Well, the truck has been acting quite weird lately..

Problem 1:

First-off, it has an odd hessitation problem..
Mostly happens when it's hot, and gets worse the more I drive it. I'll floor-it,and it'll feel like I'm draggin'a freakin' elephant behind me. You can tell it's trying to accelerate.. but the power is just not there! I only notice this really when it's hot out, and after I've been driving for 30+ minutes(mostly freeway driving mind you).. I've replaced: TPS,Fuel Filter,02 sensor, and have cleaned my MAF with some brake-cleaner within the last 5k miles. I tuned it up about 20k miles before that, but, this doesn't feel like a typical tune-up related problem.

Maybe it's got something to do with the deck-plate-mod? Big-ol-hole in the air-box, suckin' up hot air?

Like I said before,sometimes I'll floor-it, and it will accelerate, then hesitate like you stuck a rag in the intake, or like I'm pulling a big-ol' load, then sometimes it's fine... but now that I think about it, it seems, pedal-to-the-metal or just crusin' around, it lags bad do either-or.

Problem 2:
This just started happening about a week or two ago. Idling funny. Doesn't like to chill at it's normal 800-900RPM idle. Just this morning, I started her up, and the idle was jumping way up high (about 2000) and dropping down, mis-firing.. until I reved it a couple good times, then it went right back to cold-idle.

I'm thinkin' I might hafta' take My Throttle-body off, and clean it out, same with the idle air control valve.

Also, I've run sea-foam through it a couple times in the last month (both in the gas-tank, and in through the intake viz-brake-booster line.)


Any thoughts/input would be greatly appreciated!

-Dano-
<img src="/forums/images/graemlins/rolleyes.gif" alt="" />

#1 Don't use Brakleen on sensors!!!! They make other stuff for that. <img src="/forums/images/graemlins/shame.gif" alt="" />

#2 x2; give the t'body a visual and possible cleaning. Double check TPS setup while you're messing around there too.

Forgot to add..


Sometimes, specually when it's cooler out, or I havn't been driving it all day (i.e. first drive of the day/on the way to work in the mourning..) This thing is a rocket ship!

It really only lags when I drive it for a while.. <img src="/forums/images/graemlins/angry.gif" alt="" />

Oh ya, ordered a TB gasket today, should be in by thurs, so, I'll probably take the TB off on sat, and give 'er a good cleanin'..

-Dano-
<img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Yup, Problem one ONLY happens once I've driven the truck for a while.

It threw a P0510 today.. TPS Closed Loop Malfuntion.

It threw this code ALOT before.. everyday, without missing a beat. I replaced the TPS, stopped throwing the code, and truck ran a *little* better.

Now, it has throw that code a few times in the last week. I have another replacment TPS comin' (curtiosy of autozone).. but, it only seems to throw it when I'm in stop-n-go traffic, when it's hot out.

.. I'm not sure where to look next. I'm gonna take the TB apart on sat, and clean it.. Heck, I've even got a spare intake plenum, and TB, maybe I'll try throwing the spare TB on..

It is deffinatly just a problem that only happens when warm.


Not too sure where to go from here..

-Dano-
<img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I have a 2000 taco with 430K and she just started acting the same way yours is, when it is hot out,it seems like it don't want to take its gas

NICE! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Ok.. Today, while crusin' on the Freeway, goin about 70-75, the truck started to *cut-out* once I let-off the gas.

It stumbled a few times, like the fuel pump was turned off, then turned right back on..

I'm starting to think that this could be a fuel-pump problem..

-Dano-
<img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I was having some other problems with my truck about a year ago and I thought it could be the fuel pump cutting out.
The mechanic told me that these electric fuel pumps don't cut out or slowly decline in performance; they just quit working one day.
According to that guy's philosophy, the problem wouldn't be the pump.
But, if you ask me, it kind of sounds like maybe you should have someone check out your fuel pressure and make sure that pump's not failing.

Could a vacuum leak cause that? I've been surprised in the past by how much a vacuum leak can fudge up my truck's performance!

**UPDATE**

So.. I took my TB off, cleaned out just about everything that could be cleaned LOL.

Cleaned the MAF again, this time with some actual *MAF-Clean* lol

Now, a problem arises.. performance hasn't seemed to change. Still lags after driving for a while.. but now, it will NOT idle below 1100RPM.. cold idle is about 2200 rpm <img src="/forums/images/graemlins/confused.gif" alt="" />


Latley, it has been acting like the fuel pump is being shut-off entierly, then turned back on, and it will do it at random.. I cannot replicate the problem.. completly random <img src="/forums/images/graemlins/frown.gif" alt="" />

Also, when it's lagging, you can smell some sulfer-ish smell/and/or un-burnt gas from the tail pipe, like she's runnin' rich.

My MPG's have dropped considerably as well.. going from a consistant high-17-to-high 18 MPGs when loaded down, and scratching at 20MPG when empty.. to now 15MPG <img src="/forums/images/graemlins/zombie.gif" alt="" />

I drive about a good 100+ miles a day(I live in Redlands, and I'll drive anywhere from San Diego, L.A., or even as far as Baker to get to the jobsite..)

This is KILLIN' ME! lol I might as well have gotten a Tundra <img src="/forums/images/graemlins/lol.gif" alt="" />


I'm thinking, as far as the lag, maybe has something to do with the Fuel injectors.. maybe gettin' a bad signal or something once it warms up..

I'm at a loss as to what to check for next.. Fuel Trims, sensor inputs.. anything lol.. I've got a scanner where I can read data, freeze it, ect.. so, again, any input at all would be more then appreciated!
(it seems to bethat once I started working on cars for a living, I've forgotten what to do to them LOL)
<img src="/forums/images/graemlins/smile.gif" alt="" />

-Dano-
<img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Under what conditions does this happen? ie is it under slight throttle, very light pulling or, is it under more heavy throttle conditions?


TPS problems could cause both of these.. The TPS switch "home" or throttle at idle position, is what tells the ECU to begin adjusting the servo operated idle air valve to regulate the engine idle speed. If the TPS "home" switch is not closing, idle speed will be fast and unregulated by the ECU.

The TPS also signals the ECU when to do the "fuel cut" or shut off the fuel injection system when coasting and your foot is off the throttle.. Incorrect settings here cause bucking as you go from no throttle to light throttle and vice versa.

I'd recommend a very through cleaning of the throttle body including the idle air control air path in the throttle body. Same question as in the thread below.. How you "tweaked" what looks to be the idle adjustment screw on the throttle body?

Read this thread for similar problems..

The no power when giving heavy throttle sounds like a MAF problem.. Is it any better after cleaning with the proper cleaning agent as mentioned in the MAF cleaning article?.. I don't know if brake fluid cleaner will permanently trash it or not.