Cylinder 10 misfire code.... help

[GTSnake]

I keep getting the cylinder 10 misfire code P0310. It only comes on intermittently. Since May it's come on 3 times. Each time I tried to change something, erase the code and it comes back. I've tried switching wires between #8 and #10, switched plugs with #8, insulated the wires with heat wrap but it still throws the Cyl#10 misfire code. Here are my mods:

1) 10lb Roe with latest VEC2 firmware
2) Magnecore wires only 2 yrs old
3) ported Roe manifold
4) Jeff Morys Striker heads with 4 step colder Iridium plugs.
5) 70mm TB's
6) Belanger Headers
7) Random high flow cats
8) New O2 upstream sensors

The car seems to run ok with a slight hesitation around 1800rpm under moderate load. Joe Donovan tuned out most of the hesitation but there's still a little bit left. Don't know if it's related or not.

My mechanic thinks it may be nothing. Since the car is heavily modified he says the PCM may be sensing something that really isn't there.

Anyone have any ideas? I'm fresh out.

 

[FE 065]

Found this on the subject of misfire codes


The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause.

Possible Causes:

Ignition system
Fuel injectors
Running out of fuel
EVAP canister purge valve
Fuel pressure
Evaporative emission system

 

[plumcrazy]

didnt jackB have a fix for this at one time?

 

[GTSnake]

So what if the VEC2 injector offset was set too lean. Would that cause a misfire? I'll try to even it out with the rest of the cylinders and see what happens.

 

[Doug Supercharged Vipers]

Be as it may - if we determine everything to be ok on a highly modified car, we remove the misfire detection from the PCM.

Best of Luck,
Doug

 

[GR8_ASP]

I had very BAD luck with iridium plugs. What brand and what gap did you set them at?

Note I lost 150 RWHP with them, all seemingly due to high speed miss as the torque loss started around 4000 rpm. Switched plugs with no other changes and the hp came back. From what I gathered the iridium plugs may require higher energy than the stock ignition system can provide with the gap I used, thus the loss at higher engine speeds.

 

[GTSnake]

Be as it may - if we determine everything to be ok on a highly modified car, we remove the misfire detection from the PCM.

Best of Luck,
Doug

Doug, what would be the downside be if I disabled the misfire diagnostics?

What brand and what gap did you set them at?

Ron, They were the plugs that Jeff Morys gave me with the heads. I'll try a set of champion plugs.

 

[Schulmann]

GTSSnake,

If you are using 4 step colder irridium plugs, maybe that one is causing the misfire. Can you post a picture about your plug at cylinder #10 ? I am sure it is black and the plug can`t perfectly ignite under boost.

For street and moderate racing try to use warmer plugs: Something like NKG FR5. A 4 times colder plug is good for extended racing.

Also set the fuel offset to -1ms at cylinder #10. It might help a lot.

Install also two WBO sensor kit in each exhaust. It could help you to easily diagnose similar issues. With a 10lb pulley I would even say it is a must.

 

[FE 065]

So what if the VEC2 injector offset was set too lean. Would that cause a misfire? I'll try to even it out with the rest of the cylinders and see what happens.

What if it's just #10 injector causing the problem ?

 

[plumcrazy]

a 4 step colder plug sounds extreme

 

[GTSnake]

If it's the plug then how come none of the other cylinders show any problem? Then again maybe it's a combination of the injector offset and the cold plugs.

The reason why we chose the 4 steps colder was to avoid any detonation. I'll change the offset first then change the plugs up two steps warmer.

 

[Schulmann]

What is the plug number ?

Anyhow, at cylinder #10 there is less air thus the AFR is lower if not adjusted with the offset in the VEC2. My offset for highway is -1.50ms and for city -0.9 ms !

Now if you combine a cold plug with a low AFR (something like 11-12 at vacuum) you end up with a fouled plug and ignition issues.

I use NGK FR5 in all cylinders except 10 where I use FR5-1.

 

[KenH]

Seems like the first step would be to pull the #10 plug and see if it looks like it is running rich or lean and then adjust the VEC2 injector offset accordingly on that cylinder. #10 usually runs too rich with the Roe SC and it is the first cylinder to have fouling problems. The very cold plugs that you are running could be contributing to the problem as well.

Doug, I am curious about your comments as well. Are you saying that heavily modified engines tend to get a little cylinder misfire which you may need to learn to live with, or is the PCM just picking up false misfires from the changes to the engine? I used to get an occasional misfire code with my '01 PCM, but those went away when I switched to a '96 PCM.

 

[GTSnake]

What is the plug number ?

Anyhow, at cylinder #10 there is less air thus the AFR is lower if not adjusted with the offset in the VEC2. My offset for highway is -1.50ms and for city -0.9 ms !

Now if you combine a cold plug with a low AFR (something like 11-12 at vacuum) you end up with a fouled plug and ignition issues.

I use NGK FR5 in all cylinders except 10 where I use FR5-1.

I can't remember the plug number. I'll have to pull it later. It's a funky type of plug that has a 1" reach due to the Striker heads. My plugs were very clean when I pulled them a few weeks ago. They were not fouled at all. However I had the offset at -2.2ms for #10 cylinder. As stated earlier I have the updated firmware as well as a ported manifold that should help with the #10 rich ratio.

 

[Schulmann]

-2.2ms is another extreme setting.
You definitely need two WBO kit for each exhaust side.
You will see how much it is easier to tune your viper with them.

Check the LC-1 from Innovate.
They are easy to connect to the VEC2.

I will try to describe your situation:
You are like a pilote who tries to land his aicraft on regular basis in the night with lights turned off at the airport. It is feasable once but it is a matter of time before he hits the ground very strong.

So spend the $400 for the two LC1 and you will see what you always wanted to see: your AFR ... espectially with a 10lb pulley you need to have a good idea about your AFR.

Once you stabilize your AFR you will be able to play with the ignition and this is where you will see huge changes in your torque.

 

[plumcrazy]

http://www.dynotunenitrous.com/store/scripts/prodView.asp?idproduct=150

 

[GTSnake]

The plug I'm using right now is the NGK Iridium LFR7AIX.

I also have a AF gauge connected to the O2 Sensors in the headers. Although it jumps around so much it's difficult to get a good reading on it.

When the car was tuned a few weeks ago by PBJ the AFR was a flat 12.5 with no detonation.

 

[Schulmann]

GTSSnake, you have a narrow band oxygen sensor. That one is not good for anything except for the stock PCM.