ford 460 power loss

I can't say if there was a power loss up till then, not having a "before and after" drive. Got the rig in October and did some "before" but no "after" drives yet. We had that over-heating catalytic converter issue mentioned earlier in the thread. Nasty!

Went for the straight pipe replacement, which is allowed here, so no more cat issues in future including any power loss from a clogged cat.

"Diagnostics first" sounds good in theory, but perhaps only for those who can do their own work. Our garage tells me that a pressure test on the cat would be about two hours work (at $100 an hour). So IMO, if you have a 1991 or whatever rig and not sure about the cat, just get rid of it, since you probably will need to anyway.

BTW in our 1991 the O2 is before the cat so there was no issue going straight pipe wrt engine dash warning lights or fuel mix etc as happens with O2 after the cat situations.

Grab a coffee, tea, or a beer and read through this thread:

https://www.ford-trucks.com/forums/1452942-1991-460-7-5l-efi-broken-down-along-the-road-again-solved.html

You will likely find your answer in there. I did, so did another user recently ;)

Good motors, have a few very basic but very important "needs"

If it runs ok after cycling the ignition I’m guessing marginal fuel pump.

You need the latest one which requires a conversion harness pigtail.

A psi gauge on the fuel line will tell the story. If the pressure ever drops below spec ( I don’t remember the number) the ECM goes wacky and it runs bad, backfires no power etc.

Cycling the key resets the ECM.

x2 on diagnostics first. I fought a fuel problem for years on an 83 460 carburated system, and finally putting a fuel pressure gauge on it revealed the problem.

A friend owns a later model 460 FI and had similar issues a few years ago. Replaced the fuel pump solved it for a short time and it re-appeared. Turns out Ford supplier provided a bad batch of in-tank fuel pumps. Replaced it again and LG* (tm) ... :)

* (Life's Good) :)

enblethen wrote:
Bad catalytic converter! Had a rental truck that ran good for short spurts then lost most of the power. Pull over, turn off engine, wait five-ten minutes, it takes off and runs good for a while.

X2.

Try to determine if it is fuel related or ignition related. If it starts good and idles fine it does not sound like a fuel pump problem to me. I would check the spark plug wires at night with the doghouse cover off. If you see arching from the wires to the engine block when you rev the engine you know the insulation in the wires has broken down. Those 460's and 454's generate a lot of heat and burn wires quickly unless you cool the engine by adding air dams or headers. This is an easy check to rule out bad wires.

DIAGNOSTICS

VERSUS

DARTBOARD

If you suspect bad fuel delivery then do a fuel delivery test. Liters per minute. Unrestricted fuel delivery stresses a pump. If it's at all weak you'll be the first to know. Starts off strong then whimpers is also very obvious.

It also allows you to check fuel clarity.

IF IF IF

This is a fuel injected engine, include testing of the "Fuel Pressure Regulator"

My 96 460 GBY didn't have a catalytic converter. Sounds like that new fuel pump is going bad. Guessing it wasn't OEM.

Somewhere along the line Ford added a different wiring harness for the new designed fuel pump that would replace their failing designed one. Your rig may be too old for that though but does make me wonder if the PO jury rigged a pump just to sell the rig.

I had a 1989 Ford rv with the 460 engine that did exactly what yours did but also it would heat up the entire under carriage to a point where the paint on the body would blister and the propane tank pressure relief valve would blow off from the excess heat. Turns out the oxygen sensors were bad which caused an over rich fuel condition which got the catalytic converter to glow red hot and fail internally and plug up so that I was only getting 4mpg and was able to only go 45mph max.

violet the gypsy wrote:
Fuel pressure seems right.

"Seems right" ? Either buy a fuel pressure gauge or rent one from a local auto parts store. Try to drive with it attached and watch to see if it drops when the problem occurs.


Is that a mass air system (with a MAF sensor) or speed density (no MAF; air flow is determined by manifold pressure)

Check the simple things, like all of the vacuum hoses. At that age I would probably just replace them. 25' of vacuum hose is pretty cheap on eBay or Amazon.