Hi, 2000 CL500, parked before winter in a garage. Changed all the plugs last year with Bosch Platinums, and it ran great for the summer and when parked. Was a long winter, and it didn't come out until June this year. I did forget to put in fuel stabilizer, and with the 7 months it sat for I assumed perhaps its the issue. Even know all my other summer equipment is all running fine. It had 3/4 of a tank in it, which I topped up added some treatment and octane booster too and drove it on the highway to get rid of the old gas. It ran really rough, and goes into limp mode sometimes. I got it down to the reserve mark (1/8th tank) and put in two more fuel cleaners (royal purple, stp the first time) and filled it with fresh premium. It is now down to half a tank and still running the same way. I feel it should be atleast "better" by now but it is still terrible. There was alot! of snow last winter and the garage got a lot of water in it, there was a fair bit of white corrosion over the engine. I just finished pulling all the plugs, checked the gaps, cleaned the back ground connections for all the coil packs and no difference. The plugs have a lil bit of oil only at the top threads, are a nice brown/tan color, but the front cylinders were wet, a taste test told me nothing. I assume just unburned fuel.

The codes are currently misifre cyl 1, cyl 5, random misfire. (The fronts)

The codes while driving before varied from misifre cyl 1, cyl 2, cyl 5, cyl 6, random misfire.

Again prior to parking it, it ran fine. It is gutless now, making very little power, and shaking at idle. However for the first couple seconds upon starting it seems to run smoother.

I need to get the fuel pressure tested yet, and change the fuel filter. But I'm basically guessing now, and don't want to buy a new fuel pump without evidence. Also it does fire right up, (starts with no hesitation whatsoever).

Has anyone experienced anything like this before? I'm starting to scratch my head on this one.

 

Read codes and report back.

Compression and leakdown.

Bubbles in coolant tank?

Milk shake brown sludge under oil fill cap?

Steam coming from tailpipes?

Rough idle?

Pics of each plug?

Coil replacement is regular maintenance in my book, especially with an old car like this one.

 

Bought a new Fuel Filter and Fuel Pump, I am not changing the pump out yet as the Fuel Filter seems to be putting black fuel to the motor (filter port). I'll be sure to post my final results yet..

 

A slight improvement made after the new filter. Slightly, still missing on the front 4 cylinders. Its very odd how its only the front 4. I got my old "AutopTap" scan tool out and recorded a couple runs with it. One of the 02 sensors looks a bit funny, same with that one Long Term Fuel Trim. May have to inspect the 02 sensors yet, but it would be very odd that they all of a sudden went bad after a winter storage..

 

So I pulled all the spark plugs which are less than a year old, checked gap etc, the entire fuel rail and all the injectors, bench tested them and cleaned them, all working properly. I checked the coils for spark, and it has a brand new fuel filter and fuel pump.

There must be a fuel regulator somewhere in this car, but can't find it, is it buried under the car within all the covers, anyone know?

Thanks

 

Throw parts at this old car.

Everything electrical: plugs, coils, O2 sensors, crank position sensor, cam position sensors if present, coolant temp sensor, battery(ies).

Swap injectors from good 4 cylinders to bad 4 cylinders.

 

It fires up fine, and runs fine for 5sec, then starts missing.
Tried some new plugs again, and a different battery no difference.

 

New parts from the dealer. You have an electrical problem, it needs to be solved with new electrical parts from the MB dealer. OEM battery, plugs and coils would be first on my list. Then start replacing sensors.

Does this engine family have a reputation for intake manifold flaps breaking, or timing chain or cam adjuster failures?

This engine has two spark plugs per cylinder, correct? More reason to focus on battery-coils-plugs.

 

I know that on my engine, the cam adjuster failure is quite common, read, I'm probably facing is myself.

I recommend that you read in on the function documents that WIS has to offer (they start with GF, GF07.61-P-4021L for example), so that you understand what the ECU and all the other ECU controlled features are doing.

That really helps you to understand what does what and allows you to exclude certain parameters from your diagnosis