JaGa

Scanner reads misfire P0307, misfire number 7. Still lack of power. Guess I'll try to check wire seating next. See if I have plug wrench and pull plugs and check them.

JaGa

Pulled the plugs on cylinder 7. Plug B, see pic below, wasn't seated, I was able to take it out with out using wrench at all. Plug be was seated but seems dirty. Guess I'll just change them all.

ob1kenobi

How did that happen?

ob1kenobi

I'd consider you lucky for having an original CPS with 107k miles on it.

JaGa

I don't know how other than it was installed improperly to start with, and considering the last time the ignition system was worked on was by MB dealership kinda disappointing for what the guy I bought it from paid.

As far as the gunk goes I think that the gasoline has been pushing up through the threads over time and the black is from carbon.

I got new plugs now I just have to wait for it to stop raining.

Nothing like working in the parking lot at work.

JaGa

Replaced spark plugs and car sounds better and feels a little better.
I stopped to pick up my kids and ran scanner, came up with miss fire on seven and five. I cleared them and ran them again when I got home. Came up with misfire on seven and five.

I'm thinking valves on number seven are gummed up and pressure leaking out causing miss at above 4000 RPM, if I'm reading obd scanner right, and this is in turn screwing with the system around it causing other random misfires.

What do you guys think? What do you think I should do about de-gumming valves?

Nocturnal-G

I get the occasional slow start while starting the car... instead of the RPM's shooting up fast while starting, it starts up slow. Doesn't happen very often... going to guess the CPS is giving out.

What kind of plugs are you going with?

Hope this solves your issue!

Nocturnal-G

Try swapping coils and wires to different cylinders to see if the misfire follows.

JaGa

My thoughts exactly. The adventure continues tomorrow.

Nocturnal-G

Any updates?

JaGa

The car seems to be going good now. I'd have to borrow friends OBD scanner again to make sure but it pulled cleanly this morning, there still seems to be a slight lack of power on one or two cylinders but I think that will clear itself out as the Seafoam I put in there on Friday works its way through the system. Now for a list of what I did once I realized car started having problems;
1. Screamed and cursed at everyone who passed me.
2. Panicked at the thought it could be a transmission issue.
3. Got on MBworld and found some stuff about Tecron so I ran a couple cans through the car.
4. Cleaned Air sensor with air sensor cleaner.
5. Stopped on side of road found out I had forgot to plug air sensor back in.
6. Changed EGR valve, it hadn't been changed before and was bad.
7. Changed crank sensor(CPS), though I don't think I needed to have done that I will keep the old one as a spare.
8. Changed all vacuum lines I could find.
9. Borrowed friends OBD scanner and found misfires on multiple cylinders, cleared all codes.
10. Over period of several days found that cylinder seven was constantly having misfires.
11. Pulled number seven coil and tested it with a ohm meter, ohmed spark plug wires on number seven, all were good.
12. Found that plug 7B wasn't tightened properly and clogged with varnish (old gas), so replaced both of cylinder sevens spark plugs.
13. Rechecked torque on all other spark plugs.
14. Still having misfires on number seven swapped number seven coil with number two coil. Problem stayed with number seven cylinder.
15. Bought two cans of Seafoam from Autozone, threw them in tank and filled up at Exxon.

That seems to have done it. On reflection the problem seemed to have been mostly the spark plugs on the number seven cylinder, though the EGR did need replacing in my opinion. The OBD scanner was the biggest help in the end I'd suggest anyone who's going to do there own maintenance on this car get one. The one I used would cost $200-$250 depending were you get it from

snooozie

What brand name OBD scanner you use?

JaGa

Innova 3061 I think. It didn't have Mercedes specific codes but it had the ISO codes so I got STD engine/emissions codes.

JaGa

Been messing with my friends OBD scanner and still having cylinder 7 plus others randomly misfire. I also found that the middle screen I've been ignoring, I don't use obd scanners that often, gives me trim and such and here's the read out.

Fuel sys 1 N/a
Fuel Sys 2 N/A
Calc load 83.1
ECT 199
STFT B1 0
LTFT B1 -34.3
STFT B2 0
LTFT B2 -34.3
MAP (inhg) 27.4
RPM 4225
VehSpeed(MPH) 49

So since my long term trim is running way low (lean) and from looking around it seems to be the ecu on some cars act up I'm resetting the comp right now and seeing if it'll have more power on the way home. I also found how to take real-time data and O2 sensor voltage readings and I'll check the O2 when I get home, if I have time, but if this does fix the problem I might just leave O2 sensors unplugged.

The trying to run lean doesn't make any sense to me the car is getting lousy gas mileage. I might check cats to.

JaGa

Was fine for a couple miles but quickly dwindled into a slug. So as soon as I got home checked and fuel trims were running really lean again. I did another hard reboot on ECU while changing abs sensors on wife's car. I also unplugged forward O2 sensors hoping to stop ECU from adjusting trims. Took it out and BAM dang that thing goes through RPM almost as fast as my Rover burns through gas.

Quick general question; I get the feeling that a bad MAF make the fuel trim positive, and bad forward O2 sensor make ECU run lean, negative. Is this true? Or am I over generalizing.

Swear I was over 60 in just at or under 5 Mississippi.

JaGa

So on the way in today at first I was like


But then I was like



Pretty sure I ficksed it, we'll see.

SoDiezl350

I'm having identical issues as you are(sluggish performance)! Could you tell me how you determined the EGR valve was bad? Could you also describe how your car is shifting? The ECU reset on my car really improved both acceleration and shift smoothness but after a few days it reverted to laggy shifting and low power.

As far as the MAF and o2 Sensor failure modes, my understanding has always been that a bad O2 sensor results in a rich condition and a bad MAF results in a lean condition. If the MAF is contaminated, it means that more air is passing through than is being measured, which results in a lean condition.

JaGa

My EGR was physically cracked, but you couldn't see the crack without removing it. You can always block off you egr valve to try to fix/troubleshoot. If resetting your fuel trim seemed to fix you acceleration try unplugging your battery again and then unplugging your forward O2 sensors and see if the car maintains performance longer.
I live in Texas so no one really cares what you do to your car, unless you live in Houston or Dallas/Ft Worth area.
I'll probably buy new O2 sensors eventually and plug them in, or just save up for headers and ECU upgrade.
Car shifts fine as long as engine is running right, its only when the fuel trim goes lean that it starts to act up.

JaGa

So the fuel trim should do the opposite to try to correct it... I think.

SoDiezl350

That's right. Positive fuel trim indicates a lean condition.