Advice on kids 94 4Runner: Horrible Gas Mileage, what to check? (1 Viewer)

[goneballistic]

OK here's the story: My kids' best friend got a 94 4 Runner from his dad to drive to high school. It's a v6EFI model. they had motor troubles and it seized. his dad had the motor replaced by a shop.

that was about 6-8 months ago. He's getting HORRIBLE gas mileage. Somewhere right around 6-8 MPG. It's a pretty stock looking truck, the tires are maybe 30's. No real lift or anything.

it's killing the poor kid. He loves the truck but the gas is eating him alive. I have an 81 Land Cruiser with 2F that got better mileage than that. My buddy's 92 FJ80 with 4" lift and 35"s gets better.

I am not familiar with these truck or the emission control stuff so much. They have leakdown tested it and said it tested good (I am not assuming anything is good at this point though).

What are some things I should be checking? Some of the things I think may cause mileage that bad are:

1) Slipping transmission. Doesn't seem like it is, but the car is very under powered. A v6 should be pretty peppy. it's not. So maybe the transmission is slipping. It doesn't over-rev when he accelerated but it doesn't accelerate well.

2) EGR valve messed up? not feeding exhaust gas back in making it run rich. The car passes emissions but smells "off". smells pretty rich to me.

3) injector(s) bad? - maybe bad injector causing misfire and low power. doesn't sound like it's knocking or missing though. Sounds smooth.

what else to check? wheels were not hot, doesn't appear to be dragging brakes, not sure what else to look at. It has new distributor, plugs and wires although I have not pulled them to look at them for clean or gas. Just trying to make a list of things they can look at.

any advice?

 

[Bogo]

Do a full tuneup. Check for fuel leakages. Check the injectors. Check the vacuum lines are all connected up properly. Check the catalytic converter. I found mine had a loose sparkplug which restored a couple MPG for me.

Furthermore, in the FAQ thread there are links to places with Field Service Manuals (FSM). TTORA has a good ones for that year. In the engine section is a troubleshooting table.

 

[KLF]

How did the plugs look when you did the leakdown test?

Have you checked the ECU to see if there are any codes stored?

Could be stuck injector(s), also could be a bad fuel pressure regulator.

Could be timing.

 

[2ndGenToyotaFan]

Check the trouble codes, and the timing, test the TPS (throttle position sensor) and maybe change the O2 sensor if it's old... Automatic I'm assuming? He should be able to get at least 15-16....

 

[85+92]

fuel filters suck on these chances are its never been done see if its super rusty (right frame inside rail by pass frt door)

Ive had them break the fuel lines coming from sending unit and leaking like a stuck pig

could be converter plugged up

make sure theres nothing living in the intake tube (not a joke)

im not real good with AUTO's but I think the converter can stay engaged?..or something...



EDIT: like posted above make sure the timing is right and its advancing

 

[bkg]

could also be a bad HG. Plugged cat. Poorly adjusted valves. Dirty intake/combustion chambers. Bad timing... the list goes on and on... Bogo is on the right path, IMHO - full check up time.

 

[4x4 Station Wagon]

I am leaning (guessing) towards plugged cat

 

[MaK92 4RnR]

The 3.0 is what it is. Slow, and expensive. the most you'll get out of it is maybe 16-18 mpgs on a good day. Tune ups, 5 speed, and the correct gears will help with this. I have a 92 4Runner and im getting 14-16 with 33s, 5 speed, and a low mileage / tuned motor. The best thing to do would be drop a 3.4 in it.

 

[4x4 Station Wagon]

Ya but he is getting 6-8....... not 16-18.

 

[Bogo]

What has been done so far? What are the current symptoms?

Where can gas be smelled? Is it just at the exhaust pipe, or engine compartment too? Both?

Is it stuck in 4WD mode? Other drive train drag like differentials, transfer case, and transmission?

 

[toy4xfun]

i had a problem with my wife's 95, where just one cam was a tooth off, and it ran but was lacking on the power, and sucked the gas. it really sucks to check this, with all the plastic guards.

 

[tuccing]

I had a plugged cat that resulted in horrible gas mileage once. If he drives like I did as a kid, the skinny pedal might have something to do with it.

 

[4x4 Station Wagon]

LOL Ya skinny pedal gets me too. I had a thread just like this a while back. The truck ran good but got horrible fuel mileage. I just pulled the valve cover and it has been a tooth off the whole time. But I should have guessed it and I pretty much did while trying to set the timing. The mark just didnt line up as it should.