89red4x4yota

ok i did the isr mod about two weeks ago and ever since then i have been getting pretty bad gas milage, anyone have any ideas what this could be from, im stumped, i thought it was suppossed to save gas, i did it just like the write up for the 3.0 V6

Snorkeldepth

Ok, I'll say it . . . . it's got me baffled. You might just go through everything you touched during the installation to make sure that everything got put back together right. I can only speak from my own brain fades. When I did the ISR install I didn't have much light when I was finishing up. I went to start the truck and . . .. . . plenty of cranking but no combusting. It didn't take me long to realize that I hadn't plugged the coil wire back in after I'd removed it to make the ISR install easier.

Another idea, if you tweaked the brass couplings much during the install you might have torn one of the rubber grommets. The holes in the ISR tube weren't deburred during manufacture and will cut/tear the grommets pretty easy. (Again, I know this from experience.) That could cause air to be introduced between the AFM and the throttle body = BAD.

I don't see how the ISR mod, when installed properly, could cause worse mileage.

midiwall

Yeah, me nieder...



Ummm, first off, the ISR mod doesn't improve gas mileage, and like SD said, it shouldn't _directly_ cause worse mileage either.

The ISR mod (on the 3.4 or the 3.0) improves the throttle response by reducing the volume of the intake path from air box to throttle body.

How bad did your mileage get? (before/after numbers would be helpful)

Where are you in the world? What's the weather been like? What's your driving style like?

cootees

The only way I could see it causing worse gas mileage is that after you have installed it you got a heavier foot.

ChickenLover

Yeah, that's all I can think of. The new sound that comes with the ISR mod makes heavy accelerations quite tempting.

89red4x4yota

ok got some more bad news, exhaust leak...could that be what is causing poor gas mileage, i don't think it could be the isr mod either, but the exhaust leak and the isr mod happened about the same time...?

cootees

Depends on how much back pressure is being lost.

rowdy4runnin

did you remember to pull the ECU fuse after the instal?

midiwall

And if it's before or after the first O2 sensor.


Good point. Two weeks of driving will get the ECU closer to the new air flow, but pulling the fuse will get it there a lot faster.

89red4x4yota

Whats the ECU fuse?? also i went to my local muffler shop and im getting a dual catback exhaust sysyem all mendral bent. He said he bend it all for $200 plus the cost of the muffler of my choice, all 2 1/4 piping. also theres this store that sells adaptors for the stock air box that removes the enitre box and replaces it with a cone filter, between these two things im hoping ill get a little better gas mileage, as of right now im getting 13 city, i will try and get some pics posted as soon as this is all done!

midiwall

Look in the fuse box under the hood for one marked "EFI" (I think that's how it's labeled on your truck). Pull it, wait a minute, put it back in. If you can't find that fuse, then just pull off the negative battery cable, wait a minute and put it back on.

The purpose is to reset the engine computer (ECU) so that it will re-adjust to the difference in airflow response with the ISR mod.


This is the 3.0, right? 2.25" may be too large for it. I think the stock pipe on that engine is 1.75", moving up 1/2" inch from there is a LOT. If you run too large of an exhaust, you'll lose back pressure which will cost you performance and mileage.


Umm, do you take the truck off road? Is this cone a K&N? The K&N filter elements int he cones have been shown to be very poor at keeping the fine dust & dirt out of the engine that you'd find off road.

Be careful.


And what WERE you getting before?

Also, where is the exhaust leak you mentioned? Before or after the front O2 sensor?

cootees

Stock piping is actually 1 7/8" on the 3vze(just looked it up in my catalog) taking it up to 2 1/4" should be just fine any more and you will regret it. I honestly do not forsee resetting the computer on an obd1 system to be the problem you are having.

Are you sure everything else is running fine? Did you put cheap gas in? Are you pinging badly?

Mark has it with the cone filter. If you take the thing offroad then leave your airbox on.

NC-B17A

What does that mean? You don't need any back pressure at all.

89red4x4yota if you want dual exhaust then you will need to go with smaller pipe. 2.5 on a single system on a 3.0 is on the big side unless you are boosted or have rebuilt the motor & are near 200 whp. Dual 2.5 will kill your scavaging effect & thus you will loose tq & hp on a naturally aspirated eng

midiwall

I think you may have gotten involved in a conversation here about a year ago where people kept saying "back pressure" when the real issue is scavaging, which is a result of there being "resistance" in the exhaust system which also induces "back pressure".

People are used to saying "back pressure" in this sense because increase the tube size decreases back pressure, which ALSO reduces the savaging effect, which is trouble. But yes, you're right.

89red4x4yota

ok change of plans, im going to go with a borla muffler, with a simgle outlet of 2.25 tubing, and im going to make a heat box for my intake, about to go get my new digital camera so ill try to gets pics up when its all done in maybe a week