Repost: power loss issue

[nativetexan]

So any ideas on my vacuum gauge readings?


http://imageshack.us/clip/my-videos/535/r7d.mp4/



Here is a video of it.

Idle seems good. When I barely push on the throttle, the engine starts to shake and then as I increase throttle it goes away. When I hit the throttle real hard, it sounds like it is backfiring in the tbi or manifold. When I increase throttle gradualy up to wherei it starts to bog, it seems like it backfires out the muffler when I let go of the throttle.

[nativetexan]

So any ideas on my vacuum gauge readings?


http://imageshack.us/clip/my-videos/535/r7d.mp4/



Here is a video of it.

Idle seems good. When I barely push on the throttle, the engine starts to shake and then as I increase throttle it goes away. When I hit the throttle real hard, it sounds like it is backfiring in the tbi or manifold. When I increase throttle gradualy up to wherei it starts to bog, it seems like it backfires out the muffler when I let go of the throttle.

Anyone?

[rsandusky]

Vaccum guage looks pretty normal. 

That tells us that the rings and valves are sealing. Also I think we can rule out a plugged exhaust.

I would check the Throttle position sensor and also the M.A.P. sensor for a bad spot with a analog meter.

[nativetexan]

I do question the MAP. I tested the TPS and it ohm'd to specs with a meter.

[Irish_Alley]

i wsa working on a geo oncecant remember what it was doing but i unplugged the map problem didnt change swapped it with one of another truck fixed the problem

[nativetexan]

Well, I did unplug it and it did get worse, but I will try to find another one. It might just be failing in that particular range huh?

[Irish_Alley]

only had it fail 100% not in a particular range

[jasong]

Native, just wondering if you found your problem? I have the exact same thing going on in my 89 V3500 with 454tbi, I have replaced all kinds of parts and still nothing. I am starting to wonder about the TPS but wondered if you come up with anything.