My wife has a 2006 E320 CDI that she has driven since new. It now has 156,000 miles on it. It has been a very reliable car and she likes it a lot, but lately it has been acting up, and I am hoping someone on the forum will recognize the symptoms so we can get it properly fixed.

It all started when she got in an accident with it. She bashed in the front at a slow enough speed that the air bags didn’t go off, but fast enough to require about $10,000 in repairs. With 156,000 miles, I thought the insurance company would have totaled it out, but they didn’t, and we have had problems with it since getting it back from the body shop. It’s only been driven about 300 miles since the accident.

It now frequently goes into a mode where it produces very little power. As those of you with 320 CDI’s know, the car normally has plenty of power, but when it goes into this low-power mode, it will not exceed 3000 RPM, the transmission will not kick down properly, and if left to its own devices it’s hard to get it over about 50 mph. You have to manually shift it to get it going, and even then it feels very sluggish.

We took it to the dealer (who has maintained it since new), and they replaced the EGR valve, updated the CDI control unit, and replaced the actuator motor for the intake shutoff. They also replaced the thermostat (which must have been damaged in the accident, since before replacing it, the water temperature wouldn’t get above 60 degrees), charging me a total of $2100. That made no difference, except that now it turns on the “check engine” light which it did not do before.

When my wife took it back to the dealer to get them to try again, they reported the following:

“We found excessive carbon buildup throughout entire engine causing intake manifold flaps to bind and not fully open and therefore there is not enough air travelling to the cylinders to fire. In addition to that the EGR system is also clogged with carbon causing exhaust fumes to build back pressure to motor”.

And suggested that we give up on the car. They didn't tell me what code was causing the check engine light, and I am too irritated with them to communicate further with them.

I think the dealer simply doesn’t know what is wrong and is hoping we’ll just buy a new car, accepting their low-ball trade-in value. Here are some observations:

1. When it goes into low-power mode, if you turn the car off and turn it back on, it runs with normal power for a while.

2. When it is in the low power mode, even if you put it in neutral and push the accelerator, the engine will not exceed 3000 RPM. When it is running normally, it shoots up above 4000 RPM quickly and easily.

3. If you drive the car aggressively it doesn’t go into the low-power mode. I took it out on a local highway for an “Italian tune-up” and drove it in third gear at about 80 mph for 20 miles or so and there was no sign of problems until I got off the highway and drove on surface streets for a while. Then it went into limp mode until I turned if off and on again, whereupon it ran fine (driving normally) for 10 minutes or so before again going into limp mode.

4. When it came back from the body shop, the alternator wasn’t working correctly even after replacing it with a new one. The dealer was able to diagnose this as a pinched wire in the wiring harness, and they did fix it (which I was impressed with).

If the dealer’s diagnosis was right, the car would run poorly all the time, rather than going into and out of the low-power mode. It acts like there is some sort of sensor that is intermittently giving wrong information to the engine control unit, causing it to limit fuel or turbocharge boost or something. The fact that there was accident damage to the wiring harness to the alternator might mean that there was other damage as well. It seems nearly certain to me that the problem was caused by the accident somehow.

The diesel models are pretty rare around here, so I don't know of any shop that specializes in them. I'm going to take it to an independent shop that specializes in German cars in general and works on some Volkswagen CDI's, hopefully they'll be able to fix it. But if you have any educated guesses as to what could cause the symptoms described, please feel free to share them.

Thanks in advance for any suggestions or advice.

Barry

 

I just had my 2007 in for the build up in the intake manifold which caused my CEL to come on and I had no turbo. I bought the car with 35,000 miles on it in 2010 and have been very happy with it until this issue at 77,000 miles of freeway driving (I commute 120 miles daily). I have the car maintained at all the scheduled intervals and this manifold problem cost me $2,356.00 to fix. I hope this doesn't happen again but that is at least what you will need to spen to get our car running properly.

 

Jigsaw,

Did you have the same symptoms of the car running poorly and then running correctly if you turned it off and restarted it?

Thanks,

Barry

 

"And suggested that we give up on the car. They didn't tell me what code was causing the check engine light, and I am too irritated with them to communicate further with them."

After spending the amount of money you have at the dealer, giving you the "code" should be part of your overall service. The error code could be your starting point as to what is causing the problem. Most auto supply stores will be happy to use a code reader, and give you the results. Most of the codes can be read with a simple scanner, but some of the codes thrown are Mercedes spacific that can only be read with software provided by Mercedes, so it is even more important that you get that "code" information from your dealer. Good luck

 

Originally turning off the car and then starting it up again did help (even cleared the CEL), but then it stayed on constantly and I could drive fine once I got up to freeway speed and set cc. I stopped at my mechanic and they ran the scanner with me watching and I got the bad news.

 

Don't hold us in suspense........"bad news"?? Hope its not too bad........

 

The bad news was that I needed my intake manifold replaced because of the buildup and the motor (attached to the manifold) burnt out. The job was big and costly as I described up the chain a bit.