got in the way. Recently, however, I found a junkyard ‘99 CLK430 and picked up a used intake manifold that hasn’t been tampered with like mine has(I think I mentioned this earlier, but I split my manifold to clean it). So this was just going to be a test. After installing the used junkyard manifold, I re-took-apart the manifold that came with my car to find that the plastic linkage that holds the arm that moves the runner flaps had somehow broken off?? Totally explains the horrible condition this car ran in, flaps were literally inoperable by the little outside air valve. Regardless, started the car with the new manifold and it actually was able to start and stay alive on its own, and drive under its own power. However it was obviously missing pretty bad, and making a pretty loud hissing noise(vacuum leak?) After a drive to warm the engine/computer up, I had codes for misfires on cylinder #3, #5, and #6. I wonder if this has something to do with the injectors (had to take off fuel rail to remove manifold, and refit the seals), or the gas that has been sitting in the car for a couple months, or wiring connectors not making good contact with injectors/coil packs. Not sure how to really find out either. I can’t take a look at the car until this weekend since I started school and it’s still at home, so If anyone could provide me a direction to look in that would be a tremendous help.

 

i would spend the time going through the vacuum system, if the car is hissing, you have a vacuum problem

 

Thanks for coming back and keeping us updated. It seems that whatever steps you took to disassemble and clean the car ended up having an effect opposite to what you intended. I find it intriguing when people in the community talk about the drawbacks of using additives and other products for car maintenance. I'm planning to do a transmission flush on my car soon, but one thing I won't be doing is cleaning the engine and transmission with chemicals.