pennywiserawker

okay, to start off, ive got a 91 4Runner with a 22RE, custom intake, pacesetter header, magnaflow cat, cherrybomb glasspack, and 31x10.50 tires. Ive had this truck for almost 3 years and have always gotten the same gas mileage. i replaced the engine at 300,000 miles with one that had 90,000 on it (just about broken in for a yota, lol). i recently changed my head gasket and oilpan gasket.
now ive been trying to figure out why i get bad gas mileage for a 4 cylinder. i have noticed that it has always ran rich. ive timed it to 5 BTDC and replaced spark plugs and replaced the O2 sensor and still no increase. ive also notice that after about a year my O2 sensor is shot. most people that have yotas that i talk to get better gas mileage EVEN with bigger tires than mine. any ideas?!

raydouble

Been a while since I kept track of my mileage, but about 20 MPG was my average.
When you timed the ignition, did you jumper the diagnostic port?

toyota4x4907

Were you getting 14 or so before you swapped engines? What all did you swap over to the new engine? Is yours an auto or manual? And what do you mean by the o2 is shot? Do you have exhaust leaks? How old is the cat?

I got 15mpg around town with my '93 single cab 22re 5spd 4x4 with 31x10.5s...but i did get low 20's on the highway which I mostly drove.

pennywiserawker

yes i did use the jumper for the diagnostic.

pennywiserawker

ive always been getting 14 mpg since i bought it. i swapped all of the sensors and injectors (anything with a electrical plug) from my old motor to the "new one". i bought a new MAF. its a manual, and it just seems like the O2 gets clogged from it running rich. the cat was brand new as of last summer

pennywiserawker

no exhaust leaks or vacuum leaks either. could it possibly be a fuel pump or filter problem. thats just about the only thing i havent looked into yet.

toyota4x4907

You aren't getting any CEL codes, correct?
How did you figure out it's running rich?

Maybe you're calculating the mpg wrong since the speedo and odometer will be off because of the larger tires.

pennywiserawker

i know its running rich because it practically burns my eyes when driving down the road with the back window open. (my nitro powered rc car burned my eyes too) codes are correct. and im calculating it right because i put 15 gallons in on a completely dry tank and got 210 miles to it. (i ran out of gase 1/8th mile away from a gas station. lol)

raydouble

FWIW
I would recheck the timing.......... make sure its advancing and retarding when you plug into the diagnostic port.

Plumbrbob

5 BTDC may not be your sweet spot anymore since you have altered it from factory, have you tried timing it with a vaccum gauge?

Plumbrbob

I dont even use my light anymore since there is no factory setting since I am running a weber, performance intake, performance head, RV cam, & headers. it is best to use the vaccum gauge for timing performance motors

pennywiserawker

where can i get and how expensive is a vacuum gauge?

Plumbrbob

very inexpensive i got mine in a complete kit of tune up stuff It is labeled EQUUS FUEL PUMP PRESSURE/ENGINE VACUUM 3220. it will have green indicators for normal timing and red for late ign. timing. you want to connect it so it is directly recieveing vaccum from the intake. the goal is to get the needle in the green but more important to find the sweet spot where the needle is not jumping around like crazy.

pennywiserawker

thanks everybody for the info. ill check back later if with results after i use the vacuum gauge.

qdude79

PLEASE do get back to us! Mine is modified and would like to hear your results of this "vacuum timing." Mine's set a 5deg BTDC for Cali smog nazis and I know it's not optimal...

Plumbrbob

I am running a carb but it shouldnt matter, I do believe if memory serves me correctly the service manual specs my 22r motor out at 0BTDC, with my carb set correctly and my vaccum advanced pluged I dont even register on the timing tag. and it runs like a champ getting around 18city 22hwy running heavy 36" swampers on 5.29's

qdude79

Roger that, I'm just guessing that the "timing by vacuum" theory would be universal. Someone correct me if I'm wrong...

gary96360

do you have 4.10s. if so do you calculate the bigger tires into the equation?

abecedarian

if you haven't checked yet, make sure the float level is set correctly.
also, when setting the timing, the vacuum advance and retard canisters have to be disconnected and their hoses plugged... and you are confident you connected the proper hose to the proper port on the diaphragms? (advancing when you should retard and vice-versa). Is the advance plate free to move and if you have the centrifugal advance fly-weights, are they free to move as well and properly sprung / counter-weighted?

abecedarian

if you have access to an adjustable timing light, try dialing in about 34 degrees total advance and see how it goes.