car backfiresunder heavy load.

[whtturbot]

I'm having a problem with the car backfiring under a heavy load. If i come to a stop and nail it the car boosts up and as it gets to the first second shift the car backfires thru the exaust. However if I gradually get on it from a roll and hit full throttle/full boost the car runs like a rocket. The boost is the same in both cases. Now Im thininking it may be the pump not keeping up, I changed it about 3-4 years ago, think it is a walboro, not sure though. The problem just started this year, Ive only had the car out 3 times this year. Any other ideas........... Im running 50 pound injectors, 48 psi fuel pressure line off, boost is set at 23


Jeff C
87 T
PTE 52
6.0 DFI

 

[441120]

fuel

If nothing has been changed, no new mods, are the coil & module O.K.?
How old is the fuel? you state only had it out three times, last years gas?
need the info

 

[TT/Ameasap]

Check the above mentioned and also check TV cable adjustment.

Turn boost down and work it back up if these check out. You might have the spark plugs gapped wrong for that amount of boost.

HTH
Bo

 

[alvin87gn]

backfires out the exhaust are nearly always ignition related. usually timing or plugs & wires.

 

[whtturbot]

The fuel was put in this year. The TV cable was adjusted using the full throttle method. I have the timing set low so I can run that boost level. Im going to change out the filter and pump this week. Hopefully the problem will go away.

Thanks for the advise, keep it coming.

Jeff C
87 T

 

[iamjeff]

i had a simular problem that was caused by a cracked #6 spark plug...oops. it would pull hard untilabout 12lbs and then backfire, fall on its face, and knock.

-jeff

 

[JP87GN]

I just got my motor back in my GN after doing Champion irons and CNC intake and have developed a backfire through the exhaust and a miss. Car seemed to run fine so I went to the track and the first run it backfired about 2/3 track and I ran a 12.4 @ 88mph because I got out of it. Check some things out and ran again with similar results. Then when driving it home I was doing about 60mph @ 1500rpm at it was studdering at missing like a ignition or spark problem. got home and changed the ignition and coil pack,ECM,swapped back to stock MAF meter and no TRANS +, and still does it. The pugs and wires are brand new. What are the chnces I have a bad plug right off the shelf?(NGK UR5's) What are my other options to track this down? I was ganna go get new plugs and see if that helps.

 

[iamjeff]

it is really easy to crack the porcelin on a spark plug without even knowing it...especially the #6 spark plug sinse it is kind of hard to get to. i would pull them and inspect thm for hair line fractures. that was my problem when my car started missing.

-jeff