I have an '87 toyota 4runner that i just finished swapping out the motor on. New motor is bored over and has a smog legal cam. Just passed smog and runs good but noticed after climbing a grade to my house that the manifold was glowing orange. Checked timing, removed and checked cat and exhaust, o2 sensor, egr valve, and replaced fuel filter. Also checked for vacuum leaks. Motor runs good with decent power. It will only turn orange with a load on the motor and climbing a grade with higher rpm. any help would be appreciated. what else would cause to run lean or etc.

 

Never had this problem, but I would say bad cat?

 

I was thinking clogged cat, and or a fuel problem/mixture. does the exhaust smell funny?

 

Had the same issue with my 01 blazer when my cat clogged it was red hot and I had to floor it to get home, I was getting about 4 to the gallon and sucked almost a full tank down just so I didn't have to get towed, but anyway if your truck gas crap for power sounds like a cat.

 

i checked cat and exhaust. pulled the plugs and looks like lean condition.

 

You should be careful if it runs lean. I had that in my 2002 supercharged 3.4L and blew two motors before I found I needed a better fuel management. More fuel would of helped. I chipped the number 6 piston and it was causing less power. I sold the truck after a third motor. All under warranty! Thank god!

 

ok, you have a bad cat.