1JZ MKIII 12MPG Consistantly and not boosting

[viperkillertt]

Like the other post. I am getting 12mpg without running any boost. I shift very carefully and after 2 months, i am still getting 12 mpg. I also do have a wideband and the car runs at like 12 AFR until warmup and then almost exactly 14.7 when warm. So yeah, i am completely baffled. I was completely expecting 20s like everyone else talked aobut. Driving 360 miles on the freeway, i averaged less then 18 mpg. I do have the Blitz ecu, but this super sucks!

I have a boost controller and actually i dont build full boost until after 3k, i think about 3500. I usually shift about 2500. For over a month i have been puttin it in 4th while i drove around town and i really havent seen any changes with that. It is a totally new build, so all fluids are brand new.

I have a really hard time believing this is all due to the Blitz ecu.

I do have a rpm bump. My rpm jumps slightly at low rpms. It is just not very smooth. If i am reving over 2 grand it is fine, just when i am holding the throttle at low rpms it bumps +/- 50rpm and slightly lurches the car.

 

[Clint]

what are you doing about fuel are you on stock pump, injectors? also you might want to replace the fuel filter it could be clogged, also what about spark plugs what are you running.

I know my 1jz gets really bad gas milage but Im running a big single and 440's with a walbro and afpr.

but If you ever want to unload that blitz ecu let me know .

 

[viperkillertt]

I am running 370s and stock pump.

I have NGK Rs in it right now. They looked pretty good, so i didnt swap in the Iridiums yet. I am going to do that when we have a nice clear day that is over 40 degrees. My stupid landlord decided he was going to expand the garage and took out an insulated wall but has now given up on the project, so it is fricken cold as hell in the garage

 

[Rich]

Checked for any fuel leaks yet? Fuel evaporates quickly, so it could be there's no puddles. When you've just parked after a drive, pop the hood and smell for fuel, could be a coupling isn't tightened properly or something.

Also check if all wheels spin freely and have the wheel alignment checked.

You say it's a totally new build, do you mean the short block has been rebuild? So, new honing pattern, new rings etc.?

 

[viperkillertt]

Checked for any fuel leaks yet? Fuel evaporates quickly, so it could be there's no puddles. When you've just parked after a drive, pop the hood and smell for fuel, could be a coupling isn't tightened properly or something.

Also check if all wheels spin freely and have the wheel alignment checked.

You say it's a totally new build, do you mean the short block has been rebuild? So, new honing pattern, new rings etc.?

Oh, no, not new engine build, just new 1jz swap. All info on engine is in my Avatar.

I have been driving her for about 2 months now. I have not found any fuel leaks. My first few fuel ups i was getting around 17mpg but it has been getting worse each fill up. about 12-13 for the last month. The car is very straight and no allignment issues. Totally straight.

 

[viperkillertt]

I have one question, where do people put the charcoal canister connections. I just remembered that i have that just sitting in my engine bay. I was told to just push it down, but currently it isn't doing anything. The canister was removed during the swap. Can i cap it off. When you mentioned fuel leak, i was thinking that might be causing a small fuel leak.

 

[viperkillertt]

Bump.

 

[flubyux2]

double check your cam timing.

ive seen 7m's that are off one tooth and they were ridiculously low on power and used lots o fuel.

 

[Element256]

Could be boost leak as well.
You have a wideband and\or AF\R ?

 

[Rich]

I have one question, where do people put the charcoal canister connections. I just remembered that i have that just sitting in my engine bay. I was told to just push it down, but currently it isn't doing anything. The canister was removed during the swap. Can i cap it off. When you mentioned fuel leak, i was thinking that might be causing a small fuel leak.

No, don't cap it off, the fuel tank 'breathes' through that. I believe it also breathes through the filler cap, but I'm not 100% of that. But it DOES breath through that line.

You can run that line downwards. I have it cut at the point where it enters the engine bay, which is where the fuel and brake lines run as well. Cut it of there and bend the tube down and back, cleanes up the engine bay a little bit more as well

 

[viperkillertt]

Could be boost leak as well.
You have a wideband and\or AF\R ?

Yup as i wrote in the original post, it is getting about 12.5 at startup and going just about 14.7 after warmup. It seems very consistent. By my a/f maps, i would think i was getting super amazing fuel millage, but it is the complete opposite. That is why i am so confused. If anything i am running lean on my maps. That is why i am so confused. I have not smelled any gas and if that little breather spot is not where it is leaving, i am really stumped.

 

[Rich]

well, that's a tough one

I can tell you boost leak has nothing to do with running rich, 1jz have map, so the ecu injects fuel based on what it reads in the manifold, whatever is leaking out between turbo and manifold doesn't effect the fuelling

 

[viperkillertt]

well, that's a tough one

I can tell you boost leak has nothing to do with running rich, 1jz have map, so the ecu injects fuel based on what it reads in the manifold, whatever is leaking out between turbo and manifold doesn't effect the fuelling

Okay, so does anyone have any ideas?

 

[viperkillertt]

Okay, i spent the night working on the supra. I think i might have fixed the problem. I have had the iridium plugs sitting around to be put in, so i finally did it. The rpm bump is totally gone! YAY!!! and the car has a freakish amount of power now!!! YES! So yeah, i just took it out and had a blast! I am going to start a new thread on a few things that i discovered. I will update after the next fuel up if the gas doesn't increase, but i think it will. One of the plugs was nearly closed. It had a gap of about .12 instead of .28. I don't know how it happened. That explains why it couldn't rev smoothly.

 

[Rich]

copy-paste from your other topic:

You might have bumped the plug to the edge of the hole when putting it in. It doesn't need that big of a tap to change the gap.

However, I don't think it was 12mm, that's about half an inch (I live in the metric side of the world)

 

[viperkillertt]

copy-paste from your other topic:

You might have bumped the plug to the edge of the hole when putting it in. It doesn't need that big of a tap to change the gap.

However, I don't think it was 12mm, that's about half an inch (I live in the metric side of the world)

Fixed.
Yes, it barely was open at all. I didnt do it, it was in the engine when i got the 1jz.