I've been fighting a misfire problem for a couple of weeks and wondered if anyone had anything similar happen to them.

It started when I increased the size of the meth/water nozzle. I went from one rated at 7 GPH, which wasn't controlling the IAT to a 15 GPH. The funny thing is that I'm getting 90% or more of my misfires from cyl #6 with a few on cyl #2 (the next one in the firing order)

SMC is sending me a 10 GPH nozzle to see if that helps. If it doesn't fix it he wants to go to a dual nozzle setup with smaller jets, either 2 * 5GPH or 2 * 7GPH.

I'm thinking that there is a atomization problem at that volume and I'm having liquid flow into the intake and ultimately into that one cylinder.

Just to be sure that it's not a simple issue I have swapped the plug, wire, and coil from cyl #4 to #6 but the misfire still occurred on #6.

Anyone have any input?

TIA

 

What is your meth/water ratio? If it's 50/50, try 80/20 meth/water. Water doesn't combust. I've always wondered how much flow can be seen with a 50/50 mix until there is too much water going in.

 

I was running 50/50. I went to 65/35 to see if that helped any. No change.

I even bought a hydrometer to take the guess work out of mixing it.

 

If its meth related I would think you could drive around out of boost (not spraying) and log misfires. No misfires would indicate it is a boost/meth probelm?

 

I've done that. There are no misfires until it gets under boost (the methanol spraying). If I disconnect the meth injection the IAT's go through the roof but I don't get misfires. It has to be the alky/water mix but I just don't understand why it's limited to only one cylinder.

I'm assuming that the few misfires that are showing up on #2 are related to the fact that it's next in the firing order after #6. Does that make since?

 

I'd have to agree with your thoughts. Liquid flow or more getting dumped to #6. Pull the nozzle and spray it see if its misting real well. Might try different placement of the nozzle if the lesser size doesn't work.

 

...Ever try indexing the plug in #6 away from the intake charge? Just throwing out some quick ideas

 

No, that thought hadn't crossed my mind. Interesting.



The meth system is disassembled and waiting for the new nozzle.

I have come up with a way to test the controller. I have to pick up a few pieces tomorrow but I'll be using a radiator pressure tester to supply simulated boost into the controller and my boost gauge to measure the amount of pressure being applied. The meth controller is tee'd off of the boost gauge, so I'll just apply the pressure to the boost gauge tube. It'll take 2 people, one to watch the gauge and controller in the truck and one to watch the spray nozzle but it should work.


Where there's a will there's a way.


I just hope it helps the problem

 

I just read this. Interesting problem. Meth causing one cylinder misfire. Hmmm.

You don't have anything special going on with #6 do ya? How about your rpm reference? where are you getting that? coil or white wire off the pcm? how about your meth leaking? line running by #6 coil pack and a small mist hitting your coil? Just thoughts as well. Definitely keep us updated on this one, gotta say, I wouldn't know what to do with that one. Cam?

 

Nothing special about #6. The stainless meth line is not close to that cyl.

As far as the rpm that it occures at, it's not rpm specific. I can take off at WOT and It'll pull through low gear just fine to the shift point, 5800rpm. Sometimes, it will start to log misfires at the very top end of first gear, other times if won't start untill it's in second gear, just after the shift and around 3800rpm. It seems to be more related to the length of time that the meth has been spraying than the rpm. It won't misfire untill the meth has been spraying for a couple of seconds and then it starts racking them up quick. Once the log starts showing misfires, it doesn't stop untill a couple of seconds after I get out of it.

The cam and valvetrain are stock with 63k on them. I think that they are fine, since it doesn't miss if I disable the meth.

Hopefully I'll get the new 10 GPH nozzle today and get it in tonight.