johnboywalnut

This is my first visit and first post.
I own a '03 Tacoma Prerunner W/3.4L S/C A/T.
It's had the S/C for 15K of its 25K miles and always run well.
I now have very intermittent powerloss under light acceleration. Just over 2K rpm the boost falls into a vacuum and more throttle is required. Heavy or full throttle feels normal. I have replaced the actuator diaphram per TRD recomendation. My throttle response feels better but I still have the same problem. Any input is welcome. Thank You

Other mods: TRD thermostat, cooler plugs, Split Second FTC 017 w/minimal timing reduction under 3K rpm only.

I am new at this, so any any advice about posting is also welcome.

Gadget

Does your engine have the throttle by wire system on it?

Gadget

johnboywalnut

Thanks for your reply Gadget, No it does not have throttle by wire. Today I replaced the IAC check valve, on my way home the symptom happened again. Have you ever seen those Split Second FTC 017 units fail or cause symptoms like these? It is the most recent addition before my problems started. It was in for a few months before symptoms. The installation was done well with solder and heat shrink. Even if I zero out all settings the symptom recurs. I am considering removing the unit just to eliminate it as a possibility. Only one time this happened entering the freeway, I held the throttle steady to see how long it continued, after about ten seconds the check engine light came on. I pulled over shut the truck off, restarted it and the light was off. The next day I checked for codes excited that I may finally have a lead, but found none. I am grasping at straws. Any ideas? Thanks again. John H.

MTL_4runner

Might also want to check your TPS and see if that isn't the culprit.

lee

despite the fact that im mechanically ignorant, i can tell you the source of my recent power loss on my 3.4 was the MAF.

so.. check the MAF

Gadget

The thing that gets my attension is you are saying there is a loss of boost when you are holding the throttle steady. Boost is strickly a mechanical function of throttle possition and RPM. The FTC in no way can affect boost.

If my uderstanding of what is going on is correct then you need to look for things that affect boost. Look for a slipping belt and check the bypass valve actuator. If the diaphram is bad in the actuator you will have weird things happening with boost independant of throttle changes.

Gadget

rimpainter.com

Isn't the truck and SC'r under warranty? Why not take it in?

(Since this isn't your basic and common pinging problem)

johnboywalnut

Thank You for all your input, I am going to monitor as many parameters as I can this week. Thanks Gadget for the clues I didn't think about the belt slipping. I have already changed the actuator and the check valve. I will keep checking in and posting replies untill I have this thing fixed.

Gadget

Well, if you have a varience in boost, then something is messed up. There are only few things that can cause it.

Do let me know what it ends up being when you figure it out.

Gadget

johnboywalnut

Well I think it is fixed, Gadget I can't thank you enough for pointing out the obvious. I put a new belt on it and have not had a problem for a hundred miles or so. I will post again either way, but I am all smiles right now.

johnboywalnut

Hello Yota Fans, I am Happy to report that my truck is finally fixed. The problem turned out to be one of the wires at the accelaration sensor, it had backed out of it's cavity and was losing connection. I did not know that this truck had an electronic throttle plate or I would have poked around there sooner. Special thanks to Gadget, John H.