Without the a/c on my 3.0 runs great, nice and smooth... I turn the a/c on it idles up and everything just fine but it gets really rough. It will idle up to about 1100-1200RPM but it seems almost like a single cylinder was disconnected almost.

This past month I've been using the a/c alot and my gas mileage is really crapp this last tankful I was lucky to pull 14mpg, which its usually around 17mpg.

Any ideas?

 

Have you ever checked/adjusted your tps? it may seem unrelated but its possible that its off by a hair and while under normal load you dont notice anything, the additional load is causing defects to become more noticable. Also, I think there's a switch that kicks up the idle when the a/c is turned on. perhaps the switch is malfunctioning?

 

I'm not a 100% sure, but I do think my TPS is crap, I haven't been able to get a solid answer.

If I hook up my ohmeter to the VSA and slowly open the throttle the resistance increase for about the 1st 1/8th inch, then drops then increases all the way to full throttle. Nobody can answer my question if this is normal or not.

 

sounds like you have a burnt spot in there. I recall someone mentioning what you did and if what you mentioned happened, it was fried in one spot. However, i think they also said that you shouldnt use a digital multimeter, the needle ones are better suited for the task

did you try testing the tps the way its outlined here:
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml
and here:
http://personal.utulsa.edu/~nathan-b...93throttle.pdf

if not, it wouldnt be a bad idea. I had idle problems and power problems with my 4runner and after adjusting the tps the difference was night and day.

 

Also check the AC idle up valve ( big plastic screw on the passengerside fender where all the vacuum hoses connect) Make sure the hoses dont have holes or cracks in them.

 

not to hijack, but im trying to adjust the tps, and i cant manage to get the screws to loosen. anyone have any advice? i removed the t-stat housing to get access to the screws.

 

Run the engine in the dark and look for any spark jump from a wire. Your problem sounds EXACTLY like one that was on here a while back and that's what it was...

 

By using the needle type (analog) style multimeter is how I found the resistance drop. My digital one didn't show it as clearly... Damn anyone know where I can get a TPS on the cheap. Dealer wants $80 and I don't have any kind of money to be throwing at this other then exactly what it needs!

 

Try:

www.rockauto.com
www.car-parts.com