E320 Misses at load or low RPM-New Coil-boots and F8DC4 Plugs
 

EDIT:
I think I have it figured out. Bad wires. I haven't changed them yet because I just also figured out I believe the car has a bad head gasket. It white smokes when hot and driven hard.

But last night I decided to work on it for a second and noticed (it was a VERY dark night) while running that I could see arcing through the plug wires. It was faint but there were sparks through the insulation to the valve cover on all 3 wires (or at least two of the three). Also, the number 2 or 3 *the one with the plug wire can't remember* boot on the plug was easy to see that it was arcing to the valve cover whenever there was a mis. So......... seems like I've found the problem.

At this point I'm guessing the common failure of plug wires is the die-electric properties of the insulation. Maybe a ton of electrical tape would fix that! Of course the real fix is to just change the wires.

But on to bigger things. The head gasket!











I just changed as much as I could on my new E320 (Edit 1994 Model) to address a mis. I'm still getting a mis fire after:
-F8DC4 Bosch plugs
-3 NEw Coils
-3 New boots under coil
-REplaced OVP fuse

Getting code 13 consistently and a 4 once in a while.

I noticed the EGR will not hold vacuum (none at all).

Could the EGR be stuck open? Would that cause a misfire?

What year 320?

Sorry this is a 94. Forgot to put that. M104 3.2 6 cylinder.

what shape is your engine wiring harness in? Have you inspected the insulation?

Jonathan

I'm assuming that's the cloth tape wrapped bundle that powers the low voltage side of the three coils. I peeled a little of this back between the head and the firewall and what I saw looked to be in good condition (no flaking and felt rubbery still with no bare wire exposed).

E320 MISS
 

From experience,I can tell you that if your wiring harness has not
been replaced you will be throwing money at that thing until you
are broke.You can do it your self in about 2 hours,with lemonade
on the side!!Make sure you get the right one for your car!!http://www.peachparts.com/shopforum/...ons/icon10.gif

Just a question, why would load or lower/faster RPM be affected by a bad wiring harness? It seems like a bad wire connection would be either all or none wouldn't it?

The correct Bosch plug for this car is an F8DC4. You list another plug with an "R" in the designator. I'm not 100% sure but I believe the "R" stands for resistor. If you have resistor plugs installed, they are most likely the cause of your problem.

J. M. van Swaay

These are actually F8DC4. I have a couple of cases of them and made sure they were infact the Non-Resistor plug. Typo on my part. But yes these are the F8DC4.

I was going to suggest that it might be a bad coil until I reread that you changed them already. On what pin number do u get those codes?

It was pin 8.

I think I have it figured out. Bad wires. I haven't changed them yet because I just also figured out I believe the car has a bad head gasket. It white smokes when hot and driven hard.

But last night I decided to work on it for a second and noticed (it was a VERY dark night) while running that I could see arcing through the plug wires. It was faint but there were sparks through the insulation to the valve cover on all 3 wires (or at least two of the three). Also, the number 2 or 3 *the one with the plug wire can't remember* boot on the plug was easy to see that it was arcing to the valve cover whenever there was a mis. So......... seems like I've found the problem.

At this point I'm guessing the common failure of plug wires is the die-electric properties of the insulation. Maybe a ton of electrical tape would fix that! Of course the real fix is to just change the wires.

But on to bigger things. The head gasket!

Don't jump to conclusions yet about the head-gasket although it is a possibility...

Smoke could be:
1-Transmission overfilled draining through the vent on the exhaust ..check the level.
2-Valve cover towards the rear of the engine leaking oil down on the exhaust
3-Head-gasket as they do leak in that corner, also down towards the exhaust....

Degrease the engine big time...and drive it for a while......you would be able to see the location of the leak....in reference to your other question, the heads don't usually crack, and seals don't usually wear on the m104, unless horribly abused.....

good luck

Headgasket failure on this engine commonly causes external oil leaks. Loosing coolant into the cylinders is not a typical M104 failure mode. Does the exhaust have that sickly-sweet glycol smell?

I say get it running right and drive it for a while, monitoring the coolant level. White smoke could be a chilly night and/or a crudded up motor from the misfire.

It sounds like from what you describe, the smoke would be from near the engine or mid exhaust. This cloud of white smoke is coming from the tailpipe. I'm sure hoping that it's not a head gasket.


All I know is the exhaust REALLY stinks. It doesn't have the typical rotten egg smell of unburnt fuel anymore. It has a strange smell that I haven't smelled before. I wouldn't say a sweet smell. Hard to describe the smell pretty hard to handle though.


I was getting a code 13 (running at lean or rich limit on Lambda IIRC) but would a misfire cause this?

Well I just ran it again... this time I electrical taped around the boot on the offending plug wire and it ran near perfect. The miss was 99% gone. I still hear that it could be a slight bit stronger and smoother. I'm going to tape around the wires too since I saw a voltage leak on the insulation when I watched in the dark last night. That should cure it for now. I'm not sure how long term this fix will be but I wanted to figure out that this is the fix before I put a dollar more into the car.

And weird... but the smoke was gone. That's nice! But I wonder if it will come back after running for a bit. It was on and off before. I'm a little baffled by it.

What's interesting is that this car has as much get up and go on 4 and 5 cylinders as my OM603 in my 87 300d has on all 6 with the ALDA removed. Kind of fun to drive after the car is running right.