diagnosing misfire w forscan

[withku]

So I’m having some idle issues since I installed a UPR Dual Valve Catch can. Rough idle, with misfires on cyl 5 and i’ve seen a few on cyl 3. Only at idle, so I grabbed some forscan videos. It seems Im either running rich or lean , but which is it? I have swapped spark plugs and coils but no luck. Data logs are below. thoughts?

https://imgur.com/a/IxEwYkJ

 

[SHOrod]

Are you getting P0303 and P0305 diagnostic codes, or just basing your misfires on the cylinder acceleration numbers shown in your video? Does Forscan have the ability to display actual cylinder misfire counts?

With your short term fuel trims showing negative values, that would suggest the car thinks it's running rich, so it shortens the fuel injector duty cycle (negative fuel trim) in an attempt to lean things out. Since the spark plugs are pretty easy to access on this engine, I'd start by swapping the spark plugs between cylinders and the coils between different cylinders, then see if the misfires follow either the plug, the coil, or remain the same.

-Rod

 

[withku]

Are you getting P0303 and P0305 diagnostic codes, or just basing your misfires on the cylinder acceleration numbers shown in your video? Does Forscan have the ability to display actual cylinder misfire counts?

With your short term fuel trims showing negative values, that would suggest the car thinks it's running rich, so it shortens the fuel injector duty cycle (negative fuel trim) in an attempt to lean things out. Since the spark plugs are pretty easy to access on this engine, I'd start by swapping the spark plugs between cylinders and the coils between different cylinders, then see if the misfires follow either the plug, the coil, or remain the same.

-Rod

Well I’m not getting any codes, but ForScan has a misfire monitor. I have swapped plugs and could, no change. As it’s mainly a single cyl misfire it seems only compression or an injector is the fault here but symptoms don’t match.

 

[76FoMoCo]

swap the injectors just as you would plugs and see if it fallows.

 

[Ta2dResqr]

I agree with @76FoMoCo. Swap your injector (and/or have them cleaned and balanced). This will isolate the cylinder. You swapped ignition (coil and plug). Now you swap fuel. If the problem stays, then the only thing left is the mechanical cylinder. You can then do a compression test and a leak down test. You may be chasing nothing since it is not throwing a code. How many misfires are you showing on your counter?

 

[withku]

I agree with @76FoMoCo. Swap your injector (and/or have them cleaned and balanced). This will isolate the cylinder. You swapped ignition (coil and plug). Now you swap fuel. If the problem stays, then the only thing left is the mechanical cylinder. You can then do a compression test and a leak down test. You may be chasing nothing since it is not throwing a code. How many misfires are you showing on your counter?

I actually did a compression test, 75 psi on cyl 5, 190 on cyl 6. Wet test didn’t change anything, so i’m moving to valves now.

 

[Ta2dResqr]

I actually did a compression test, 75 psi on cyl 5, 190 on cyl 6. Wet test didn’t change anything, so i’m moving to valves now.

Doesn't sound good. Hope it is not to terrible.

 

[76FoMoCo]

Sad

 

[withku]

Doesn't sound good. Hope it is not to terrible.

So I scoped my intake valves, and they’re covered in gunk. Not sure if a valve isn’t seating correctly or what it is. Sprayed some CRC intake valve cleaner on there but it didn’t do anything.

 

[Ta2dResqr]

Did you happen to scope the other valves? I personally have always had good luck with SeaFoam. I have not used it on a Turbo car though. I would need to do some research on the proper spot to induce a liquid to the system. I prefer the regular liquid can as opposed to the newer aerosol. I think the portion where you "flood" it to choke the motor and then let it soak probably does the most. This is where my biggest concern comes in with the turbos as you cannot compress a liquid. Short of getting the heads cleaned, I am sure you can research lots of methods people recommend for breaking up and cleaning deposits.

 

[withku]

Did you happen to scope the other valves? I personally have always had good luck with SeaFoam. I have not used it on a Turbo car though. I would need to do some research on the proper spot to induce a liquid to the system. I prefer the regular liquid can as opposed to the newer aerosol. I think the portion where you "flood" it to choke the motor and then let it soak probably does the most. This is where my biggest concern comes in with the turbos as you cannot compress a liquid. Short of getting the heads cleaned, I am sure you can research lots of methods people recommend for breaking up and cleaning deposits.

So I did a leak down test. 75% pressure loss… right out the oil fill and dipstick. Could it by chance be a head gasket instead of piston rings? or am i ******

 

[withku]

Sad

So I did a leak down test. 75% pressure loss… right out the oil fill and dipstick. Could it by chance be a head gasket instead of piston rings? or is she done

 

[76FoMoCo]

She's done. Head gasket will give you a coolant and oil problem. Ring is a vet to crank case problem. Valve is intake or exhaust leak

 

[withku]

She's done. Head gasket will give you a coolant and oil problem. Ring is a vet to crank case problem. Valve is intake or exhaust leak

dammit. don’t pistons typically go all at once? i’m at 85k miles and cyl 6 was 190 psi…

 

[76FoMoCo]

Piston is only a place to put rings. This is the point of sealing for compression.

 

[withku]

Piston is only a place to put rings. This is the point of sealing for compression.

Yeah I just figured if one went the rest wouldn’t be far behind. I redid a compression test, this time wet, and only gained ~10 psi. Not rings? or am i grasping at straws

 

[Shadow351]

Can you scope the cylinder through the spark plug hole? See what the piston and cylinder walls look like. Either way, looks like a major repair.

 

[RoketRdr]

Yeah I just figured if one went the rest wouldn’t be far behind. I redid a compression test, this time wet, and only gained ~10 psi. Not rings? or am i grasping at straws

You either have a cracked piston or broken ring/rings. Just because one cylinder is ****** doesn't mean the others are soon following.

 

[351Blueblood]

I bought my car with hurt #4 piston/rings that was giving the guy a misfire on that cylinder. This #4 hurt happens alot on these. Car was stock old guy like me driven. 123K 2010

 

[cali+Mocasho+]

Did you happen to scope the other valves? I personally have always had good luck with SeaFoam. I have not used it on a Turbo car though. I would need to do some research on the proper spot to induce a liquid to the system. I prefer the regular liquid can as opposed to the newer aerosol. I think the portion where you "flood" it to choke the motor and then let it soak probably does the most. This is where my biggest concern comes in with the turbos as you cannot compress a liquid. Short of getting the heads cleaned, I am sure you can research lots of methods people recommend for breaking up and cleaning deposits.

You ever figure out a good spot to seafoam?