Walisambum

I bought this pick up truck , a 1996 T100 3.4L V6 5VZ -FE, and I bet u the truck consumes like hell abt double its usual3.4l to now 6.8L and it has been pretty expensive on fuel. Changed the spark plugs and injector but trouble persist. I was thinking that it could be the ECU that probably need re mapping but I think again that if it was the case the glutton wouldn't start and drives well like it does. Thanks for any council that can point me to how best can save on fuel, coz running it is really too expensive. Great and powerful truck though, I think if toyota made it to drink this much then the 5VZ engine wouldn't have seen the market.

maachine

what kind of mileage you getting?

Walisambum

I get the regular 1200

Walisambum

maachine , was wondering, do u think the high fuel consumption has something to do with the mileage? If yes could u pls clarify on that. Thanks

Zpd426

What size tires? Does it have aftermarket gears?

What is your miles per gallon? With my 33s and 488 gears i get 15 highway 13 city.

I think normal is closer to 19 highway 15 city...

maachine

yes i meant gas mileage not mileage on the vehicle. cause if you're getting mid teens around town to 20 mpg on the highway, its normal

Walisambum

Thank u Zpd426 for giving an ear to my predicament. I thing
K my tyres are not the issue, besides I got standard tyres for a normal pickup.

Ok maachine I get it, u see this thing really consume and I mean it. Actually I get abt 9 in city and 11 to 12 on the highway as to what we call normal which has to be at 15 in traffic and abt 20 on the high way.
At idling the exhaust gases are slightly dark and after abt an hours run where u step on the gas the plugs look just too clean. But after a long descend the same plugs are dark as soot all covered in carbon. I know the injectors are spraying too much , and I replacing them yet the problem still here. I think its the ECU but again the vehicle starts and runs well. Is there a fuel economy system on this thing.

maachine

you may have a vacuum leak and the computer is over compensating with large doses of gas to equal out the mixture. does the exhaust smell like gas?

Walisambum

Man u are starting to make sense, "A vacuum leak" that adds up to something. My exhaust smell like petrol big time. Getting its stench u wld tell its getting an incomplete combustion. Mixture too rich!

Ok man talking about the vacuum leak what are the possible areas for this. Around the inlet manifold gaskets? Where else? Checking it out right away. Please do point me, if u have some bright ideas. Good thinking men! Thanks

CJM

A bad oxygen sensor will also cause a rich state and cause the truck to dump fuel like no tomorrow.

Walisambum

Thank u CJM for ur brilliant suggestion though, I thought that a faulty oxygen sensor should cause the check engine light to come on. But its not the case. Here immediately I crank the Engine, a few seconds later my panel is clear with all lights off.

maachine

Its a possibility that it hasnt thrown the code yet. It could be a potential fault stored in the comp that hasnt thrown a code just yet. Might try running to autozone and hhave them scan it to see. Regarding vacuum leak, go throigh the whole intake system and make sure there are no open holes, loose clamps or damaged hoses. Look around the throttle body especially and trace any hoses coming off of it. You can also get a can of starting fluid and spray it around, if you hear the engine rev, you have a leak. Just be careful of potential fire when you do that.

Walisambum

maachine u seem very good with these machines. Ur diagnostic methods are that of a pro aimed at getting accurate result.

Was careful about a possible fire with the starting can test, lol. Was amazing , almost emptied the whole can while having fun with it when I realised I could throttle the engine with sprays at the inlet (air filter body). So to say. The Vacuum test was performed and sorry it tested -ve. Engine could only breath the ex fuel around the air filter. Will leave the car at the service shop on Monday for the ECU scan and find out what it turns out like. Was thinking, what if I replace the injectors with smaller 1s just like the old trick with a carburettor jet.

maachine

i wouldnt do that. there is obviously a problem and spending money on smaller injectors (band aid fix) wont fix that problem. sorry i couldnt help you figure it out. hard to diagnose over the internet. good luck

CJM

Often these trucks dont throw a code for the sensors even if they are bad. They are pretty easy to replace tho. Make sure you buy denso or ngk and not bosch-our trucks dont like them.

Oh and not sure the exact mpg your getting but I get roughly 15 in town/17 hwy.

Walisambum

thank u man u have been of great help so far. I will heed ur advice and refrain from buying the smaller injectors. I'll inform about the out come of the scan.
CJM what ever the outcome of the scan I will request an oxygen sensor check. also my mpg is 9 city and 12 high way. Pretty disappointing isn't it. My truck has a really bad disease

BamZipPow

Shoot some video of yer engine running as well as when yer driving and post it.

Is the engine stumbling or running rough? Have you cleaned the MAF and reset the ECU (pull the EFI fuse fer at least 3 minutes)? Have you inspected the vacuum line to the fuel pressure regulator? If it's split/burned/leaking, it will allow too much fuel pressure which would cause the injectors to spray more fuel out of the injectors.

The best thing you can do is to hook up a computer to the OBDII port and see what the sensors are telling you. Is the engine staying in open or closed loop after the coolant is at temp? What temp is the engine coolant temperature sensor reporting the temperature to be? The ECT sensor is what ECU relies on fer coolant/engine temps...which is not the same sensor fer the instrument gauge.

The best way to test fer a vacuum leak is with propane gas. With the engine running, run the unlit propane torch nozzle around each vacuum hose connection and see if the engine RPMs rev up or not.

totallyt100

does it stumble on engine load like hard accel might be coil packs breaking down. bad fuel regulator will causing bad fuel economy. o2 sensor bad burns a lot of fuel. mass air flow bad will do the same and usually dont throw codes. bad injector like leaking and trying to reburn on exhaust stroke this should leave a miss fire code. then you move injector to another cylinder and see missfire move. is away to check injector in driveway

totallyt100

a smoke machine is the best way to check for vacuum leaks