Headers went in relatively easy. Installed by myself on jack stands. No simms or tune yet. After I got everything buttoned up I went for a test drive. Ran great for about 5 or 6 miles then it started misfiring, P0300, P0171, P1133 and P1153. I was hoping to be able to drive it to Dallas (300 miles) for a cam install and dynotune next week. I do have a predator and can add some fuel for the lean condition in bank 1 (P0171) but will it be enough? Perhaps I should put the factory tune back in and see if the misfire and lean fuel trim get corrected. Any other ideas???

 

Restore stock tune
check your plug wires.
she how she runs.

 

Also make sure you didnt accidently bump any connectors loose on the wiring harness.

Shane

 

Didn't get to do much today but I did recheck and reseat all electrical connections and hoses. Pulled all plugs and plug wires. Wires look okay. Passenger side plugs are great, no fouling or sooty plugs. All for of the driver side plugs are completely sooted. Cleared codes and restarted, still running rough and get P0300 with a flashing CEL. I listened for an air/vacuum leak but I couldn't really tell as it sounds completely different with the headers. My set did not come with headers gaskets so I reused the OEM metal gaskets. I did notice two spots just above the header flange that has a small amount of soot protuding out. Could this be a leak big enough to cause the P0300? Tomorrow I will reinstall the OEM plug wires and change plugs. Any thing else I might have missed or need to check???

 

check the gap on the plugs to make sure they are all correct. possibility you have a bad wire.

 

Make sure you didn't cross the front 02 sensor wiring.

Left sensor > left harness. Right sensor > right side harness.

Crossing the connections is a common error people tend to make when installing LG headers, and doing so will produce all of the symptoms and codes you're seeing.

 

and for added confusion. the rear O2 sensors are SUPPOSED to be crossed at least i think they are if i remember correctly.

Shane

 

I have the rear O2 Sensors moved to the front bungs in the collector. They are connected left sensor to left side and right sensor to right side. I have the rear bungs in the X pipe capped with 18mm X1/5 pitch oil plugs, they both nhave a good tight seal. I will be reinstalling another new set of plugs and replacing the Taylor 8mm plug wires with OEM plug wires today. What I don't understand is why all 4 cylinders on the drivers side only are misfiring, black sooty plugs? Another question I have is when the P0300 random misfire is corrected will it be immediate or does the computer need to cycle thru to correct the changes?

 

either you have a air/vacuum leak on bank 1[will be loud enough to hear],header is loose or leaking[o2 seeing too much air]or another possibility is a loose o2 sensor.if all is ok,swap the front o2 sensors from side to side,if bank 2 is now lean,you have a bad o2.

 

I swapped them yesterday just out of curiosity and the symptom stayed with bank 1, driver side. I will loosen up header today and retighten along with changing the plugs and wires.

 

look for a vacuum/air leak.also check for air being sucked through the secondary air base

 

This really sounds like the O2 sensors. That is exactly the condition I had after doing my LG's and it was that I had the sensors crossed.

 

,but he claims they are not crossed.

 

They are not crossed. After reading thru the treads search that was what i thought as well but mine are connected correctly, right sensor to right harness and left sensor to left harness. When I swapped sides with the sensors the problem stayed with bank 1. I am leaving work early, at 10:00 am, to install a new gasket on bank 1, driver side along with new plugs and OEM wires. When I get back to a computer I'll give an update. Thanks!

 

i was half asleep this morning when i posted and went brain dead.did you check the o2 fuse[1133/53 are insufficent switching]?

 

 

Well, I removed the driver side header and replaced the gasket. Also replaced the plugs and plug wires on the driver side only. Again checked to be sure the right side O2 sensor was connected to the driver side harness and passenger side O2 sensor was connected to the passenger side wiring harness. All looked good . Started her up and she idled smooth as silk. Realigned the exhaust tips and took it off the jack stands. Started up the engine and again, smooth. Headed out for the test drive and everything was fine for about a mile or two, Then she started cutting out/missing, flashing CEL and a P0300 code was set. The P0300 was the only code set. I pulled the first two plugs on each side and they were clean, no evidence of a misfire. Didn't have time to get the other four. I started it back up after about a fifteen minutes all was fine for a little while then the misfire reoccured. I did that two more times, she would idle fine for a few minutes then the misfire would start. Wouldn't get a CEL while idling but when I would run to about 2500 to 3000 RPMs it would set. I didn't know about the fuse for the O2 sensor but I'll check that tomorrow as well as checking the other plugs for evidence of a misfire. I am really begining to suspect a bad O2 sensor but if the code is just P0300 how do I determine which one might be the culprit?

 

if it's misfiring under a load only,you most likely have a ignition issue,either a plug that's cracked,a plug wire not "locked on",something like that.not a 02 issue.unless you are really fat[rich] or light[lean],but you would have faults.recheck the plug wires and make sure you "feel" them "click" on,also make sure they are not burning on to any of the header tubes.

 

Okay, I didn't change the plug wires on the passenger side so tomorrow I'll pull off the Taylor wires and reinstall the OEM wires. I really do appreciate your input, along with everyone else. Hopefully I can get it rectified tomorrow.

 

Don't know about now that you've replaced the header gasket, but for sure the soot near the joint was the clue. Even a small leak can suck in air and trick the computer into thinking the bank is lean, so it dials in unneeded fuel and runs rich, causing misfires, melted cats, etc...