DROPTOPLS1

iTrader: (28)

I am trying to start my new 408 and when it is about to start it backfires big. My coil packs are from a 98. Is there any way I could have hooked them up wrong when I put them on the brackets. Anyone have any ideas ?

ALLBOTTLE

iTrader: (13)

did you install the cam?

Single or double roller?

chromeplated500

iTrader: (10)

Check the timing....quick double check that the dots are lined up... doesnt hurt to check..

g-ryde1

iTrader: (3)

def, had a car do this turned out the guy i was working with knew nothing about installing a cam and put the cam in wrong. broke pushrods, bent valves and cracked the heads something good to check on before it becomes expensive bro

trans_am_31

iTrader: (51)

Hey listen, Yes it is very possible that you may have put the wrong plugs on your coils. Check them, I did the same mistake once and learned from it. Otherwise check the timing, that the dots are line up in the cam. Hoepfully its something easy. Let us know how it turns up. Good Luck!!!!

DROPTOPLS1

iTrader: (28)

I installed the cam and double roller, it was definitaly dot to dot. I checked piston to valve clearance. I am going to try a friends coilpacks and if that does not work I think it is the timing. My friend came over with his hp tuners the night I was finishing up but had to leave before I was done. Maybe something is off in the tune. I will let everyone know what happens.

nikon1999

iTrader: (22)

even if timing is off in a tune it shouldn't back fire really, never seen that... I'd check to make sure you have the coils plugged in properly

DROPTOPLS1

iTrader: (28)

I dumped the oil because it smelled a little like fuel and put in new oil. I then put my brothers coil packs on from his 5.3 truck and pulled the fuse for the fuel pump. There was so much fuel in there from trying to start it yesterday that it fired right up. When I put the fuse back in I got it to run for about two minutes before it stalled and I could not get it started again. The gauges started getting all funny when you turned on the ignition. I now have to figure out how to wire my coil packs and get my friend over with his laptop. It did sound good when it started with 12.1 compression and a big cam.

White_Hawk

iTrader: (3)

Does it run at all? Did you do a crank re-learn?

-Geoff

DROPTOPLS1

iTrader: (28)

Yes it ran for a couple minutes. What is a crank re- learn?

White_Hawk

iTrader: (3)

It is a diagnostic/calibration procedure built into a Tech 2. Sometimes the PCM has to re-learn the crank signal. It can cause issues like you're having. If you are stumped, and you can find one, it is definitely worth a try.

-Geoff

Daniel_z28

iTrader: (9)

also check the camshaft position sensor, a bad camshaft sensor could thow off your timing casuing the backfire issue. when my crankshaft position sensor went out, it would still start and run after clearing the codes but ran rough at higher rpm until I did the crankshaft re-learn.

XREDxTAx

mine didi the some thing ( the back fire on start up) i had the harness plugged in to the coils backwards. damn the simple things!

ChucksZ06

iTrader: (9)

Make sure your crank position sensor is plugged in and the wires have continuity.

DROPTOPLS1

iTrader: (28)

I fixed the problem, the coil packs were plugged in wrong on the passenger side.