welp, i just finished putting a new fastman tb on and an airgap fi intake. only problem is i lost my sct tuner i just bought last month, and now i have a backfire.... i hope it goes away after the computer relearns. waiting for an email back from hemifever, to see what i can do about a lost programmer..... sucks cuz i wanted to flash the tow tune, i have it on the economy right now.

 

Check the spark plug wire routing. You shouldn't have a backfire and time won't make it go away.

 

just barely replaced my plugs 3 to 6 months ago, but i had a cyl 8 plug that the tips were touching. replaced all of them and backfire went away. but i got a code for the map sensor, saying no change from start to run. and cyl 6 an 8 misfire. i cleared the codes, but it came back. will check in the mornin what codes its throwing now. the cap and rotor, wires and plugs are all new. what would be causing this? especially the map sensor? would any of the other sensors, cause a false reading on the map sensor not working? iat, tps, temp coolant sensor? iac? etc.

 

I like to do this. Any pictures of your set up?

 

First try unplugging the map sensor and test it (and it's power wire) with a multimeter going by the procedure in the Haynes manual.
If it checks out then clean the pigtail out with some contact cleaner and plug it back in. Clear the codes and see if they come back.
The map sensor has a little diaphragm in it that can stiffen up over time and it will make it not work correctly but I'm thinking it's a contact issue since it didn't do it before you swapped the throttle body.

I'm not sure what would cause the ground strap to close up on a spark plug aside from too much heat in that cylinder, someone else should chime in on that one.
Cylinder 8 misfire is normally caused by a plugged catalytic converter because it's the closest cylinder to it. When the exhaust valve opens on #8 all that pressure (burnt exhaust gasses) gets pushed back into the cylinder so there isn't a good mix of fresh air and fuel for the spark plug to burn.
The easy way to test the cat is to knock on it with a dead blow hammer or a rubber mallet to see if it rattles.
If it's plugged bad enough then you won't be able to red line the engine and the exhaust coming out of the pipe will be weak.

One other thing you can do is re-seat the spark plug wires for #6 and #8 and make sure you hear them click into place.

I hope you get it figured out but if you don't then there's plenty of people on here that know more than me and someone is sure to help you out.

 

lolll, wow. one thing after another. cleared the codes this mornin, no more misfire codes and the map sensor checked out. the only thing left is a p0331, knock sensor it says. its the only code that continues to pop back up after clearing it. i checked the ohm reading on the injectors, theyre fine. the only thing i can think of is to bump up to bigger injectors, but i dont think i need them.

 

Erm.... I didn't think our engines even HAD knock sensors???? WTF?

 

exactly my point, there shouldnt be a knock sensor. but thats the code the computer keeps telling me.

 

What were your voltage readings on the map sensor how did it check out? What were the ohms on the injectors? ID like to see some pic's too. The phantom pinched wire.

 

they were 12 on the injectors. map, sensor i dont remember, but it was fine. what exactly do you guys want pics of? and ill snap some of specific parts, or just everything.