[SRT-Bill]

Okay, I had new heads, underdrive pulley and 85MM TB installed. Car ran good for about 5 miles then the CEL came on and car started running rough. Code P0300, random misfire. It actually sounded like it had an exhaust leak. Figured that I couldn't do much about the heads or UD pulley so I put the Factory TB back on and cleared the code. The car ran fine until today(about 2 weeks). This is the first time I went WOT and it came back on and
started flashing. When I stopped the car it stalled. It fired right back up but I am guessing something ain't quite right. Any ideas? Thanks, Bill.

 

[PaCharger]

check the vacuum hoses.
check the connector on the back of the intake manifold


no odd lifter noise or high fuel burn right?

 

[SRT-Bill]

Cel

While the CEL was on my mileage dropped from 14.8 to 12.6.

 

[PaCharger]

sounds like a push rod not seated on a lifter. when you tq'd the rockershaft down did you turn the motor over by hand and see EACH spring get compressed?

If not....go pop the valve covers and start there.

 

[SRT-Bill]

I had it done at a shop. Head install is out of my realm of capabilities.

 

[Hemi31]

you need the valve covers off........see if there is a specific cylinder with the p0300.......like p030x.....the x will be a 1 through 8.......that will tell you which cylinder it is exactly.

 

[SRT-Bill]

The only code I have is p0300. How do I check for an individual cylinder? Thanks, Bill

 

[fnkychkn]

you'll need a starscan/starmobile to determine exactly which cylinders are misfiring.
any abnormal noises/backfiring under load?

 

[SRT-Bill]

No. I don't have any backfiring. The first time it did this was under WOT. I ran it for 2 weeks with what I thought was just an exhaust leak(no CEL). I then took it back to the shop and they couldn't find a leak. While it was there they installed an MSD timing controller for the NOS. When I picked it up I noticed the CEL was on but they said it was on the first time they started it. I figured it could have come on when I parked it. They cleared the code and when I left there it was running fine, the first cold morning I started it up it ran rough and the CEL came on. That is when I changed the TB and cleared the code. The rest is in post #1. When the CEL isn't on the car runs great. I drove it 200 miles to Orlando AFTER I cleared the code and changed the TB and my fuel mileage went from 12.6 up to 17.3 average. Bill

 

[fnkychkn]

could this be an EGR issue?
sorry, i don't know enough about NOS systems to be of much help on this one.
Hemi31 can probably steer you in a better direction.

 

[SRT-Bill]

Any other thoughts?

Bump!

 

[PaCharger]

No. I don't have any backfiring. The first time it did this was under WOT. I ran it for 2 weeks with what I thought was just an exhaust leak(no CEL). I then took it back to the shop and they couldn't find a leak. While it was there they installed an MSD timing controller for the NOS. When I picked it up I noticed the CEL was on but they said it was on the first time they started it. I figured it could have come on when I parked it. They cleared the code and when I left there it was running fine, the first cold morning I started it up it ran rough and the CEL came on. That is when I changed the TB and cleared the code. The rest is in post #1. When the CEL isn't on the car runs great. I drove it 200 miles to Orlando AFTER I cleared the code and changed the TB and my fuel mileage went from 12.6 up to 17.3 average. Bill

pull the valve covers and look for anything mechanical - bent push rod or bent rocker not seated correctly.

 

[Tbird100636]

could this be an EGR issue?
sorry, i don't know enough about NOS systems to be of much help on this one.
Hemi31 can probably steer you in a better direction.

No EGR on 6.1L.

 

[Hemi31]

the timing controller could have alot to do with it....I didn't think they worked on an LX.I would disconnect it.....if it still flashes you have a mechanical issue and the valvecovers need to come off.

 

[Tbird100636]

No. I don't have any backfiring. The first time it did this was under WOT. I ran it for 2 weeks with what I thought was just an exhaust leak(no CEL). I then took it back to the shop and they couldn't find a leak. While it was there they installed an MSD timing controller for the NOS. When I picked it up I noticed the CEL was on but they said it was on the first time they started it. I figured it could have come on when I parked it. They cleared the code and when I left there it was running fine, the first cold morning I started it up it ran rough and the CEL came on. That is when I changed the TB and cleared the code. The rest is in post #1. When the CEL isn't on the car runs great. I drove it 200 miles to Orlando AFTER I cleared the code and changed the TB and my fuel mileage went from 12.6 up to 17.3 average. Bill

Let me understand this right. After the heads there was what sounded like an Exhaust leak, then they installed the MSD Controller and the MIL started coming on??? For one, the MSD controller must not be working right, causing a multiple cylinde misfire. For the noise, put the trans. in drive, hold the brake and give the engine some throttle. Have someone listening for leaks.

 

[hemi nick]

Okay, I had new heads, underdrive pulley and 85MM TB installed. Car ran good for about 5 miles then the CEL came on and car started running rough. Code P0300, random misfire. It actually sounded like it had an exhaust leak. Figured that I couldn't do much about the heads or UD pulley so I put the Factory TB back on and cleared the code. The car ran fine until today(about 2 weeks). This is the first time I went WOT and it came back on and
started flashing. When I stopped the car it stalled. It fired right back up but I am guessing something ain't quite right. Any ideas? Thanks, Bill.

any one of those changes can cause a po300......with all those new mods im sure you have a new tune, what does your tuner think?

 

[hemi nick]

SRT Bill, does your car sound like it has an exhaust all the time , or only when your code is showing?

 

[SRT-Bill]

I got her to the shop and they called me today. It is a fault code for the fuel pump module. I talked to Fixer and he said the early 06 cars had a fuel pump sensor that was prone to failure. Any ideas about this? Thank you everyone for all the replies, Bill

 

[fnkychkn]

I got her to the shop and they called me today. It is a fault code for the fuel pump module. I talked to Fixer and he said the early 06 cars had a fuel pump sensor that was prone to failure. Any ideas about this? Thank you everyone for all the replies, Bill

??? never heard of a fuel pump sensor. the only monitored fuel pump circuit is the relay control.

 

[SRT-Bill]

So can the fuel pump relay be what is causing the problem?