My car has been basically undriveable for about 3 weeks so any help is GREATLY appreciated. Before these issues started I never had any problems with my car. It's a 2004 C320 4Matic.

On a really warm day my wife took the car out and it threw a P0335 code and would not restart for about 20 minutes until the car cooled down. It had all the indications of a bad Crankshaft Position Sensor. The shop reset the MIL and I went on my way thinking it wasn't a big deal, I would just replace it when I had time.

A few days later I'm merging on to the freeway (high in RPM range) and it throws another P0335 code and shuts down my engine. I pull on the shoulder of the freeway with no steering and the car immediately restarts. So I limped home and we had the dealer replace the CPS.

Three days later I'm driving down the freeway and I have a P0400 (EGR Malfunction). The car didn't die, but I went to a shop and had the code read and they said it would be fine until I got the EGR fixed. Later that day, I'm accelerating from a stoplight and get another P0400 and a P0171 (System too Lean). The car died that time.

I had an independent MB shop replace the EGR valve and clean the tube that goes to the intake. It was clogged with carbon.

The car has also during this whole time has been lagging from stops and stumbling (but not dying yet) when coming to a complete stop.

Yesterday I'm driving home and accelerate from a stoplight (probably hit 4k rpms as I wanted to "see" if it would break in higher rpms again -- it did) and the car registered a P0335 again. CPS issue. Since it was just replaced, I'm thinking this is not the issue but a symptom. Car again restarted fine.

Today, I took it out to see if I could duplicate the issue and the car is stalling/stumbling while coming to a stop and at one point died at a stop sign with a "Battery/Alternator. Visit Workshop" error. No codes. It again immediately restarted. I then went up a driveway with a large incline and had some misfiring and no power for about 4 or 5 seconds. I thought I was going to stall or roll into the person behind me, but it eventually "caught" and I made it up.

Anyone have any idea what could be the root symptom for these issues? I've spent almost $1000 so far trying to fix this issue with no success at all. I would rather not take it to the dealer again and spend hundreds more dollars if they're not going to fix it.

 

Had the same problem with mine any time I went over 4k rpm. Idled very rough and then stalled the moment I hit the gas. Mine didn't throw any codes, though. Took it to my indy who I believe said that it was moisture buildup that was related to the CPS . It looks like it was an early sign of a going CPS. I got it "fixed" (not replaced) about 2 weeks ago, and I've had no problems since.

 

Fuel, spark, spark at the right time, air are required.

Check.

CPS (crankshaft position sensor)
Coil packs & plug wires,
Air filter & that airbox is clipped down tightly over the MAF
Fuel pressure at the front rail Schrader valve should be 3.8 bar or 55 psi while cranking.
Fuel filter
Start enable fuses 31, 52 & 57

Also check all vacuum lines.
O2 sensors cycling too slowly can cause stumble but I would expect a code.

Good luck!

 

Thanks for the response Bill and Glyn.

Two questions:

1. Since the CPS was replaced and it still threw a P0335 code... Could the replacement CPS be bad? Or a problem with the circuit/computer? Or can something unrelated cause a P0335?

2. "Air filter & that airbox is clipped down tightly over the MAF"

This was a concern of mine because the ring that anchors the MAF to the intake is loose. It seems like it's either broken or was not installed correctly. What would be the symptoms if the airbox is not sealing with the MAF?

 

New CPS could be bad or poor connection somewhere.

If the airbox does not seal on the MAF it causes the MAF to hunt with all the symptoms you have. It can also cause spurious codes.

 

I had to replace the MAF and a couple of vacuum lines

 

Your CPS was replaced with new OEM Mercedes CPS right? Some of the aftermarket CPS are crap,... comes with corrosion!

Use some Techron to clean carbon buildup.

Issues tend to happen from acceleration mode,... so I'd look at fuel pressure,... is it low? If so why,... faulty fuel pump or clogged fuel lines/filter,.... Do you use ethanol gas? What is mileage?

 

Thanks for all the help guys.

Glyn was spot on with the diagnosis. I went out on the 20th and fixed the bracket that holds the MAF to the intake. It wasn't broken, they just didn't install it properly. I "clicked" it in place and made sure the air box seated down properly.

Since then I have driven it probably 30 times with no issues at all! No more surging idles, no more dying at stop signs.

Thanks again Glyn.

 

Pleased it's sorted!

 

Oops