Mileage on Toyota truck

This is a follow up on a question I posted a couple of months ago. I have a '93 Toyota 4 x 4 5 speed v6 that was getting 22.5mpg. It also had oil leaks from the valve covers. I changed the valve cover gaskets, the plenum gasket, the water return hoses and a couple vacuum hoses and the pcv valve hose. The mileage dropped to 19 and the idle went up about 100 rpm. I have checked the cold start timer and water temp sender connections, changed the vac hoses to the power steering pump and the a/c actuator. The other hoses seem good, I sprayed carb cleaner all over the top of the engine and can’t find a vac leak and the pcv valve checks out ok. I changed the brake booster and hoses because I suspected an internal vac leak in the booster. What else could I have done to kill my mileage? I know 19 ain’t bad but I miss my bragging rights and gas here is $4.50+ a gallon. The 3.5 miles is worth money, about a buck a gallon. Frustration is setting in. Any help will be greatly appreciated.

What’s your sample size for the 19MPG? The difference between 19 and 22.5 could easily be accounted for in normal driving variations. And for a V6 Toyota 4x4, even 19 mpg is unusually good-- it’s better than even the EPA’s old very optimistic numbers.

Given the increased idle speed and the work done to the vacuum lines, a vacuum leak sounds like a possibility. Unfortunately, because they’re so good at compensating for the extra air, the ol’ aerosol product/propane torch trick doesn’t work on modern fuel injected cars so it really is a matter of careful listening. Get yourself a length of garden hose and use it as a stethoscope and listen around. Also, if it hasn’t been done lately, now would be a good time to do a full tune-up including checking the timing (be sure to jump the electrical connector). Also, I don’t know if you had to remove the throttle body to change the plenum gasket, but that could have disturbed the TPS adjustment. Even if you didn’t have to, it’s still worth a check-- google “toyota TPS adjustment” and you should get a site that shows how to check it with an ohmmeter.

Thank you Jack, I’ll check the TPS and vacuum today. Sample size-months of 20-21, 3 tanks rising to 22.5 as I changed my driving, two tanks after the v-c gasket change, no real change in driving. Same routes, same times of day, etc. Way too likey to be something I did. Wanted to cover all of that before digging too much deeper. The TPS is a good call, I had to drill out a broken bolt and jarred the throttle body a bit going up and down & on and off the drill press. Could have jarred the TPS. Running platinum plugs that are a year old, wires maybe 5 years, cap & rotor same. Worth the check too.

My friend told me to just forget it as his '90 forerunner gets 10mpg. It’s a pride thing I guess. It could be called environmentally friendly too except I spend way too much time and money on this damn truck. Past the point of dimminishing returns long ago. Nice truck, that’s about all I can say for myself.

Thanks again.