[brock]

i own a 91 351... ive replaced just about every tune up part you can think of. actually, ive replaced every part you can think of. when coming from a dead stop and accelerating theres a dip in the motion before my truck starts picking up good. itll start off the line ok but then it seems to make a dip in the power before picking up again. also i tested my TPS sensor and the idle voltage is fine but at WOT it only reads at 3.5 about, instead of the 4-5 its supposed to be, and when i try flooring it the thing just accelerates in that gear more instead of taking off. any idea how to fix the WOT TPS problem, and what the hesitation i guess might be

 

[95_bronco_limited]

Check O2 sensors and Idle Air Control Valve. My money is on the IAC though.

 

[imlikeojnow]

Clogged cat. Do you have a haynes manual it has a real detailed description on testing the TPS. if you arnt getting full voltage it says to change it with a new one

 

[MrBob]

OK... here are a few good places to look:

EGR opening too soon.. will give this exact symtom... try disconnecting it..
IAC motor
Poor exhaust flow
igniting timing
wrong spark plug wire routing... not firing order, but there is a specific way these have to be run..... very easy to do and causes problems like this

A few good places to start...

Bob

 

[SigEpBlue]

I know that little "tip-in" problem all too well. On my rig, it was EGR-related. Replacing the EVP helped out more than anything, but I can still feel it if the engine's not completely warmed up. Pretty sure it comes down to bad mapping and bumped timing, but I'm still thinking of making a restrictor plate for it.

Pull out your Haynes manual & DVOM, and test your EVP sensor; it's the white plastic piece on top of the EGR valve, with three small ears and an electrical connector. When you're watching the resistance change, make SURE that it's not decreasing THEN increasing when the rod is moved just off-rest. That's the most-common failure I see in these bastard-design sensors. They just don't last, in my experience.

Also might want to check that TPS.