1996 E300D misfire with OBD code P0200 - PeachParts Mercedes-Benz Forum

Maximan1 · #1 09-27-2019, 03:19 PM

Hey guys,

My dad asked me to take a look at his car today, it's a 1996 E300 with the OM606 naturally aspirated engine. It was having an intermittent issue, but it did not go away during my drive to work today. A rudimentary OBD2 scan shows code P0200 for the fuel injection circuit being open.

I know this can mean several things - I want to see if I can narrow it down just via the symptoms.

The car idles smooth and emits no smoke when idling. As soon as you put your foot on the accelerator it will start to smoke and cough. Car will not go over 20 mph, floods out the entire street with smoke.

Am I correct in assuming this is related to the fuel rack position sensor? I don't currently have access to a Mercedes scan tool.

Diesel911 · #2 09-29-2019, 11:36 PM

What color is the smoke and does it smell like Fuel or burned Oil.

On the earlier models the rack position sensor controls the EGR system.

Maximan1 · #3 09-30-2019, 03:29 AM

The smoke is white with a blue tint, smells mainly like diesel but I can also smell oil in it. I think the EGR has been blocked off on it - there is no line from the manifold to the EGR, just a cap on the manifold - but I am not very familiar with these engines.

The rack position sensor is what I think may be the culprit, since the car idles perfect but can't rev up.

Also, correction - the car is a 1997 not a 1996.

engatwork · #4 09-30-2019, 07:12 PM

Give us some mo info. Has the car been sitting? How many miles are on it? Have the delivery valve seals been done? How does the engine air filter look? White smoke means coolant to me.

Maximan1 · #5 10-01-2019, 01:16 AM

Mileage is around 260K, I will check exact mileage tomorrow. The car has not been sitting, it is my dad's daily driver. Delivery valve seals have not been done since we have owned it (4 years). Air filter is clean and relatively new. I would agree on coolant but the smoke does not smell like coolant, does not leave droplets, and I found no other issues suggesting it's a head gasket.

The car is definitely running rich at some points, I revved it up today and it left a black soot spot on the ground.

Maximan1 · #6 11-13-2019, 05:36 PM

So I had my local Indy shop read the codes and it came back with P1475 for the y22/6 switchover valve and P1470 for intake pressure. I then took the car for a slow, smokey drive and noticed embers falling on the road behind me. I pulled over and looked under the car and discovered that the cat/trap oxidizer was almost glowing it was so hot.

Spent the last couple of days pulling off the exhaust, cutting out the cat/trap ox, and then replacing it with some lengths of straight pipe. I also discovered that the trans is leaking a little bit.

With the new "cat bypass pipes" installed and trans fluid topped off, the car is running and driving normally again. My theory is that the cat was clogged so bad that when the engine was revved up, the exhaust gasses had no way to exit the combustion Chambers and were being forced back out the intake valves when then opened, causing the misfire and the P1470 code. The fuel that was injected was going into the intake, causing the P1475 code (I still need to clean the switchover valve), and some would also flow down to the cat, causing the excessive smoke and causing the cat to get even hotter.

Seems to be back to normal now. Hopefully if anyone else has similar issues, they can see the conclusion I came to with this problem.

valvecovergasket · #7 11-13-2019, 06:00 PM

props for coming back and updating once you found the issue

hows the exhaust sound now? any more drone on the highway?

Maximan1 · #8 11-13-2019, 07:41 PM

It may be slightly louder, but you cannot tell from inside the car. No drone to speak of.

This car has so much insulation compared to the W123 - with open headers, the interior was still quieter than the straight piped OM617a in my 240D.