Engine Misfires - 2015 V8

[carguy75]

Definitely a good idea. I’ve got my mechanic scheduled next week to pull out my intake valves and chemically clean them. Sounds like he better check the plugs too while he is in there! Thanks!

You are welcome.

Hopefully new plugs and some concentrated fuel additive to clean your injectors will solve your misfiring issue as well as the valve cleaning.

 

[glennk]

Was there any brand mentioned of chemical used on the intake values?

 

[DSXMachina]

Definitely a good idea. I’ve got my mechanic scheduled next week to pull out my intake valves and chemically clean them. Sounds like he better check the plugs too while he is in there! Thanks!

Your mechanic is going to pull out your intake valves and clean them? Be prepared for a bill over $2000. I think you have a communication problem. Your mechanic is NOT going to remove your intake valves. That is a lengthy (about 20 hours labor) and expensive procedure which is entirely unnecessary. Removing sparkplugs is fast and cheap. Think two hours if he stops and reads a trade magazine in the middle of the job.
I agree totally with carguy that a proper diagnosis needs to be made and step one is to remove and "read" the sparkplugs. An experienced tech can learn a lot about the health of each cylinder by examining the plugs.

 

[DSXMachina]

Was there any brand mentioned of chemical used on the intake values?

Yeah I'd like to know the same thing. Been cleaning GDI's for years starting with BMWs a decade ago. Not a single liquid product has been shown to be effective. The only way you can get a solvent to do anything is to spray it directly onto the area and use a stiff wire brush to abrade the buildup. Even that doesn't give the best results.

 

[carguy75]

Yeah I'd like to know the same thing. Been cleaning GDI's for years starting with BMWs a decade ago. Not a single liquid product has been shown to be effective. The only way you can get a solvent to do anything is to spray it directly onto the area and use a stiff wire brush to abrade the buildup. Even that doesn't give the best results.

I will remove the intake manifold at 100k miles and manually clean my valve stems the best I can with some concentrated carbon cleaner, a wire brush, and a shop vac. The valves may not look 100% percent factory new, but it should remove most off the carbon of the valves.

 

[DSXMachina]

Given the v8 engine is so low milage , how could this be related to carbon builtup . Does it not built up slowly overtime . Most of GDI engines need cleaning at 70-100k miles .

Whats missing here . How can a engine misfire at 30 - 40 - 50 k miles ?

Again, I agree with carguy's approach to resolving the misfire. However to answer your question: 'Carbon buildup' is the result of hot/cold engine cycling, NOT mileage on the odo. Make a far above average number of short trips, or put on most of your mileage around town and you are going to get the buildup sooner on a calendar basis. That translates into having driven fewer miles.

 

[DSXMachina]

I will remove the intake manifold at 100k miles and manually clean my valve stems the best I can with some concentrated carbon cleaner, a wire brush, and a shop vac. The valves may not look 100% percent factory new, but it should remove most off the carbon of the valves.

You can buy cheap but good mini-cams on the web. Remove the intake snorkel and go in thru the throttle body while twirling the lead around. It's hit or miss but you can usually get into a few different ports to take a peek. While not certain, if you see those valves are good, chances are the others are as well.

 

[carguy75]

You can buy cheap but good mini-cams on the web. Remove the intake snorkel and go in thru the throttle body while twirling the lead around. It's hit or miss but you can usually get into a few different ports to take a peek. While not certain, if you see those valves are good, chances are the others are as well.

I have an insepction camera I use mainly on my chevy engine. I will take a look at the 5.0 pistons when I change my spark plugs soon in a few months to see if they are coated with carbon or not. If so, then I will be preparing to clean my valves stems for sure at 100k miles or sooner depending on how the combustion chambers looks.

 

[DSXMachina]

I have an insepction camera I use mainly on my chevy engine. I will take a look at the 5.0 pistons when I change my spark plugs soon in a few months to see if they are coated with carbon or not. If so, then I will be preparing to clean my valves stems for sure at 100k miles or sooner depending on how the combustion chambers looks.

I've tried my camera with the right angle attachment down the sparkplug holes. It is near impossible to see the backs of the intakes after making sure they are high on the cam lobes. I think it is possible to have clean piston tops, but still have fouled intakes. Of course if a cylinder misfires due to bad intakes then there will be more carbon buildup likely on the pistons. However, it seems a clean piston might not always mean a clean intake port/valve.
Regardless, if your pistons are clean and your engine is running good, then let's assume the best.

 

[V8freak]

Your mechanic is going to pull out your intake valves and clean them? Be prepared for a bill over $2000. I think you have a communication problem. Your mechanic is NOT going to remove your intake valves. That is a lengthy (about 20 hours labor) and expensive procedure which is entirely unnecessary. Removing sparkplugs is fast and cheap. Think two hours if he stops and reads a trade magazine in the middle of the job.
I agree totally with carguy that a proper diagnosis needs to be made and step one is to remove and "read" the sparkplugs. An experienced tech can learn a lot about the health of each cylinder by examining the plugs.

Uh... sounds like I need to talk to my mechanic again. Chances are i probably misunderstood him but I'll let ya know what chemical he uses.

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[carguy75]

I've tried my camera with the right angle attachment down the sparkplug holes. It is near impossible to see the backs of the intakes after making sure they are high on the cam lobes. I think it is possible to have clean piston tops, but still have fouled intakes. Of course if a cylinder misfires due to bad intakes then there will be more carbon buildup likely on the pistons. However, it seems a clean piston might not always mean a clean intake port/valve.
Regardless, if your pistons are clean and your engine is running good, then let's assume the best.

You hit it on the nose, clean pistons usually would indicate that my fuel injectors,spark plugs tips and piston rings are clean.

It seem that most owners on this forum are only concerned about the valve stems being contaminated with carbon, but forget that the fuel injectors, spark plug tips, and piston rings can be compromised by carbon build-up as well in a direct injection engine.

Hence why it is still important to use fuel with a good of detergent package or use fuel additives to clean the combustion chamber components clean even if the additives does nothing for cleaning the valve stems.

 

[V8freak]

Hey I just got my car back from the mechanic today. $400 later and clean intake valves this car is a world different! Runs smoothly and shifts great!!

 

[V8freak]

I forgot to get the name of the chemical from him but it’s a chemical that you soak the intake valves in and then use a brush and pick to clean them.

 

[V8freak]

Also not sure where the confusion is but he was shocked when you thought it would take 20 hours. He said it only took them maybe 3 1/2 to pull them and put them back in.

 

[DSXMachina]

Also not sure where the confusion is but he was shocked when you thought it would take 20 hours. He said it only took them maybe 3 1/2 to pull them and put them back in.

Hi V8. First let me congratulate you on the successful repair. Glad the valve cleaning took care of the problem.
As for removing the valves...he absolutely did not! Had he done that you would have paid over $400 just for parts (valve cover seals, head gaskets, assorted incidentals). Two of the worlds fastest mechanics working together could not remove and reinstall and clean the intake valves in 3 1/2 hours. Period.

 

[V8freak]

Hi V8. First let me congratulate you on the successful repair. Glad the valve cleaning took care of the problem.
As for removing the valves...he absolutely did not! Had he done that you would have paid over $400 just for parts (valve cover seals, head gaskets, assorted incidentals). Two of the worlds fastest mechanics working together could not remove and reinstall and clean the intake valves in 3 1/2 hours. Period.

Thanks! Lol I guess I can’t speak for him but he said he soaked them in the chemical overnight so that makes me think he had to have them out right? I guess I don’t really care anymore at this point, my car is fixed and it was cheap!!

 

[V8freak]

Also I should add that the 3 1/2 hours did not include cleaning them. Just to take it apart and reinstall them.

 

[CadiChaser]

Yeah sounds familiar! Mine was in the shop for a couple months! Im back to driving mine while my mechanic does more research. Let me know if that fixes it!

Injectors didn't fix the issue. Gdi induction service didnt work so they finally replaced the manifold converter and the car is driving better then ever.

 

[carguy75]

Thanks! Lol I guess I can’t speak for him but he said he soaked them in the chemical overnight so that makes me think he had to have them out right? I guess I don’t really care anymore at this point, my car is fixed and it was cheap!!

He probably just removed the intake manifold, soaked the valves with carbon cleaner, scrubbed the carbon off the valves and intake ports. That method would take about 3 hours. Either way, I am glad the cleaning worked out for you.

 

[V8freak]

Injectors didn't fix the issue. Gdi induction service didnt work so they finally replaced the manifold converter and the car is driving better then ever.

Ok gotcha! I thought mine was fixed but it still sounds a little rough at times and the check engine light also started flashing this morning when I put the excelerator on the boards. Shifts fine but obviously something is still a little bit wrong if the light is flashing. I might hafta ask my mechanic about that.