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Need some help guys, this truck is kicking my ass. It's my dads old 01 F150 king ranch with the 5.4L. It spit out a spark plug and I had some PI 4.6l heads off a romeo mustang sitting around. I slapped them on, got it all back together and now it's doing something weird.
Fire it up and it runs great in the upper RPM range, say about 2K RPM and above. Let it idle and it surges big time. Dips to almost dying, then surges back up to 1200RPM or so. It's also popping and backfiring through the intake when this happens.
Thought I got the timing off, so I pulled the valve covers and the timing marks are still lined up where they're supposed to be. On top of that, I thought it would have PTV issues if it was even off a tooth. So far I have done:
So yeah, I am stumped here. I hear the cat converters crackling like it's dumping raw fuel. Unplugging the MAF helps some, but it still surges badly. I'm completely demoralized and need some ideas.
Going to check the fuel injectors next, but I doubt that they're bad. Any ideas?
Fire it up and it runs great in the upper RPM range, say about 2K RPM and above. Let it idle and it surges big time. Dips to almost dying, then surges back up to 1200RPM or so. It's also popping and backfiring through the intake when this happens.
Thought I got the timing off, so I pulled the valve covers and the timing marks are still lined up where they're supposed to be. On top of that, I thought it would have PTV issues if it was even off a tooth. So far I have done:
- Checked codes, there are none
- Checked Compression. 185PSI on all cylinders
- Checked for vacuum leaks, found none
- Checked timing, appears OK
- Checked fuel pressure, normal.
So yeah, I am stumped here. I hear the cat converters crackling like it's dumping raw fuel. Unplugging the MAF helps some, but it still surges badly. I'm completely demoralized and need some ideas.
Going to check the fuel injectors next, but I doubt that they're bad. Any ideas?
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