sts2f

Seeing as no one seems to have an answer to my other thread I figured I'd ask it in a different light. I'm getting five codes from the CEL:

P0100 - mass air flow circuit (x2)
p0300 - random misfire detected
p0302 - misfire cylinder 2
p0305 - misfire cylinder 5

Given that 2 and 5 are both middle pistions on each bank I'm inclined to think there is a common wiring or relay for these two that may cause the issue. The only other question would be can the MAF sesnor malfunction be causing these misfires? Thanks!

RobertG

Fix your mass air flow first before you chase the misfire issue.

Glyn M Ruck

+1^ P0100 = Mass or Volume Air Flow Circuit Malfunction.

Make sure that the airbox is clipped down properly & sealing over the MAF. Sometimes a problem particularly on the M272 engine.

Clean or replace the MAF.

Then check plugs & on-plug coils.

sts2f

Heres my issue, i've done all that several times (changed plugs, moved coils to new cylinders, ran car with MAF unplugged). The thing that makes me suspiscious of it not being the MAF is that the "alternator/battery see workshop" warning came on like 10 minutes before this started happening. Looking over the wiring diagrams it seems like i may need a new ME-SFI module if a spike in voltage happened and the module got fried. The battery I just changed out after the warning came on was the original from 2006. My logic for this is as because out of the five wires coming from the MAF none of them touch bank 2 injectors or coils. The wires breakdown like this (check me on this if you have a diagram too):

Blue/Violet wire goes to pin 93 of the ME-SFI
Black/Grey wire goes to pin 69 of the ME-SFI
Brown/Violet goes to pin 17 of the ME-SFI
Black/Red goes to pin 67 of the ME-SFI
Red/Grey goes to injectors 1,2,3 and the right intake camshaft hall sensor as well as the right exhaust and intake camshaft solenoids.

So this would explain somewhat the misfire on 2 but not 5 nor the "iginition coil e primary circuit low" (code p2303) that has popped up and disappeared. The only wire that splices into every coil is the red/blue wire that traces all the way back to fuse 53 in the front SAM (also connected to engine circuit 87 relay). Does that make sense? Anything I'm overlooking as to how the MAF could cause the cylinder 5 misfire whether it be by faulty fuel injector signal or coil signal?

Glyn M Ruck

The MAF is unlikely to have anything to do with the misfires. If it did you would get a fuel trim code due to is throttling back the injectors on those cylinders.

I would replace the MAF or borrow a known good unit. I'm pretty sure you have a cooked MAF. Even when MAF's fail they seldom actually throw codes.

Spurious alternator/battery warnings are not unknown. See vixen's thread.

sts2f

If the MAF is not causing the misfires then it doesnt seem to be the urgent fix. The plugs are brand new, ran fine for a 250 mile trip right after I changed them. Coils arent the problem as I switched them with misfires staying on the same cylinder. With only those 4 codes to run off of what would the next common cause be?

Glyn M Ruck

You have to sort out that MAF for the sake of proper mixture control ~ once mixture is correct it will help everything. If plugs & coils are OK next thing is injectors.

Please also take a look at your inlet manifold & make sure you have no broken flap rods or pivots. Early manifolds were troublesome on the M272.

You might have numerous things contributing to misfires. e.g. lean mixture & dirty injectors or lean mixture with borderline coils etc.

Moviela

Random misfires are usually the result of comtamination. Let's explore how misfires are detected. The computer sends a signal to the coil pack based on the factors it has evaluated from various sensors to fire the sparkplug. When the plug fires the current in the secondary creates a flyback pulse that is read by the computer. This flyback pulse makes a statement of how well the sparkplug did in igniting the fuel. Ain't electronics wonderful? The pits in the path of progress are leakage currents in the primary or secondary of the coil packs. If the problem is insulation failure inside the coil pack, it needs to be replaced. If the problem is external that can be fixed. It is important that the output to the spark plug be hospital clean. All the current wants to be delivered to the contact on the plug. Any grease, oils, dirt, grime, or other comtamination can allow arcs or corona to reduce the spark. When changing plugs it is a good idea to wipe the bores in the head with solvent to make them tidy. After the spark arrives at the tip of the plug, it needs to get back. For an instant the current is very high and needs a low impedence path to ground. This is acomplished through the threads of the plug AND a heavy cable between the engine block and the chassis. It is important that the block to ground cable be shiney and tight. The torque of the plugs is also important. If they are not tightened to 23 Nm the job is not done.

The MAF sensor is usually a thermistor sealed in glass. It measures the amount of air flowing into the engine. It does this by passing a current through the pellet, heating it slightly. An electronic amplifier reads the current flow in the thermistor. When air passes over the device it slightly cools the pellet. More air, more cooling. This causes a change in the current, but it is a teeny tiny change, and a very high impedence circuit is needed to read it. Oil or dirt on the outside of the glass will interfere with the work of the amplifier. The sensor get contiminated by oil saturated filters, leaks of air beyond the filter, or even a finger print on the glass. MAF cleaner does a great job of cleaning the contaminates, but if the thing has been dirty a long time you might not be able to clean it.

Last item on the list is clean fuel. Fuel filter of course, but also the use of top tier fuel will reduce the chance of injectors being clogged. Gasoline is not gasoline. The detergent additives in top tier fuel are more active than those of other brands, even if they fill at the same rack as the top tier marketer. Techron is probably the best additive, but other brands are OK to use without reservation.

Glyn M Ruck

Wonderful dissertation Movie.

Giving the plug threads & connector a light wipe with conductive compound can help.

RobertG

Misfire is detected by the cps, if you are not getting good info to the ecm from the maf, then you will not get proper amount of fuel to the cylinders and that leads to a misfire.
Here is a good explanation ;http://www.underhoodservice.com/issu...ontentid=71962

Glyn M Ruck

Benz uses an ion-current sensing system of misfire detection that is far more effective at detecting misfires than engine systems that use the crankshaft sensor/speed analysis detection method. Movie is correct.

RobertG

Yes both of you are correct about mercedes misfire detection, I was just trying to simplify the explanation about misfires in general.
here are some examples of misfires and causes; http://www.autoinc.org/archives/2009...9/techtips.htm

sts2f

Thanks for the info guys, just to confirm piston 2 is the middle piston on the right bank correct? The wiring diagram I have is kind of cloudy on it and shows it as the last piston (see image). Also I attached all the codes I'm receiving now. I replaced both cam sensors on bank 1 yesterday and the p0012 code came after that.

Glyn M Ruck

sts2f

thanks Glyn

sts2f

did some research on the p0012 and thinking it might be the magnets instead of the cam sensor.

Glyn M Ruck

Definitely magnets. See long thread that Johnand & I worked on to sort out this darn problem.

Glyn M Ruck

Here:

https://mbworld.org/forums/c-class-w...-bank-1-a.html

RobertG

??

Glyn M Ruck

Read right through the thread. We took a while to figure it out.

Glyn M Ruck

What is your question?

RobertG

Why would you tell him to replace the maf if you say that it has nothing to do with misfires?

Glyn M Ruck

Robert. You can be obnoxious on the OT but don't even think about that nonsense here. We have different rules for the Tech forums. If you have nothing useful to post take a hike.

He is experiencing a P0100 = Mass or Volume Air Flow Circuit Malfunction & I recommended MAF cleaning or replacement. P0100 in my experience almost always means a damaged MAF. Harness failures are not common on the W203 M272 engine.

One thing I can say without fear of contradiction is that I know more about Benz vehicles than you do.

RobertG

what are you talking about ?

I'm being obnoxious, asking a question?
even thou you agreed with me about the maf sensor being at fault?
calm down and explain why you went the cam sensor magnet path even thou the initial diagnosis was maf.
You dont have to school me on the rules of this forum,
if you need a hug then say so

Glyn M Ruck

Have you read this & the OP's previous thread ~ obviously not. The OP was messing around with cam timing codes which were not the topic of this thread.

You obviously do need coaching. Tech threads will be handled like the schoolroom & the OT like the corner bar. Decision made over a year ago.