[rlisak]

I just finished a PI swap. Car was a 98 GT and the heads and intake were from a 2003 with 12k miles. Romeo to Romeo swap.

Also added a 75 mm throttle body and Accufab upper plenum.

Post swap, the car hesitated and sputtered and gurgled on heavy acceleration... cruised fine... slow accel fine... 3kRPM+ accel ok but not great, heavy accel or dump the clutch ... horrible boggy mess.

Changed TPS.. voltage perfect.

Changed IAC. Idle is... eh... 800 or so and not great, but fairly steady.

No gas smell from exhaust.

I had an old Hypertech chip on the ECM and removed it, reset, no change.

Cleaned the EGR. No change

Cleaned the MAF sensor, no change.

No oil or coolant leaks.

'stomping' the throttle parked, with no load, revs respectably (not great IMO)... under load, it bogs and sputters and 'gurgles'.

Plug wires are new. plugs are new. Gap is checked and ok.

Checked wire to plug contact 100 times. Coil packs aren't new but are aftermarket and not too old (3 years)... ran fine befre PI swap.

Did the old 'starter fluid vacuum leak test.' All good.

Note that it runs better at higher RPMs, so I'm doubting timing, fuel pump, injector pressure. ie : stomping gas at higher RPMs responds better than at lower, so I'm assuming timing, fuel delivery, isn't the issue.

Alternator and batery test fine.

Oh.. and It's not throwing any codes! OBD says all is fine.. I even went out and layed on the gas to make it sputter for 15 minutes and then checked... no codes.

WHAT ELSE COULD POSSIBLY BE WRONG!!!?? * wah wah - whine *

[Military98stang]

have you gotten it tuned yet. You def need to do that if you have not. That will make it go away most likely

[NMR-2vGT]

You dont need a tune for a PI swap. My car runds fine without a tune. Any vacuum leaks? I would think you didnt get a sensor plugged all the way in as i had that problem with mine but then again you said it didnt throw any codes. And if it was a vacuum leak itd most likely be noticable at idle. But it sure wouldnt hurt to chec those out anyway.

[4.6LMadness]

The stock computer needs to go through some heat cycles before it will start running right. My car ran rich for about 2 weeks before it stopped freaking the fuck out. You will want a custom tune though because the stock PCM can only do so much with the stock tune.

[mustangracer2g]

i got a pi engine in my car and i could tell that the computer had to readjust to the a/f ratio and all

[rlisak]

As of last night, after the new IAC the car now has an idle surge. Idle is adjusted at the TB to 800 and stays there if I unplug the IAC. Revs to 4000 when I plug it back in. My car has gone insane.
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Fixed this... idle screw was loose and wiggled the throttle open... duh. I wish the rest of it was that easy.

[Antfo89]

DUDE MINE TOO! My car is doing the exact same crap and I wanna take it out to the pasture! My car feels like it has a f350 pulling it in the opposite direction when I stomp on it.