hey everyone i have some multiple cycl missfires going on. they were sporatic every blue moon with usually only the no 5, or 3, or 6 however since i installed these shorty headers now i'm getting damn near every one on passenger side of engine and the no. 3 on drivers side. i do hear a slight exhaust leak on drivers side however theres a couple of those header bolts thats hard to get to because they are in the curve of the header and you can't get a socket or the "box" end of a wrench on it only the open end. They are 10mm bolts. I did let the fuel get really low prior to this. Now to cut to the chase evrything ignition wise is brand new, TB sensors are new, and I cleaned the injectors and fuel rail about 3 months ago. Anything else????????

 

Are the spark plug wires routed properly? Improperly routed plug wires can cause misfires and/or crossfires.

Have you checked your catalytic converter recently? A plugged one of those will also cause misfires. Have you noticed a loss of power as well?

Those are two ideas off the top of my head. More guys here will post more.

 

Maybe you just picked up some moisture or some debris by running the tank low. I assume you know to check the cat and plenum. And have the SP wires run according to the TSB.

 

hwy Jase and Zman, yeah I have the wires routed correctly and the cat was just check about 2 wks ago and only had 1lb of pressure ( per muffler guy whatever that meant??? )
Is there a correct way to clean out the fuel tank so this does'nt happen. This is so freaking frustrating. Before I ued to battle the no 5 missfire then that's fine now every once in awhile the no 6 and 3 would act stupid. now it's a bunch of them. This weekend I did the TB mod of shaving down the "lips" around the air induction holes and took the time to fully clean the TB. The plenum was done last year upper and lower(plate).

 

you routed them after the install?

 

yes sir. is this a bad thing?

 

You should remove the tank and clean and inspect, at least siphon the tank out and see what you got. Then do a complete flush of the fuel system. And btw have you checked your fuel pressure lately?

 

Yes Zman the fuel pump assy is less than a yr old. The last time this happened I over dosed every tank full with Seafoam and after about the 3rd tank and upgrading to the middle grade of gas everything was ok. This is what prompted me to remove the fuelrail, and injectors and clean them. I replaced all 8 "O" ring gaskets and then reinstalled then system.

 

The cam and/or crank sensors can also cause this. As far as the fuel system goes, got enemies! BTW, I would still check the fuel pressure.

 

OK I'm glad up brought up these sensors (Crank and Cam) I've asked this before as to where they are located and didn't get a clear answer. My rig has 145K miles on it 90% highway miles and I keep the maintenance on it up religiously. No enemies that I know of unless some of the Syrian Army soldiers remember me from 1984-85 during the Beruit conflict.