Mechanics

LOOPES AND BACKFIRING WHILE IDLE

2002 Ford F-150 • 308,000 miles

Hears the deal; this all started when I changed the spark plugs. Truck ran fine I was just doing pms. Changing the plugs ended up with having to rethread one of the coil pack bolt holes in the intake. One that was repaired I installed new upper and lower intake gaskets, torqured everything to specs, installed 2 new coil packs (broke 2 getting them out), replaced all 8 plugs with ngk oem replacements, buttoned everything up and to my suprise this lopeing and sounds like intake backfiring. Please help! Engine is a tritron 4.6
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Tmaj9447
May 24, 2012.



Go to this link: http://www.2carpros.com/articles/engine-backfires-while-running

Rasmataz
May 24, 2012.
Checked fuel pressure at rail 40 psi

Tiny
Tmaj9447
May 24, 2012.
If this helps rpm goes from 700 to 1500 radically.

Tiny
Tmaj9447
May 24, 2012.
Check for vacuum leak and clean the idle air control valve and see what happens

Rasmataz
May 25, 2012.
Okay still no change, I took the 4 spark plugs on the rightside out and they are sooted and dry. Should I check the injectors, seems like it is not getting fuel to the cylinders. Not sure

Tiny
Tmaj9447
May 25, 2012.
Lower intake gasket, replaced and runs as expected. Vacuum issue solved. Thanks!

Tiny
Tmaj9447
May 25, 2012.
Or pleasure. Happy to help.

Closing thread.

Rivermikerat
Jun 1, 2012.