I have a '91 pickup that blew the headgaskets about a year ago. So when i put the new headgaskets on i basically rebuilt the top end of the engine and got the heads shaved and all that good stuff. It was running great until the o2 sensor went out, it threw the code so i replaced it with a bausch if that makes any difference.
It ran great after that, plenty of power and about 18 miles to the gallon. And about 3 months ago it started getting around 10 to 11 mpgs. I didn't change anything or mess with anything. Now i have turned the afm down a few clicks trying to save gas and its absolutely gutless. I took off the afm to look at it and it was spotless along with the throttle body. i checked for any vacuum leacks with some carb cleaner and i didn't find any.
Oh and its not throwing any codes. Any and all help would be appreciated

 

Have you checked the cam timing? Maybe the timing belt slipped a tooth.

 

I have not, but when i did the head gaskets i replaced the timing belt as well and that was only about 10,000 miles ago. And wouldn't the timing belt slipping a tooth effect the performance as well?

 

I also did a tune up a while back including spark plugs, plug wires, distributor cap and rotor, etc. How could the timing belt slip a tooth? i have never heard of the timing belt slipping a tooth

 

I dont have any experience with the 3vze specifically, but i have seen motors that have slipped a tooth and still run well. It is just a guess though. It could be something simple, like dragging brakes, bad gas, etc.

 

its not the brakes. how do i check if the afm and the tps are working properly? And i have heard that the bausch spark plugs don't work very well with toyotas, could that be it?

 

Get some NGK plugs.

 

what about a bausch o2 sensor? should i replace that too?

 

I checked the brakes and the passenger side rear tire is dragging. It isn't horrendous but it is definetly dragging. There wasn't enough time to fx it today. But i know that that tire isn't causing an 8 mpg drop, but it's something.

 

have you checked the fan clutch? if its working correctly there should be a slight drag on the fan turning it by hand with the engine off. if there is a significant amount of drag its stuck.

 

Today on my way home when i took it out of fifth to coast down a hill theuck completely shut off and then i put it back in fifth to start and tried it again and it happened again. I think it has something to do with the afm adjustment i made. Hopefully this helps somebody think of the issue.

 

which way did you adjust the afm?

 

Down/ leaner to try and save gas lol. I don't think it's working

 

i have mine set lean 1 click, anymore than that the idle sucked and it could'nt get out of its own way. adjust it back where it was and drive it hard to let the ecu adjust itself

 

x2 on putting the AFM back to where it was stock. Then i would remove any and all bosch products. Toyotas dont like em. Return it and get a Denso From toyota for a few extrea bucks. For plugs, denso or NGK only. Maybe coolant sensor bad causing to stay running in open loop or "limp mode" That would be obvious with an emission test as you will know exactly what its doing...Let us know what you come up with

 

x2.

I would also check for any stored ECU codes.

 

Good call Rabbit, don't know how I forgot to add that one in there