Hey, New member here! I posted this in noob tech, but it may be a little more complex, so I though i'd put it in here. I've got a 99 V6 S/C Tacoma with 95k, deckplate, headers, URD kit, 2.2 pulley. It has been getting terrible gas mileage for a while now. The best it can muster is about 12 miles per gallon easy driving. I have done the following to fix this problem, to no avail: The 02 sensor has been replaced with an OEM unit, MAF cleaned & resistance tested, Throttle body thoroughly cleaned, new fuel filter, air filter, new plugs, tires properly inflated, all the vacuum lines are good. The truck runs fine, no obvious problems with the way it drives. Frustrated, I took it to the dealer, as soon they saw the URD kit they didn't want to touch it. They did a few minor tests and said the didnt find anything, but didn't want to get too in depth with it, due to the kit.

The AFR's don't seem to be off, at around 14.7 and the fuel trims seem normal too. I'm stumped, Maybe it is the TPS (No Lumbergh jokes lol) sensor? It Idles pretty steady, but I had heard that the TPS can be disconnected to see if the problem lies there, if the idle changes when it is disconnected at idle. I disconnected the sensor, and the idle dropped way down, almost as if the engine was about to stall for a split second, then steadied back to where it was. Also, it seemed to idle smoother (less vibration, sounded smoother) for the short time I had the TPS disconnected too.

 

5spd or Auto? If it's an auto, than that maybe the problem. I had an '05 LR3, just before the tranny went out, it started to get about 9mpg for like 4k miles and then she started to let go.

 

It is an auto. I had the trans rebuilt about 10 thousand miles ago, but there is a bit of a weird light vibration sometimes that I can feel in the pedal when I am in drive at a stop, I can hear it too if I have the window down. (sounds like a light squeak, almost like something is rubbing) It feels like it may be coming from the trans, torque convertor area.

 

could be because of the SC. usually boosting gives worse mpg. i did notice on these 3.4l motors that u have to be very light on the throttle to even get over 17mpg. my runner 3.4 2wd auto finally gives 17mpg on mixed driving, all stock.

maybe some more sc owners can give u some insight on thier mpg's

 

The truck was getting normal mileage the first few years after putting the blower on, so I don't think its the s/c.It may be the urd kit though. When I was recording the mileage I was staying out of boost, and being very light on the throttle.

 

Bump!

 

I'm still thinking tranny but, if the URD is easiest to check out first, then start there.