i have a 87 van fuel injected it hesitates when u touch the gas but when you step on it it go's.?

Question

do you know why?

Answer 1

Sensor readings Ox, MAP and leaky vacuum lines, TPS, air volume or air temp

Contaminated or old fuel

Clogged fuel filters

Dirty or partially clogged Injectors

Low pressure from in-tank pump


Sensor readings:
Ox sensor can be lying to the computer saying the mix is too lean or too rich

MAP sensor can be lying to the computer saying the manifold vacuum is higher or lower than what really exists. Leaking vacuum hoses are common problems here.

TPS can have a worn spot in the normal cruise position giving a false throttle position.

Injectors can have external carbon buildups that interferes with spray pattern or can be partially clogged.

Low pressure from the in-tank pump can cause a lean mix at cruise if the injectors are maxed.

If the van runs better cold, look for things that cause a lean mix as computer provides a richer mix during warmup.


Wide open throttle operation covers up a lot of sins for two reasons.

1. Many fuel delivery systems will boost fuel pressure to the injectors at WOT which covers up some lean mixes and will flywheel through on rich mixes (lots 'o air).

2. TPS is in a rarely used area of the sensor and is usually clean whereas the cruise position can be dirty and sends a signal with static or no signal to the computer causing computer confusion.

Answer 2

TPS (throttle position sensor) if it's GMC, Chevy.