Sansocal

My 92 truck with a 3vze got around 8 mpg, i checked the timing and it was off by 20 degrees, set it back to 10 before and it felt like a nascar but only got 11 mpg. I pulled some codes and got a code 64. deleted the code and drove around the block, it came back. checked the wiring at the ecm, its fine. today i took it to the transmission shop. he is gonna replace the tc lockup solenoid.

could a bad/intermittent tc lockup solenoid be unoticable and still cause horrendous gas mileage?

btw, the truck has 3.88 gears and 31 inch tires and the freeway brake pedal/unlock test looked fine

88toyblackjack

Did it feel like it was slipping at highway speeds, or maybe not shifting all the way up?
When I bought mine the shift solonoids were not working. The truck had sat Idle for a couple of years. It was stuck in 1st. I changed the fluid, pan filter, and installed a spin on external filter, added B&M trickshift and lucas. I prolly changed the spin on filter three or 4 times before 3rd gear started working. Check the temp switch on the back of the intake manifold(there is 3). I changed this out and OD and lockup started working immediatly.
Mine has severe engine issues since I brought it home, and I still got between 12 and 20 mpg(I have a knock sensor wire issue among other things).
I'm no expert, this was just my experience. $60 switch, 1 hr change out vrs Big $$$s at a tranny shop. Its worth checking.

scuba

3.88 gears? Is that a typo that was meant to be 4.88 gears?

Sansocal

yeah, my bad 4.88 gears.

It never felt like the tranny was slipping, but then again i have never drivin a toy truck other than this one. the reason i sent it to the shop was to rule out the tranny as being the culprit of bad mpg. if this doesnt fix it, then its got to be in the engine, right?

88toyblackjack

The nightmare is...... Our trannys are computer controlled. Temp sensors, speed sensors, air flow sensors, tps sensors all contribute to shift times and qualities. It can be overwhelming. I busted out the manuals, a multimeter and went to checking. Its definitley easier to have somebody with the right equipment check it, but where I am at I have ZERO faith in any shop. They only train to be parts changers these days, not mechanics.

88toyblackjack

Kinda got focused on the transmission issue, and forgot the main topic was fuel economy. I would start with the simple stuff. Oil, fuel and air filters, oil change. Check for vacume leaks around the manifold and vac hoses. What kind of shape are the spark plugs/wires. PCV valve? Cap and rotor? Did you use a jumper wire when adjusting your timing back? Vacume leaks, will affect idle, which in turn affects timing etc.
I bought the haynes, chilton and a FSM to get most of the information on all the electrical and sensor checks. My PO had jimmyjacked the idle speed, TPS, timing and broke a couple of the temp switches on the back of the manifold. I think I had all 3 manuals commited to memory before I got it worked out

Sansocal

I have checked most of the sensors, o2, vafm, ect, csi... havent checked the tps.

i made sure the cold start injectors wasnt leaking, and set the timing with the te1-e1 jumped.

the plugs, wires, pcv, cap and rotor are brand new.

so are all the belts and headgasket.

have checked for vacuum leaks and there are none.

I would like to find a way to test to see if the truck is coming out of closed loop efi?

Sansocal

got the truck back today, doesnt feel much different other than expected of a tranny service (harder shifting, nice smellin atf, ect.) i guess i gotta fill it up and see if mpgs went up.

anyone want to buy a 92 sr5? lol

88toyblackjack

I have read that the type of plugs and wires will have a impact on mileage. The general consensus is stick with the Factory wires, and factory NGK plugs. My wires are orig, with over 300K, plugs are NGK 1 step up hotter.(I burn lotsa oil). I have always held the thought that Japanese run best with NGK, European on Bosch, dodhge on champion, Ford on Motorcraft, and GM on delco. I put a set of bosch platinum plugs in a new 89 F250 one time and saw my mileage drop from 15 to 9. They did not stay too long.
Have you checked for any restrictions in the intake in front of the air filter? how about on the exhaust side? Cat plugged?