As of recent, I have started experiencing two intermittent throttle-related issues. One is from initial acceleration, it feels like the engine is being choked back until I back off the throttle slightly. The other is when I am at highway speeds (65-70 mph) I feel a light drop in power when moving the accelerator and then the overdirve kicks out and then kicks back in and the throttle reponse is back.

No codes showing up and checked the fuilds and all is good with that. Also checked the tranny shift cable and it is adjusted properly. Thought maybe the TPS of MAF ?? Thought it may also be related to fuel system as I still have not fixed my gas tank that was pushed in during EC4RJ'03.

Going to pull the plugs and check them this weekend and re-check all my vac lines under the hood. Then running my diag computer from the OBD-II to see if I can find anything there after making a highway run.

Any ideas ??? Calling Gadget !!

Ricochet

You might want to also check your fuel rail pressure.. Kind of wondering about the fuel pump with the tank being pushed in...

I hadn't thought about the fuel rail but I will check that for leaks of any kind. Come to think of it occasionally when I moderately accelerate and then have to immediately stop again I do seem to remember smelling gasoline a few times but then it would clear up. Could never figure out if it was me or just driving behind someone with a gas leak problem. Maybe problem in the tank since things were pushed up and in a bit?? I appreciate the info.

Ricochet

I'd try cleaning your MAF. I had a similar problem and replacing mine cleared it up.

Thanks, I hadn't cleaned my MAF sensor in a while so I will try the as well. I checked my fuel rails and no leaks and such and all looked good in that area that I can tell. I still am wondering about my fuel tank being pushed in might have some affect on my pump pickup and such. Guess I will have to pull the tank anyway to try and get the tank pushed backout so I might as well look at replacing the pump while I am in there (going for Gadget's upgrade some time in the next few months hopefully). Of course if the hotwire is messed up on the MAF sensor then that can cause problems for sure but I will see how the cleaning goes first.

Thanks again for everyones input.

Ricochet

I would bet one shiny nickle the problem is a dirty throttle body. <img src="/forums/images/graemlins/lol.gif" alt="" />

I had the EXACT same problem a few years ago. Look here .

Good luck!

O.K., so I cleaned the MAF, actually removing it and getting to all the inner sensor wires, etc. (it was quite nasty down inside on the wire). Put it back in and test ran for a few days. Still has the same dead spot at cruising speeds, with very little throttle input. It is almost as if the throttle is dropping out a bit and then the trans is shifting out of OD, the RPMs rev up a bit, and then it goes back into OD again. Tried cleaning the TB and tested a few more days again. Same problem. So next, I checked all the connection on the TPS and other sensors on the TB and could find no problems with the connections, etc. Hooked up my AutoTap and laptop and made a few test runs, of course did not notice the pronounced dead-spot as in previous runs but I did seem to notice some strange drops in the TPS values as if I was taking my foot off the accelerator which of course causes a smaller TPS reading. But my foot did not move when this happened at a constant cruising speed on the highway. I even re-checked my tranny shift cable adjustment and tweaked it a bit to make sure the mark on the cable was flush with the cable opening as indicated in the FSM.

So, any suggestions on what else to check? I am still leaning toward my TPS going haywire, that is unless during my TB cleaning I dislodged some major crap and it is plugging up one of the orifices in the TB depending on the position of the throttle.

Before I go drop coin on a new TPS, I want to exhaust all other options. Weird symptom, very weird! <img src="/forums/images/graemlins/confused.gif" alt="" />

Suggestions welcome ..

Ricochet

Flat spot right around 2400 rpm = dirty EGR valve, esp if the t'body was gunked up when you went to clean it up.

Pull codes for the heck of it? I think the ECU will flag your check engine light with more than 2 occurances of a fault. Just another thought.

The 2000 year 3.4L 4Runner has no add on EGR system... plumbing, valves, etc.. It must use cam timing overlap or some other trick to do away with the add on hardware...

Based on your comments about the OBD-II seeing the drop in TPS values, that sounds like a strong suspect..

Sounds like the next thing is checking the resistance readings on the TPS per the FSM.. I'd look for noisy readings as you slowly turn the input shaft... sounds like the potentiometer is making bad contact at the point where it hesitates...

If you see a noisy spot, confirming that's the problem, you got nothing to loose by spraying the pot contact area with contact cleaner/lubricant.. There's a flavor of this stuff made specificly for noisey pots..

I'm assuming the pot contact area is exposed by popping the plastic cover off the TPS as can be done with older versions of Toyota TPS switches.. could be wrong on this....

I just bought one for my wife's Camry and it was only about $70.00.. Hopefully the one on the 4Runner is not too expensive..

That is kinda what things are looking like. I am going to make a few more test runs with my AutoTap and laptop just to make sure I have a consistent reference to make a determination with. I keep thinking that since most of the drive time is spent a partial throttle while on the highway, that it could be related to this seemingly dead spot on the TPS. I did take a look at the cover to the TPS and it did not look as if it was just a snap-off cover. I could be wrong though. I will probably pull it off and test it per the FSM and see what I find. Thanks for all the great suggestions. I'm gonna keep digging at this. I will post up what I find.

Ricochet