Carbon Buildup/Cylinder Misfire
 

On start-up, after about 30 seconds of smooth running, the engine would start to rattle and make a really horrible clanking/grinding noise. The hybrid system does not come on nearly as much as it should anymore. The check engine light comes on for a day or 2, then goes away, but comes back within a week (issue has been going on for 4 weeks now). Took it to Nissan dealership and they hooked up a diagnostic to it. It showed cylinder 3 was misfiring. After letting them do further tests, they came back and said I would need a "Top End Engine Decarb", for which they want to charge me $372 which is not covered even by my extended 6 year warranty! I told them that this issue seems to be known by Nissan (from reading posts about other people's experience with this issue and the techs that checked it) and was worried the cylinder head might be damaged from the carbon buildup and paying all that money for a top end decarb and then finding out the part needs to be replaced anyway would not be ideal.

Anyone have advice on how to deal with this? Is it possible to convince the dealership that this should be done under warranty? Is the cost for them to run some chemicals through the engine really $372? I live in Northern NJ, so if anyone knows a dealership that will take care of this in a better way, please let me know!

Re: Carbon Buildup/Cylinder Misfire
 

You can get this done at any good shop that uses a BG system, and probably for a LOT less money.

Go to www.BGfindashop.com and type in your ZIP code to find a shop that uses BG products.

Ironically, your Nissan dealer is probably using a BG machine and chemicals to do this service; they just charge too much money for it.

You could also need something other than a carbon cleaning service. If you are getting a check engine light, you could have a bad plug, bad coil or sensor, or other problems.

Good luck!

Joe

Re: Carbon Buildup/Cylinder Misfire
 

Thanks Joe. I checked out that website and called one of the service centers. The guy I talked to was shocked that I would have such devastating carbon buildup with less than 22K miles on the car. He said the maximum cost to flush the top end of the engine would be $250. He also recommended I try to call other Nissan dealerships first and Nissan Corporate since I am still under warranty (extended 6 year, car is 2 years old).

I looked at service bulletin NTB10-056a and it matches my issue exactly, however it appears that the dealership didn't follow this flowchart. When they came back with a confirmed diagnosis of carbon build-up, it was like stating the obvious. The service girl said they did not take anything apart to check for cylinder damage or valve issues like the flow chart says to do, so I feel like they just want to overcharge me for a top end de-carb.

Re: Carbon Buildup/Cylinder Misfire
 

Yes, I didn't realize you only have 22K on your car. The shop is right; there is virtually NO WAY you can have that much carbon buildup without a major component malfunction.

If you do have enough carbon buildup to interfere with the way the car runs at only 22K miles, I would suspect a stuck or dirty fuel injector. Either way, replacing that one injector and cleaning the cylinder should have it running like new.

Joe

Re: Carbon Buildup/Cylinder Misfire
 

print out the flow chart and go back to the stealership. if you don't feel like dealing with them anymore, try a different one

Re: Carbon Buildup/Cylinder Misfire
 

Update:

The 2nd Nissan I went to just called and told me the head needs to be replaced and it is under warranty since it is on a tech support bulletin. It will take about 3 days to get the part and do the work. I knew that all this should be under warranty, so I'm glad I didn't let the first dealership rip me off.

Re: Carbon Buildup/Cylinder Misfire
 

Here's another update:

The dealership called me and said the cylinder head is on back-order because this issue is now becoming more widespread. I'm number 28 on the wait list for a head and it might take 1-2 weeks to get it in. Maybe Nissan will issue a recall someday, but for now bulletin NTB10-56a covers these issues and the warranty should take care of everything. I don't know a lot about cars, but I think the cylinder head is the large block that covers the cylinders and contains the valves and springs, which means a newly manufactured head might take care of the carbon buildup issue.

Re: Carbon Buildup/Cylinder Misfire
 

JoJo,

Glad you found a competent dealer! Sadly, if you had been ripped off for the $372 and yet had a bad cylinder head, the cleaning would NOT have fixed the problem.

Replacing a cylinder head on a car with 22K miles is a BIG deal. Heads get replaced because they crack, warp, loose one or more valve seals, valve seats or the camshaft(s) go bad. The head on your car would never be repalced for excess carbon buildup.

This however, speaks VERY poorly of the first dealer that got it wrong. I would never go there for any other service, but I would call (and enjoy) telling the owner or general manager of the dealership that he has Moe, Larry and Curly running his service department, and they are running customers off to other Nissan dealers.

BTW, is Nissan providing you a loaner car while you wait for the car to come in? I would insist they do so; three weeks for a part is not reasonable or acceptable.

Good luck!
Joe

Re: Carbon Buildup/Cylinder Misfire
 

I think you are right about the head not being replaced just because of the carbon. It's probably at the very least because the valve springs are not strong enough to break up the carbon and maybe a newly manufactured head will be better able to handle the constant start/stop of the engine.

They put the car back together for me and I took it home so I didn't have to leave it there. I don't think this place had loaner cars (they had shuttle service). They said it will take one day to replace the part once it's in. They also told me that in addition to the engine code for cylinder 3 misfire, there was also a transmission code which they think will be fixed by replacing the head.

I'd like to tell the first dealer about this because the exact concern that I expressed to them about flushing carbon from a part that is ultimately defective/broken is a waste of money wound up coming true. I guess even though Nissan pays the dealer for warranty work, they could get more by charging me a ton for cleaning and claiming it's maintenance and then having me come back to do the actual warranty work.

Re: Carbon Buildup/Cylinder Misfire
 

Last update (unless the problem comes back):

I just got my car back tonight after having the head replaced. When I started it at the dealership after it had been sitting outside for over 24 hours, it ran smoothly. During the part where it would normally rattle badly, it transitioned smoothly. This is only 1 night, so we will see how it acts in the coming weeks.

*Also wanted to add that in addition to the cylinder misfire code, they found a transmission code, but that went away after the new head was installed.