elaketiger

I have a freshly rebuilt 94 3vze that is getting terrible gas mileage. It had a bad Knock Sensor wire (which I replaced) which was causing the timing to be retarded and I thought the gas mileage would improve when I fixed that...but it didn't. The power increased dramatically, but not the gas mileage.

I'm getting about 10mpg. Can anyone tell me the most likely issues here? I'm really at a loss because it seems to run fine.

I'm thinking that something was not adjusted correctly following the rebuild; or just a bad component. The CEL is not on.

TNRabbit

Check for stored engine codes then get back to us.

93toyrunner2

Did you have the injectors cleaned during the rebuild? Did you replace the crush washers in the injector rail fuel lines? Do you smell gas? Is the timing set correctly - 10 BTDC with the jumper set (TE1 + E1)? Are you using gas with additives, ethanol? What kind of mileage were you getting before the rebuild? Is the temperature running hot? Have you checked for codes even though the CEL is not on?

elaketiger

I bought the truck after the rebuild. The injectors were not cleaned, though. I did change the crush seals when I did the Knock Sensor repair, no gas smells. Timing is set correctly. No special fuel additives, but I'm sure ethanol has been in some of the fuel. Don't know what mileage was before the rebuild. Temperature is fine.

I have not checked for codes, sounds like the next step. I don't have a diagnostic tool, so the only way I can check them is to jumper the E1 and TE1 terminals and turn on key. How do I interpret the flashes?

93toyrunner2

Download FSM from my signature link, go to 3VZE "MFI System", "Diagnose", and there you will find the codes.

Fraser

Was all the ignition stuff replaced with the rebuild?
My runner was getting about 10mpg when I saved it from the previous owner. The plugs/wires/cap/rotor were all hammered.

skypilot

iTrader: (1)

10mpg is about normal for that truck. mine gets 15mpg but I have to use premium gas. I also have the ISR mod since its a 91 engine and I never had the correct parts. If you have the 340h trans (auto) it has a 4.30 gear to go with it.

Just for giggles run the FSM check on the distributor coil packs. I bet they are out of spec. I did some online research and one fellow found the "richporter" brand to have "in spec" coils.

Try premium gas.

elaketiger

Skypilot: This truck is out at our property in the middle of nowhere, I don't even think the gas station up there even sells Premium. He's got Diesel and Unleaded. I can't believe Toyota made a V6 truck where 10 mpg is normal. Mine does have the auto-trans which I know hurts the mileage. Is the FSM check you mentioned a CEL code check? I couldn't find anything in the manual. Thanks.

TNRabbit

10 mpg is NOT normal. You should be able to get 15-16.

Short TE1 & E1, turn key to ON, then count flashes. If steady flash twice per second; no codes. Otherwise it will flash the first number of digit, pause, then flash second digit, pause... continue until it repeats. Could be more than one code.

blake.nemitz

ya 10 is bad i get 20 around 300 miles a tank. how about your o2 sensor getting lazy,

yotasavg

That's what I used to get, now i'm down around 250-240 per tank, nothing has changed so parts must just be wearing out?

93toyrunner2

16 mpg average on my 3.0, but I am hard on the throttle driving in Atlanta traffic.
My 3.4 average - 18-19 city and 22 highway.

TNRabbit

O2 sensors need replacement about every 80,00-100,000 miles. When they start going south, you can see a 2-4 mpg decrease in fuel economy. That would be my first suggestion.

Have you been able to check for stored ECU codes yet?

yotasavg

ya codes are all good and it runs like a champ, better than ever actually... which has lead me to do a lot of head scratching...

4toy89

I get about 11 to 12 in the city and 15 to 16 hwy... but I'm lifted 4 inches with 33in tires on... I wish I got better cause it sucks getting 180 to 200 per tank

93toyrunner2

No codes - Other things to think about, check:
1. Bad O2 sensor - test per FSM to verify it is within specs.
2. Over advanced timing would cause it to have plenty of power, yet get poor fuel economy. Injectors that are not cleaned and balanced would also cause this. Tire pressure, brake drag from overtightened drums, wrong spark plugs, poor quality ignition cables, even wrong plug gap, clogged air filter.
Suggestion- Clean the intake system with Seafoam, cost $9-$10 for a can. Run it though the vacuum line in the intake plenum / throttle body, and maybe even get an extra bottle for the gas tank. This will help cleaning the injectors and the intake system of varnish and deposits. My experience with Seafoam has been outstanding as far as cleaning the injectors and the fuel intake system.