TROUBLESHOOTER

I have a 1992 Toyota pick up truck with a 3.0. It has been losing power for a while now. Today it would not get above 45 mph. It revs but it will not pick up speed. Transmission is OK, and not slipping. Sometimes it will not rev above 3500 rpm in park. Pretty sure it has 4:56 gears as it is Auto with factory tow package 31-10.50-15 tires (I did just put 33-10.50-15s on but had same issue before tires)
Parts I have changed as follows.
New ECM (remanufactured)
New distributor
New cap
New rotor
New plug wires, new iridium spark plugs (tried cheapo NGK too).
New coil
New engine coolant temperature sensor.
New throttle position sensor. New throttle cable.
New O2 sensor.
Grounded and cleaned grounds everywhere
All of the above were changed to fix a trouble light (code 12, 14) with stalling randomly. ECM solved this issue and all was well for a few months. Then the truck started losing power.
I have changed the Fuel Filter.
I have tested Fuel pressure -- 40 PSI idling --38 PSI reving --60 PSI with return line crimped.
Base timing is set to 12 deg. (tried 10 deg. also)
I have opened and cleaned the contacts in the VFM (sp?) Air flow sensor. It Ohms out good.
no vacuum leaks to be seen
replaced the rubber boot that hooks to the throttle body.
truck seems to start and idle fine, just has no power, it takes 10 miles (on flat ground) to get up to 55 mph ( this is no exaggeration).
what should i check next?
FIXED!!

Catalytic Converter was crumbling. Replace it, muffler, and tail pipe for the final fix.

coopster

Not financial or mechanic advice.
It seems that you've probably got good spark and timing what with all the parts. You did try (is it carb cleaner?) on vacuum lines? But a leak would make it idle/run rough I'd think.
I've found using a brake bleeder vacuum hand pump is a really good way to check for vacuum leaks. (And testing VSVs).
If it was smoking you'da said so. Altho at this point - if I was certain it wasn't something to do with transmission - I might go back and check compression.
Could also just be poor fuel delivery or pattern from injectors. But all six? At once?

The factory manual has (IIRC) a trouble shooting matrix. If you can find one. I was thinking theres one Scope or someone posted a link to. Maybe in this forum thread stickies.

BTW my 95 came with the 4.88's. Auto/tow package. Good luck

TROUBLESHOOTER

Thanks for the response Coopster. I finally got it fixed. After 3 years of owning the truck and living with NO POWER to accelerate or pass .... it was.......(drumroll here please)......The catalytic converter crumbling and plugging itself up. Replaced it with a high flow type and increased the pipe diameter to 2.25" out and a magnaflow muffler. With all new electronics and etc the power is back. Feels like i got a new truck! Also, MPG went from 14.2 to 16.2. Now I can move on to working on the rest of the truck.