Koolkozak

Hi folks, I have a 2010 c300 4Matic Sport with 92,000miles. I left it in storage for about 2 years, because I didn’t want to drive it without changing the transmission oil that was due (I did the first change around 50,000mi). So I was driving my wife’s car for a couple years while I neglecting this thing.

Now I wanted to get this back on the road, put in a new battery because the old Bosch died and was not able to be charged at Autozone, filled with 5 gallons of fresh Shell 93 gas and it started right up…but with moderate shaking and misfiring. I hooked up the scanner and it shows bank 5 and 6 misfiring and P0300 Multiple banks misfiring.

I had just changed the spark plugs and coils at 85,000miles before the long storage and it had been driving fine until I left it sitting 2 years ago.

No evidence of mice or squirrel nests.

Could it be gunked up gas tank or water in the tank? The car was almost on empty before I put in the fresh 5 gallons.

Could it be something with fuel injection or air injection?

Any opinions appreciated and how to diagnose or what I can do to get it firing right, maybe starting with the easiest diagnostics first to rule them out.

thanks much

TimC300

I would put a bottle of Techron in the gas tank, just to clean the fuel system in general after having the same gas in it for 2yrs.

Can always try swapping the coils, inspect the plugs while you're at it. Probably not the issue but never know.

Im thinking maybe dirty injectors from the gas.

How bad is the shaking and misfirring, is it driveable? Tried revving it, get the new gas cycled through?

JettaRed

iTrader: (1)

How long did you let it run? Was the CEL flashing or steady? If you have bad gas in the lines, it will take a while to get it out. Are those the only codes?

Odd Piggy

All the suggestions are valid ones. It’s probably going to take a while to get the new clean gas and additives through the fuel system.

Since you were able to fill it with new gas, it was probably below ½ tank in storage. With no fuel stabilizer in it, 2 year old gasoline has lost all of its volatiles. That’s what makes it atomize correctly so it burns evenly. And the ugly thing about gas tanks is that they will let air in to avoid collapse but won’t let anything out. So any temperature change, even if stored in a garage, creates condensation which eventually makes its way to the bottom of the tank.

I suggest doubling up on that dose of Techron or also adding s bottle of gasoline (not diesel) fuel system water scavenger.

If it doesn’t recover after 100 miles or so of driving, consider just changing the spark plugs. Even though they only have 7000 miles on them, they’ve been sitting in a cold, hostile environment for 2 years.

Koolkozak

Thanks fellas, the fuel system was my concern too. I’ll try the Techron as you suggested. I have no experience with it, any particular type I should use, and any particular procedure? Or just pour it in and drive?

How about that water scavenger product, red bottle isoHeet water remover and injector cleaner? Is that the same as Techron?

Also, any damage that can come from driving on 2 banks misfiring while I’m trying to cycle the bad gas out?

Koolkozak

I ran it for about 5 minutes before I shut it down and stopped the codes and got multiple misfire and bank 5 misfire. Started again for about 5 minutes and then bank 6 popped up also after that.

the shaking is not violent but enough to know that misfire is happening.

the CEL flashed in the beginning a few times and then stayed on constant. Is there a difference between the two?

TimC300

Techron just put it in the gas tank when you fill up.

If there is a Napa auto parts near you its on sale this month, both the regular size bottle and the value size. I get the Value size, get 2 fill ups out of it, or two cars.



I dont have any experience with water removers. I read the Red HEET is for removing water in the tank. But I also read that the ethanol in gas will also absorb water. No idea.

TimC300

I always thought if the check engine light is flashing that means pull over right away and stop the car, dont drive it.

TimC300

Can you check fuel pressure with your scanner, my scanner will show fuel pressure.

I think fuel pressure should be around 55psi.

Do you have a Mercedes specific scanner?

Koolkozak

No my scanner is a regular simple obd2, no pressure readings.

thanks Tim, got Napa downtown 👍

Odd Piggy

Use the regular Techron concentrate. It’s a gasoline “detergent” similar to what’s blended into what you buy at the pump, but a higher concentration (Chevron says 10x) to remove deposits. It won’t fix a broken engine, but in your case I think it’s applicable.

Use the yellow HEET because if you’re using the Techron, you don’t need the injector cleaner. It’s basically dry methanol, which Mercedes limits to 3% concentration, so you’re fine with the 12 ounce bottle.

TimC300

How does the exhaust smell, normal, like gas? Any smoke?

Check the oil and coolant, see what each looks like.

May be worth pulling and inspecting the spark plugs.

May be a good idea to look into a Mercedes specific scanner. I have a $15 Konnwei obd reader that works great and was able to diagnose and fix two cars with it, but my Foxwell with Mercedes specific software does so much more. It was showing codes that never showed up with the reader. Can rule out alot by having one.

if you inspect the plugs it would be a good time to inspect the air filters, inspect all the hoses and vacuum lines under there. When I replaced my battery there was an animals nest down at the battery tray. Looking at the Carfax for my car it looks like the car was not used for an extended time prior to me buying it.

Im wondering if theres a way to drain some gas to inspect it. there is a schrader valve at the end of the fuel rail, wonder if it can be removed, turn the car to "on" and it would pump out some gas to see what it looks like.

Also in my maintenance manual for my 2010 c300 it does have replacing the fuel filter around this time. May be clogged. Seeing fuel pressure would come in handy.

JettaRed

iTrader: (1)

CELs are related to emissions problems and will provide a P0XXX code. If flashing, it means you have an immediate malfunction that is harmful to the environment, such as continuous misfires. A steady CEL is also a sign that you have a problem that affects emissions, but not as serious as when flashing. A CEL will not show for something like a faulty wheel speed sensor -- there are other lights for that.

Koolkozak

Ok I should try Techron and the yellow HEET both together with the 5 gallons of Shell 93 gas that I filled up with?

Any thoughts on combining them? Or should I just try Techron on its own?

Is there a procedure to siphon some fuel through the fuel rail shrader valve to get some of the Techron/HEET treated gas in to the injectors quicker?

JettaRed

iTrader: (1)

What engine do you have and/or do you know if it is direct injection (i.e., does it have a high pressure fuel pump)?

JettaRed

iTrader: (1)

Yes. See attachments.

Koolkozak

Not sure exact engine code, but it’s a 2010 v6 4Matic Sport US Version. Not sure if it’s direct injection or high pressure fuel

thanks for those, but theyre a bit too high-tech for me to follow. I’m pretty hands on and stuff but I think those are more for a professional daily Mercedes’ mechanic.

TimC300

Probably same engine as mine, M272. No HPFP.

As for getting gas through the line faster you can disconnect the fuel line at the fuel rail. Turn the key to "on" and it should continue to pump fuel. DO NOT START THE CAR. It may be messy, line will be under pressure so be careful disconnecting.

Ignore the red arrow, the fuel line from the gas tank is the steel braided line below the arrow.



If it were me I would want to check the condition of the gas. I work on small engines alot and see what gas even a few months old can do. I bought two used pressure washers from lowes, customer returns for $25 each sold "Parts Only". Lowes told me they would cost too much to fix. Got them home and turned out it was very stale gas. It looked dark brown and smelled horrible. Inside of the carbs had a greenish scale/corrosion all over the metal, the pilot jets were completely blocked and i had to unclog the holes with a thin wire. A fuel system cleaner would not work in that case. I drained all the gas, cleaned the tanks and carbs and they ran like brand new afterwards.

May be easier to try and siphon some gas from the tank, thin hose down the filler neck. Liquid transfer pump would be great. If the gas looks and smells fine then great. But if not it may need to be removed. I would hate to see even more damage done if it is stale gas, can really mess up things like the cats, O2 sensors.

Koolkozak

It was very low on gas, so I added 5 gallons of fresh Shell 93 Nitro power gas. I’m sure there’s either water or nasty crud left over from the old gas.

Im more concerned with the fuel rail/injectors clogging. I think the fuel lines should be ok. Would be nice if there was a quick way to flush the fuel rail, I thought it was possible through the shrader valve at the end of the fuel rail.

any thoughts about using Techron at the same time as isoHeet?

should I just pour in the Techron and let it sit overnight and then try starting in the morning?Or pour in and start it right away and let idle for a few minutes?

Odd Piggy

There’s a fuel filter between the tank and the injectors. It should catch any debris. I think all MB fuel tanks are plastic so solids accumulating in the bottom are not common. Water is the main worry on a stored car.

Go ahead and use the HEET with the Techron. It won’t hurt, it might help, and it’s $3. Just pour the two in and drive to fill the tank with more 93 octane if it’s not full. If full, drive around because you want the additives to mix with the gas.

Caution on driving: take extra care if the misfires are causing hesitation on take off.

If you have a hose with a fitting that fits the Schrader valve, you can purge it like that, but I’m not a fan: the fuel pump puts out 30+ PSI and gasoline going everywhere is a real hazard.

TimC300

I dont see a reason to not put both products in the gas tank at the same time.

I never messed with the fuel rail before, but im assuming you can remove/unscrew the Schrader valve and flush the gas that way. From Pelican parts it says to release the fuel pressure just push the valve in.

- Pour Techron and HEET in gas tank.
- Press in schrader valve to release any pressure.
- Unscrew valve. id use a length of hose and shove it over the threaded part to direct gas in a container.
- Turn key to "on". Fuel pump should kick on.
- Drain as much gas as you want.
- Put valve back and start the car.

When putting the Techron in id try and mix it up with the gas. If you had a container with another gallon of gas put the Techron in then pour the container of gas in. Or can try bouncing the rear end of the car to get the gas mixed up.

Ignore the part about the fuel pump relay below.

JettaRed

iTrader: (1)

Maybe you missed my post above with attachments on how to drain the fuel tank and relieve the pressure in the fuel rail. The procedures are out of the WIS. There is a specific part that is used. It's ONLY $157.

Odd Piggy

That’s the right way to do it, but I’m still not a fan of recommending it to everyone.

TimC300

Reading that procedure just hook up the hose and the gas starts flowing out. Can probably use a hose from a cheap fuel pressure testing kit like the ones sold at HF. When I look up the Mercedes 119589046300 hose it looks like its been around for years.




Im not sure what exact fitting it is, but I came across a write-up and it says the Actron CP7818 Fuel tester works for most Mercedes with the schrader valves. When I read the reviews for that tester people say it also works on Ford F150, BMW E46, Chevy, even harley.









The point im trying to get at is if you need to work on the fuel rail you may not need that expensive Mercedes 119 hose. A cheap Amazon or HF hose should work. Just have to find the right one.

Also in my searching around I came across people saying this schrader valve worked if someone needs to replace it.

Koolkozak

Thank for your help everyone. I poured in half bottle of Techron Fuel System Cleaner and 1/4 bottle of the the yellow color HEET, bounced on the trunk a few times to let it swirl around. Started the car up after 5 minutes of sitting…. Car stopped misfiring and cleared up so I reset the CEL codes and then drove the car about 40 miles. The CEL stayed off but we will see.

tires were bumping a bit from the rot and rubber being disfigured but then cleared up after a bit of highway driving.

i do have a whining noise from the engine bay. Gets whinier and higher pitched as I accelerate more. Only in the first 3 gears. But then it’s still there when I put it in neutral or park and rev the engine.
im thinking it’s just the serpentine belt? Didn’t see any cracks in the belt.