truck running sluggish... fuel issues perhaps?

[Good Times]

Vehicle: 2003 4runner v8 full time 4wd
Specs: v8, stock exhaust (sort of), stock air filter, custom fuel tank, custom everything else that doesn't affect the fuel.

Link to my vehicle's current status: Operation Rebuild Chaos Edition (http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=2318.0) Thread

Problem: Truck runs sluggish like it doesn't want to go anywhere

Symptoms: Has decent (but you can tell it's sluggish) accelerations on flat surface but will have zero umph on incline surface; Enough that I can floor the pedal and nothing happens. I don't even get the roaring v8 sound.

Symptoms occurred after the fuel cell installation.

Potential Reasons: Custom fuel tank using factory fuel pump.

Attempted: Originally had a Camry fuel pump and experienced the same issues so I swapped it out with the 4runner fuel pump. But when I had the Camry fuel pump I didn't have an exhaust installed so I figured it was the lack of the restriction required that caused the loss in torque. After the 4runner fuel pump was installed the problem remains. I did disconnect the battery so it'll reprogram my driving habits etc but no dice. :(

I'm out of ideas on what to try next. I can't reinstall the stock fuel tank because of the 4link setup I have so I need to try something else. I'm at a loss as to what variables to eliminate because the only way to test the sluggishness is by driving it.

No fuel leaks from the fuel lines nor am I smelling any fuel from the exhaust.

Any of ya guys got any creative ideas?

[Good Times]

O yeah I totally forgot about pull codes to see haha man I'm such a nub :D

And yes this happened after the coilovers were installed. But the truck is pretty much level and I still do need to recalibrate the zero level for the deceleration sensors etc.

Fuel filter is good, the lines are good. Have to check the injectors still.

The only bummer part is that autozone doesn't loan out scanners anymore :( damn it!

[Good Times]

yeah I am a cheap a$$ :)

Guess I'll be picking one up... bah! eh we'll see. Got other toys to buy too... gotta budget accordingly :D

[slosurfer]

It's not your tranny slipping is it? :(

[paddlenbike]

Do you have a check engine light? It doesn't take much to trigger it if you are running rich or lean. I've had a dirty airfilter trigger mine in Death Valley. You'll know by the P0171 code (or whatever it is).

Is the fuel tank properly vented? It's not started to collapse in on itself is it?

With as hard as you hit, I wonder if the materials inside the catyletic converter broke up. Sometimes when that happens the honeycomb orients itself sideways and causes massive exhaust restriction.

Just throwing out ideas.

[corax]

my first step would be to hook up a fuel pressure gauge and monitor it while driving, then a vacuum gauge and monitor while driving -> hears an article with a neat little animation of the different things the gauge might do CLICK ME (http://www.secondchancegarage.com/public/186.cfm)

[Good Times]

The truck is fixed! Surprisingly the problem had nothing to do with the fuel... Go figure.

Bob picked up a fuel/vacuum pressure gauge for me and we did a quick tap to see if the fuel pump was working and surprise, surprise it worked to specification so that really threw a really big curve ball. Since we eliminated the fuel pump being the issue we moved forward to the engine.

Thought the throttle body might be dirty or causing some issues (damn electronics) so I took it apart to do a good cleaning. After cleaning the tb, we performed the same test and still had the same problem.

We did check the CEL to see if there were any codes but surprisingly nothing so that didn't help at all. After spending a good day tearing apart into various parts we decided to call it a day. I spent the next few days reading the service manual to see if I can trace any other ideas.

We checked the tranny oil and it appeared that it could use a bit more oil so we gave her a bit more to make sure she doesn't get cranky on me. That didn't resolve the sluggishness so I really got stumped. A million different possibilities came into my mind such as a bad motor, tranny, ecu you name it. Just when I thought all hell was about to break loose by me just kicking the bucket at it, I thought I'd check on the ECU.

Since these newer trucks are all controlled by these stupid computers I thought there might be something that's causing the truck to be non-responsible to my skinny pedal being mashed in. Since I replaced the ABS line I checked to see if the computer had to be recalibrated. Looking at the service manual didn't help me much but after a bit of poking around asking I found that Toyota had a TSB on how to recalibrate the zero point of the yaw rate and the deceleration sensors. Once I found this I knew this had to be it since it wasn't throwing any CEL codes but something was preventing me from driving this pos!

After reading the TSB I gave it a whirl this past Thursday. The recalibration test took about 15 minutes (I fubared 4 times due to me being a chicken shorting the ODB port). Anyway after doing this test I gave the truck a drive in my driveway (all of 75 feet) and boy was the throttle response IMMEDIATE!!!

So now that I've fixed this, I can truly say these stupid computers are RETARDED :)

Btw, if you guys want to read up on the dumb recalibration test, here's the thread (http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=6377.new#new).

Thanks for all of the suggestions! I never thought it'd be computer related but go figure.

[DHC6twinotter]

Awesome!

Lance, was the lack of power you were talking about at Pismo a result of the ECU and not a lack of exhaust? The 4Runner sounded really sweet with the "exhaust" you had on it at Pismo. If I can run a 2uz in a hot rod or crawler with just headers or straight pipe with no adverse effects, I may be temped to do so. If I can get away with it. :hillbill:

[Good Times]

Daniel,

I'm sure it's possible but I know w/o the exhaust you will lose a bit of torque from the lack of the resistance required. It definitely sounded great but I tell ya driving around the block definitely doesn't bring smiles to my neighbors!

[DHC6twinotter]

Thanks Lance. I was wondering about the torque issue too, so that answered that question.

[Good Times]

Daniel,

Once I get a few runs under my belt I'll give it a whirl w/o the exhaust and get back to you. No promises of course since my first tentative run won't be until late feb!

[YotaFun]

Lance, are you still wondering about how to pass the emissions like you mentioned at Pismo?

[Good Times]

Avy,

Nah I should be 100% street legal now that I've got an exhaust on there. Heck it's a factory Toyota one too! :D