andy_breuer

Hey there, I’m sorting an annoying issue with my 2003 CLK430 and having difficultly resolving. Advice needed.

96,000 miles
CEL light comes on 3-5 driving cycles after throttle reset procedure.
The freeze frame data indicates the CEL happens at idle conditions when warm.
P0171 code and sometimes P0174
left and right bank lean

What I have done so far:
1. replaced fuel filter
2. validated fuel pressure 55psi and stable
3. replaced throttle position sensor
4. Replaced map sensor
5. replaced 4 vacuum hoses
6. validated idle vacuum is 15.5inHG
7. validated gap on spark plugs
8. replaced mass air flow sensor
9. validated intake runner flaps operating properly
10. used Techron fuel system cleaner
11. validated that all fuel injectors cycling

All of these items were relatively inexpensive and easy to replace with Mercedes parts and would recommend these updates to anyone else. I have noted significant overall performance improvements with the car including improved performance. But I am still seeing the CEL and what seems like a 25-50% power reduction from 1000-3000rpm after 3-5 driving cycles from fresh TPS reset.

What should I try next?

A. Crankshaft Position Sensor
B. Camshaft Position Sensor





Thanks,
Andy

andy_breuer

Update:: I replaced both camshaft and crankshaft position sensors and no major improvement. Then I validated the EGR was working properly.

Final solution: fuel injector replacement, but it was likely just the seal on cylinder number five, see the debris in the port of the attached photo. Directly after replacement the short term fuel trims had major -25% adjustment to reacting for the lean condition correction.



And the oxygen sensor rich condition at startup as shown in the graph that reverted to proper operation.

andy_breuer

And the seat of the pants feel is there, too. I’m gonna need those rear tires a bit sooner now😂

austinramsay

Nice! Thanks for posting your solution!

ToplesSadie2003

Nice, I'm down to those two options as well on another car. Camshaft sensor or Fuel Injectors, I guess could be a ground too maybe… cyl# 1 misfire

andy_breuer

Well, the saga has continued. CEL has come back on, so I have continued repairs.

The latest replacement is the intake manifold gaskets and knock sensors. Have noted significant improvement in idle, and all clearance of codes.



note the before and after smoothing of ignition advance at idle (when the CEL was happening). I believe the knock sensors were the root cause, but not sure as I completed both services at once.

andy_breuer

In this time I also replaced the engine mounts and have noted a huge improvement in smoothness and drivability.

New on left, and old is 1/4” shorter and collapsed. I also replace transmission mount at the same time. Well worth the money and effort. ($200 total and about 1-1/2hr to change each)