Jack_88

I've done some searching on this one, but most of what I turn up isn't quite my symptoms. I am seeing a cylinder 5 and cylinder 12 misfire. It popped up a little over a month ago, cleared the codes, and now it popped back up again yesterday, the same two cylinders. Most of what I find indicating coils is the whole bank has a problem, and for the inverter, it seems to cause misfires randomly. Since I have one misfire for each bank, I'm a little confused. The car has 56,000 miles and probably the original plugs, so that's my first thought. Second thought is to run some Seafoam or Lucas through it in case it's just some slight gumming up of the injectors. Has anyone else seen this before or have any other thoughts? I should note, I won't be able to do any repairs myself for quite some time, I'll be enlisting friends or family to help with this one on account of my very soon to be useless arm.

ItalianJoe1

Always do plugs first. They get worn, the gap expands, and the coils have to work harder to fire under load. That's what burns up the coils.

The maintenance interval is 60k so i'm sure they haven't been done yet. Do that first and see if it improves.

Most of those Seafoam type products are a complete waste of time and money. There is no sort of baked on deposit that a little liquid can just dissolve in a few minutes.

kraut56

check out on both forums my comments on threads of this nature; the red silicone insulator inserts must be inspected/replaced.
Good luck

Welwynnick

If you replace the plugs, make sure you use 0.7mm gap plugs, not 1.0mm gap. Ignore any information to the contrary. This is critical.


Nick

DrDoe

Jack,
If you are going to get the plugs then try 20PLUS10 coupon code on autozone. I just ordered my NGK 5648 for $9 each shipped. Gap on those NGK is factory preset at 0.7mm.

My story, I replaced the fuel cap washer but P0307 still popped up. I removed the plugs in #7/#8 and found those Bosch in bad shapes . (Looked like I got ripped off as the shop charged NGK IFG6QG replacement to the previous owner 5k miles ago). I bought 4 NGK plugs but misplaced and I wasn't able to locate NGK plugs locally so I put the old Bosch plugs back in. P0442 came up but haven't returned after a week.
Today P0307 came back so I guess it's time for those plugs.

Jack_88

I have ordered the following plugs and insulators:

https://www.amazon.com/Mercedes-Benz...rds=0041591403

https://www.amazon.com/Mercedes-Spar...rds=0001590080

So, definitely the .027 inch and not the .032 inch I keep seeing. That was one of my concerns, as these come gapped to .032 inch. I assume the larger number was from before they found these things liked to toss coil packs?

Jack_88

Darn, I wish I would have caught that code before I ordered them this morning. That's okay, it's only $12.

DrDoe

Are you just doing 1 bank?
If you use the code twice then you save $44 over the 24 plugs

Jack_88

Neither of us can math today. 24 plugs, I payed 242 shipped. So, $26 more. Oh well.

DrDoe

You forgot about the two $10 gift cards

Jack_88

There were gift cards with it? Dang.

cybertronicify

There is no need for that Seaform Lucas crap. Spend the money on some quality fuel and go and give it a nice Italian Tune-Up. It really does work.

Jack_88

My problem is i have to drive the car on a 650 mile trip. When it goes into 6 cylinder limp mode, I can't tell if I'm on the freeway. I could get 100 miles down the road without knowing it's done it. Is the car okay running on 6 cylinders? I'm not sure how much the car does to protect itself.

Zach8131

I agree with doing the plugs, but ensure the shop is extremely careful removing the coil packs. They get brittle over time and can break easily. I usually have a dealer do it just so I can have the peace of mind of blaming them if the coil packs break and then they have to give new ones for free >:]

But after you get the plugs done (or before AND after) drive the car hard, with such low miles things might be getting gummed up. Take her for an illegal highway run

DrDoe

Clear your codes and your CEL should be off. When your CEL came back on you would know that it went to 6 cylinder limp mode. Pull over to reset and drive only if your CEL is off.

Jack_88

The coil pack on this car just will not go back on! My Dad is afraid to put any more force on it. We tried boots on spark plugs, boots already in coil, everything lubed up with dielectric, but they simply will not go back on. They were a huge pain to get off as well. Are we missing something?

DrDoe

I tried boot in coil and gently pushed the coils in. It gave me a scare of not wanting to in but eventually it did. I went back and forth on both end of the coil pack and didn't applied much force.

Jack_88

He got it now, here's to hoping the coil is not broken. The egr change over and MAP sensor both had hoses broken off, and this is only with the passenger side done. Nothing quite as maddening as having to watch someone else do it all. Darn shoulder surgery...I'm even having to type with one hand. The driver's side will wait until my brother can help.

Jack_88

Okay, got it back together okay. But now no turbos. No engine codes, but it's massively down on power. I don't think it's down any cylinders, but it shows about as much oomph as a Prius. Any ideas on what we may have done? Only one bank has the plugs changed, there is a new MAP sensor, and a new EGR changeover valve.

kraut56

The red boots have right way and a wrong way (upside down) to go on, but they should always be in the coil pack tubes, not already on the plugs (the smaller diameter end down to go onto the plug); and then just slowly even pressure along the pack.
If you have no boost I guess a sensing line is not hooked up or blocked.

Jack_88

Okay, after rechecking the seating on the alloy pipes and tightening them(which was needed,) it's still way down on power. We unplugged the battery to clear the computer, and it seemed like it takes off the line better, but other than that, it's still really down. It feels like everything is normal, just completely without turbos.

kraut56

you need a DAS readout

DrDoe

Jack, Did you drain out the residual coolant in the intercooler? I didn't and wonder if it would make a difference in the turbo response.
Just finished the driver side plugs change last night. Going after the passenger side next.

Jack_88

I left the coolant hoses attached and it was propped up during the change. Other than that, it wasn't touched. Should it have been?

DrDoe

Then nevermind. I thought it might need to be primed.