1991 truck 3VZE Help with diagnosis (Results of tests)
 

I have a 1991 Toyota 4WD DLX Extended cab with the 3VZE motor. Starts fine, idles high (1600 RPM or so). After 5 minutes of driving I get major power loss and won't rev over 2500 rpm. Lasts for 2 minutes then runs fine. (Sometimes if I pump the gas it helps to resolve it quicker) Never overheats, but there is coolant loss. I think a bad radiator cap because reservoir is full but radiator is low.

Ran diagnostics. I got 3 codes: 24, 31, 41. IAT, VAF, and TPS.

TPS is bad...stuck in open position. Not sure about others.

Compression test yielded 155+ on all cylinders and they held for as long as I left tester on. (I cranked the last one a few extra and it held at 170+)

I did have a little oil pudding on fill cap but oil on dipstick looks great. Previous owner only drove it on short trips to the woods. Also, when I got it, there was a brief bit of light smoke from exhaust but after sea foam treating the gas and oil that has gone away.

Took off intake plenum and the intake gasket is new looking. Some bad looking vacuum lines

Spark plugs look good. slight pale color, all consistent. Normal wear according to chart.

Can I rule out a head gasket for now and put it back together replacing the above mentioned parts and lines or would you recommend going deeper?

I went ahead and drained the oil and it is dark brown. Other than having a bit more oil in it than it should have, it looks normal. incidentally, why have I gotten no replies? Did I do something wrong with the way I posted? I made sure to research first and post as much info as possible. Any help would be appreciated.

As long as it's not overheating and there are no apparent leaks, I wouldn't worry about the hg. Did you replace the tps?

Waiting for one to come in the mail along with a new fan. Not overheating and no leaks that I can find other than the overflow because of the cap. Okay well when I get those parts I'll slap it back together and report the results. Thanks!

Help!!!!
 

It was the tps. It caused gas to get in the oil because it fooled the injectuin in to thinking it was wide open all the time

Tps is huge on the 3.0. If not right it will cause these types of problems. The other big loss of power issues with the 3.0 is the clutch fan in summer (have found no way around it) and the auto transmission. My biggest power gains were replacement of the TPS, brake power booster and swapping to a manual tranny. Now runs great.

I support the clutch fan, Jesus it's been 95+ out here in CO and the thing is running hard whenever you sit at a light for a bit. Go to take off, and there's 0 power because you're spinning a metal fan at like 3k RPM.

Check the “coolant valley underneath intake plenumz
 

Check out the valve cover gasket and the bottom of the intake plenum (to head) gasket. You will lose coolant, not see any leaks, and may or may not have it mixed externally with valve cover gasket seepage. It has the almost exact same symptoms you’re describing. Took me about two years to finally peg it down. I did all the leak down, compression, combustion gas, and every other test I could. Then when I was doing my timing belt replacement I got a better look and checked it out. This is relatively common but usually this is what it is. I believe it’s called the intake manifold gasket.
You’ll get vaccuum leak and slight overall compression loss and coolant leak through this. Sometimes a p420 for catalyst below effieviency do to coolant being burned up in the 3 and 5 cylinder’s sometimes. It gets progressively worse and usually you can see evidence of some kind of leak on top of the bell housing of the transmission, but burns off before it drips down, so you can only see it on the top where it’s VERY HARD TO SEE.

I know this is an old post, but the headgaskets can keak in several different ways and you cant always count on seeing coolant in your oil. And definitely can count in seeing it on a dipstick. I did headgaskets on a4runner the other day, and there was milkshake all in the valve covers and everywhere else,but the oil on the dipstick looked fine. Just saying,dont ever count on seeing it on the dipstick.