Gabe

The engine pictures included in this thread show some vacuum hoses. First of all, they have to be made of stiff plastic or thick walled rubber or they would collapse with the vacuum pressure. Second, they can either be white/translucent or black and the MB ones will have connectors that are thicker than the outer diameter of the hose.

Find the picture above that has a small caption that says, "Remove Circlip and Hose - Remove FPR". - the circular shiny element is the Fuel Pressure Regulator and a black vacuum hose is connected to it. Right underneath the black hose you will also see a white/translucent vacuum hose. Those are the two examples.

If you follow the white/translucent hose you should notice it starts somewhere in the air intake system of your engine compartment. Air flowing through the intake creates lower pressure and that is where the vacuum originates. Faster engine RPMs means more air flowing in and a proportional increase in vacuum. Many subsystems around the engine (Fuel pressure, transmission shifting, etc.) rely on this analog control.

Spark Plugs are not very expensive so you should also consider getting a different/better set if you are confident that you torqued them adequately (I belive only 1/4 turn after seating) and the electrodes are in all-the-way. Another idea is using a Fuel System Cleaner like a Ventil Sauber, Valvoline or other quality cleaner.

Good Luck,
Gabe.

plisken

how did u take off the regulator?

plisken

how did u take off the regulator?

jhavron

Got same probs. Thought it was the TPS at first, but from my experience when these go bat it is usualy in a couple of spots in the throttle range. Unhooked the vacume line to the regulator on the fuel rail and plugged the line then drove to town with no change. Don't know if I was suppose to see a change (good or bad) but I didnt.

mpetersen

My 99 C280 has this same problem. I drive twenty miles on the highway hit the off ramp and at the light the car starts stumbling. I have lived with this for about a year but recently I received the CEL with the bad behavior. The codes P0302 which sounds familiar. My issue may be related to a general electrical system wig out which goes along with idling after the highway run. Usually exacerbated by headlamp use.

Eder Didier

Hi, i had the same problem in my w202 C230k '98. if i hit the gas hard the rpm go up but the car does not accelerate and when i arrived to a stop light the car is stumblng but if i turn off the car and power back on it works correctly ,so i had to accelerate smoth and the car runs fine. i change the spark plugs, the coils, make all the oil and filter changes i add benz injector cleaner but still has the same problem. im reading all your post and i dont know what could it be. MAF? catalytic converter? O2sensor or the fuel pressure regulator ?

Help !!

SORRY FOR MY BAD ENGLISH

JD Fine

I have the same issue on my 99 C230k. Replaced vacuum lines with no results. Wondering if you found a solution?

heespaul

My experience has been that the problem that burns plug wires, ends of plug wires begins with someone not getting plug wire onto plug properly. This causes arcing from wire trying to get fire to the plug. But what is worse is it causes the coil packs to over heat due to an incomplete circuit. When you have a misfire the engine light should come on. Take it to Auto Zone and get a IBD code readout. That will tell out where the problem is. Coils packs take about 15 minutes to change. always start with the basics. An internal combustion engine needs 3 things to operate. Compression, fuel, and spark.
Seldom will fuel cause a sudden rough running situation. Mercedes fuel systems either work or or not at all. Checking for fuel at the engine is simple. Slowly crack the supply hose at the fuel distributor. If there fuel then you know its getting to engine. You can test the coil packs using a OHMMETER. Find how to use the resistance testing. You an find this procedure online or YOUTUBE. research what the correct measurement should be for normal coil pack. Coil packs are around $60 and up.
Hope this helps, Paul

Ben.martin14

khomer2

Ben,

You should start a new thread, not add to an old one.

Seems all of your misfires are all on one side PO304-Cylinder 4, PO305-Cylinder 5, PO306-Cylinder 6.
Possibly the coils that the wires plug into.
P0170 is all about that (MOT) valve (located behind the DS headlight if I recall.) Remove it and clean both openings with some carb cleaner and let it dry before reinstalling it.
P0150 is your o2 sensor. may need replacing.
P0442 is small evaporator leak. Might be as simple as replacing the gas cap.

One step at a time and scan each time after to see what codes come back.
Also, do a search on the forum here. There's a wealth of information on these codes you can read up on/review to tackle yourself.