89 truck lack of power,hesitation,misfire

[Ripsta7sign]

The problem has me puzzled when its cold its fine i can accelarate good it idles wonderfull i mean theres nothing wrong.but when it warms up and i accelarate it falls flat in its face it loses all the power completly.and if i floor it to wide open throttle it misfires and flames come out the throtle body.i replaced the fuel pump and filter and no luck.And theres no ses light on either.if any one can help it would be apreciated

[2000CAYukon]

Originally Posted by Ripsta7sign

The problem has me puzzled when its cold its fine i can accelarate good it idles wonderfull i mean theres nothing wrong.but when it warms up and i accelarate it falls flat in its face it loses all the power completly.and if i floor it to wide open throttle it misfires and flames come out the throtle body.i replaced the fuel pump and filter and no luck.And theres no ses light on either.if any one can help it would be apreciated

This sounds like a classic case of a plugged cat or exhaust. Drive it at night and park in a dark spot and see if the cat is glowing red. If so, the cat is clogged and needs to be replaced.

An exhaust back pressure test can also help pinpoint an exhaust restriction.

//2000CAYukon

[loganlott]

well man not looking at it i would say fuel injectors are dumping to much fuel. uh oh!

[2000CAYukon]

A bad engine coolant temp sensor can also cause it to get too much fuel when warm. If it is off far enough, you should get a check engine light. Is the check engine light on?

//2000CAYukon

[fuzzypuppy]

If it's flaming through the TB the problem points to timing and possibly ignition components, dist etc.
When the engine is started and run cold the computer advances the timing after warm up it retards the timing, this would account for the drastic change with temp rising.
A clogged cat could cause the loss of power as suggested but not the flame through the TB, and it's very doubtfull a fuel delievery problem since neither flooding or leaning will cause the flame out you described.
I'd start by checking the timing after the engine has reached temp, " when your problem exists" , if the timing looks ok check the timing after you reconnect the est wire and look at your advance when you hit the gas a bit, it sounds like your dist may not be advancing when you hit the gas after warmup.