jnm4jko

Hello all...I am new to MB and to this forum and have a question hopefully some knowledgeable person can help me with. A little history; 2006 c230 146xxx. I bought the car knowing that it had a random miss; drove it almost a month before there was any sign any trouble. DTC codes; 0030, 0300, 0304, 0306. It has all new OEM plugs, new MB coils on 4 and 6. Clear the codes and it's the same.

Now here is the strange thing (at least to me)...The first couple minutes upon startup it doesn't miss AT ALL. It drives and accelerates perfectly. As soon as it goes into closed loop, it runs like complete crap. You can cycle the key on/off, it runs fine for 30 seconds or so then its back to crap.

Here is what I have checked:
1. The grounds under the hood are tight and free of corrosion and look good to me.
2. I believe the Ign Coils are internally grounded to the head. Those grounds t30 bolts are tight and look good.
3. Replaced coils and plugs; reset codes and this is where I am currently at.

What are your thoughts?? Is there anyway to test for a failing ECU?

Thanks in advance!!

Justin

ildd

Sounds somewhat similar to what I experienced a few months ago. I brought it to a local shop and they were pulling their hair out for almost a week before calling a Mercedes hotline. If I understood them correctly, they got on the highway, went 50 mph, put the transmission mode to "3" (bring the stick to the left twice) and drove for 30 seconds. Apparently that fixed the problem and I've had no problems since.

Of course, you should probably wait until Glyn comes in here

jnm4jko

Update: Unplugged MAF; no change.

If it's as simple as what you have described I will be extremely happy and surprised. Any other thoughts?

Any point of swapping the injectors off 4 and 6 to the other side??

jnm4jko

More food for thought...DTC 0030 is on the Bank 1 side (1-3) but the misfire is occurring on Bank 2 (cyl 4&6). The misfire causes at least one cylinder to deactivate which you would think would be detected by the Bank 2 o2 sensor. I looked back at the maintenance records; Bank 2 front o2 was replaced roughly 100k miles ago, no records on the driver side which leads me to believe it hasn't been changed as the previous owner kept every service record. Has anyone ever seen an o2 act up and never trigger a DTC read by the computer. I ordered two new MB 02h's which should be here tomorrow. Any other thoughts on this?? Thanks

jnm4jko

Oxygen sensors came in today; I replaced the passenger side first; the DTC 0030 is gone but the car still is missing once it warms up. Its not throwing any codes now but I didnt drive it, just left it idling in the garage. The driver side o2 looks awful to get to (big hands and MB are not friends). I do not want to replace this unless someone can make sense of why/how an o2 could fail, cause mis-fires on 4&6 (not on 5). Is there anything else I should look at? Is there anything I could do to eliminate the driver o2 sensor from being the culprit? Like disconnecting them and forcing the car to stay in open loop. Has anyone ever had a failing o2 sensor NOT throw a code despite being faulty? Still trying to make sense of this. Thanks again.

jnm4jko

Any MB mechanics have any thoughts?? I have still have 3 DTC codes: Random Misfire and dead holes 4 and 6 (0300, 0304, 0306). Most whom have this issue replaced plugs/coils etc and the problem was resolved. I have looked at wiring, grounds, removed/inspected MAF/TB, replaced Pass Side front o2, swapped plugs/coils. The misfire will not move cylinders. The car runs perfect in OPEN LOOP. . Is there any sensor/known issue that I should be looking at? Looking for some suggestions...please and thanks.

Glyn M Ruck

Hmm! It is almost as though fuel supply is being cut to injectors 4 & 6 in closed loop.

Lets go back to basics. We need fuel, spark at the right time & air.

- Make sure the airbox is clamped down tightly over the MAF (frequently left loose on M272) causing the MAF to hunt.
- Make sure air cleaners are clean
- The M272 is coil on plug. Make sure that the engine harness wires to the coils are OK. Clean ECU plug with switch cleaner.
- Check the CPS. A failing CPS can work perfectly cold & fail when it heats up. Pour cold water over it.
- Check fuel pressure at the Schrader valve on the front fuel rail that connects the injectors. s/b > 3.8bar or 55psi. If low suspect fuel pump or clogged filter.
- Add Techron Concentrate to a tank of fuel at recommended dosage to ensure that both injectors are flowing at correct rate.
- Check compression on cylinders 4 & 6

You might have a MAF issue but I would expect fuel trim codes.
If an O2 sensor is cycling too slowly I would expect a code.

Good luck!

jnm4jko

Alright, this is what I have thus far:

Compression 1-6 (DRY) 150 +/- 2
Fuel Pressure (Key on): 55 psi
Air Filters New
Air box is where it needs to be; nice and tight sitting squarely on the MAF
The IC connectors are clean/no oil. I will have to pick up some switch cleaner.
Key on: Battery voltage on Pin 1, signal on Pin 4

Haven't added Techron or checked CPS. Wouldnt a CPS issue be more of a no start OR misfires on both banks? Is there anyway to test a CPS?

I have been wrong before but everything is pointing to something electrical/wiring/sensor related and not something mechanical/fuel related. I have sorted through those issues on other toys of mine; something is causing the ECU to cut fuel or spark after the car transitions into closed loop.

I have a buddy that is a master at Swope BMW; he keeps saying ECU. I have another buddy that owns a shop that builds racecars and he is leaning towards cats/o2's. Obviously with the mileage the cats may be heading south, but why no codes and why not on cylinder 5? These cars are quite complex and I don't want to throw money at it unnecessarily. Keep the ideas coming...thanks again.

Glyn M Ruck

There is no way to test the CPS other than cooling it. I would expect high temperature starting issues but possibly not cold.

Does your temperature gauge operate reliably?

You could have an engine harness issue. Cats are an unlikely source of issue unless clogged & even then why on those cylinders???

I think it is time to get this car onto a Star for complete diagnosis.

jnm4jko

After posting this question on another MB forum someone brought up something that made me think; it could have been possible to have a knock sensor issue sending false readings back to the ECU forcing the ECU to shutdown those cylinders. SO...the night began pulling the intake, swapping Bank 1/2 knock sensors; switching the injectors off 4/6 with those on 1/3, adding Techron, CRC'd all connectors, cleaned MAF/TB with app solvent, split the intake/inspected the plastic flappers and resealed the intake with BMW gasket maker...LONG NIGHT.

The outcome: Car still is doing the same thing as before except NOW I have the random misfires on 4/5/6 which is music to my ears. I'm thinking the convertors on the driver side my be going. I am going to either do a back pressure test with the o2 out OR drop the exhaust on that side and see if the misfire goes away. I consulted with a independent MB owner today and I ran my prognosis by him...hopefully it's the CAT and I can move on with life. If this turns out to be a false lead THEN off to the Indi I go. I just hate spending money when I am fully competent to do the work they are going to do on my car. Any thoughts/suggestions?? Thanks.

Glyn M Ruck

Not the knock sensor. Reaction to the knock sensor is global and results in timing being retarded not fuel supply shut down.

jnm4jko

Good point Glyn, do you think considering all cylinders on Bank 2 are misfiring a catalytic converter could be the culprit?

Glyn M Ruck

A clogged Cat could be the problem.

Holmes5518

Easy quick check to see if the cat is plugged is with an infrared thermometer. Point it at the front of the cat and then the rear. Temps shouldn't be too far off. On a clogged cat the piping before the cat will be far hotter than after the cat. You can compare to the opposite side cat for reference temps.

jnm4jko

Good point with the IR, only if I had one This morning I begrudgingly pulled the driver side o2 sensor out and replaced it with a new OEM one, which apparently caused the random misfires I was experiencing. There were no fuel trim codes or any codes for that matter that suggested that was or could be at fault. Either way; I put roughly 50 miles on it today with no further issues. Hopefully this was the fix.

The only slightly odd thing is now, considering I pulled the intake which required pulling the fuel rail, I now am having a slight problem on the first start of the day where the car turns over much longer than previously before it starts. Almost feels/seems like a fuel pressure problem. Looks like I will be checking FP again. Hopefully this is an easy fix.

Glyn M Ruck

+1^ Good tip.

Glyn M Ruck

I hope it's fixed. Strange ~ O2 sensors usually throw codes.