coolp51d

Hi all,

My F-150 300ci is still having power issues. A while back I was shearing distributor pins left and right (oil pump is fine) so after a road trip with 4 unplanned pit stops to replace the damn pin, I replaced the distributor. It has the TFI-IV mounted on the distributor, and I'm using the module off my old distributor. Starts up and idles just fine, but when driving it just falls on its face above about half throttle. Feathering the throttle it drives fine; I can get up in the 65-70 mph range, but if I floor it (or even around 3/4 throttle) the exhaust noise gets throaty and it loses a BUNCH of power. And forget about trying to climb a hill.

I checked the TPS and I get 1.08V throttle closed, 4.47 wide open. (Looks good to me?) Smooth change in between.

It drives better with the SPOUT unplugged and the base timing set to 10BTDC than it does plugged in. Does that mean the timing is being retarded too much when I step on the gas?

Any ideas on what else to check? I have a multimeter, oscillocope, vaccum gauge, compression gauge, etc. but no ideas on what to check. I don't get why this would happen with a brand new distributor using the same old module.

I haven't driven it much since it's such a big power loss. Could it be that the computer needs to re-calibrate for the new distributor? I don't know why it would, since only change is that the new distributor has a new PIP. If so, how many miles do I need to put on before I know if that's the problem?

Thanks for any (and I mean ANY) suggestions.

-Thomas

imp

1. The distributor drive pin, through the gear, you replaced it with the usual formed steel "roll-pin"? Much weaker than a solid pin, peened in place. Mine sheared after I installed a High-Volume oil pump. Solid pin solved problem.

2. Loss of power: likely inadequate fuel. Check fuel pressure at idle, watch for loss of pressure upon opening throttle. Culprits: clogging fuel filter, bad fuel pressure regulator, possible failing fuel pump. If ya got 2 tanks with individual pumps, see if problem persists in use of both tanks.

Just my thoughts.

imp

Edit: EEC-IV computer not sophisticated, usually can tolerate change-out of most components without a hiccup.

coolp51d

Fixed!

It turns out the new distributor had a bad hall effect sensor.

ttrimaldi

I saw this thread and hope that the original poster is still around. I am having very similar symptoms as in the original post and am trying to decide whether it's a fuel filter or pump issue, a vacuum leak issue, or an ignition issue. This truck is new to me this weekend. I drove it home 30+ miles with some minor stalling at red lights, but after I got on the interstate, it ran well and I was able to feather the throttle when leaving from a stop to keep it from stalling.

I was hoping that you could tell how you diagnosed it as a bad hall effect module.

Thanks,

Tony