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1994 5.0 auto. ok so i just bought this truck. it was very sluggish when i got it a few weeks ago. its not my daily driver so i've slowly been working on it.

changed the air filter which was so clogged i'm not sure how it ran. then i cleaned the air intake temp sensor, Mass airflow sensor and IAC. this made it run ALOT better and helped a great bit.

now i still have a iusse at WOT, once it hits about 3800rpms it will not upshift and falls on its face and i hear a what sounds like a miss and backfire. as soon as i let off just alittle..say to 75% throttle it will upshift and run great again. it idles very smooth and 500-3500rpm is perfect no stumbles or anything. it seems to lack some power but i dont have alot to comepare how it should drive to. allthough it seems gutless compared to my '91 f-250 5.0 auto 4x4.

i will try to get a vid of what its doing to try and help. also it seems to do it worse when its warm/hot compared to cold.

i have new spark plugs waiting, i have not messed with a distributor before so i'm a bit clueless when it comes to that...but i learn quick.

thank you! any help would be great. i'll post a vid as soon as possible.:thumbup
 

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do the complete tune up. check the timing. also check the cat's make sure they are not clogged up.
 

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X2 on the clogged cats.

HowTo diagnose a plugged catalytic converter
BogHog... Use a vacuum guage, good explanation.
To diagnose a plugged catalytic converter, you can check intake vacuum or exhaust backpressure. To check intake vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Then increase engine speed to about 2,500 rpm and hold steady. Normal vacuum at idle for most engines should be 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust. Remember, though, that intake vacuum can also be affected by retarded ignition timing and valve timing. What's more, some engines are much more sensitive to small changes in intake vacuum than others, so checking backpressure rather than intake vacuum may give you a better indication of what's going on

Another suggestion by BogHog was to remove the O2 sensor in front of the Cat (which will allow the exhaust gases an avenue of escape) and see if the engine runs better. If it does, the Cat is plugged.

Plugged Cat test with pressure guage...
http://www.youtube.com/watch?v=IzyvL5tQLzU
 
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