low mile 02 tacoma, low warm idle, already cleaned TB and IAC

Sorry for the length, just trying to be as specific as possible:

I bought a '02 tacoma about a month ago, poverty spec'd base model (2wd reg cab/2.4/5spd). Truck only has 60K miles. Seems to idle extremely low when warm; no tach but low enough to make the whole truck vibrate. Truck runs perfectly otherwise and starts right up hot or cold. All of the vacuum lines seem to be in place and in good shape.

Read the many posts about a possible defective/dirty IAC valve so I pulled the throttle body and cleaned everything. Wasn't really that dirty but with the mileage I wouldn't have expected it to be. Even went as far as removing the little stepper motor housing from the main aluminum IAC body and made sure everything rotated freely and was 100% clean. I noticed the holes in the stepper motor housing are slotted so I marked it and made sure it was aligned the same as before when reinstalling.

Got everything buttoned back up and after a short test drive the truck still idles pretty low. I can barely crack the throttle when sitting and get rpm's up to the point that I feel is a proper idle and everything is perfectly smooth.

So anyhow....just wondering what my options are? I noticed there are two different setscrew adjusters that could be used to adjust idle on the TB "side plate" (part that throttle cable hooks to): one contacting the end of a vacuum plunger thing (assuming this adjusts cold idle) and another one contacting a hard stop. They are marked with yellow caution paint. According to a few posts I've seen on the net the idle isn't supposed to be adjustable but it's pretty obvious that adjusting these would change the resting position of the butterfly valve in the TB.

Any help/insight appreciated. Only other thing I can thing of besides fudging with those adjusting screws would be the need for a valve clearance adjustment. Had a couple of sportbikes in the past with these shim adjusted DOHC setups that would progressively idle lower as the clearances tightened up over the years....but again with the mileage I wouldn't think it would need it.

 

How old are the plugs?

 

what does the LTFT and STFT show?

 

Honestly, the truck probably has the OEM plugs in it. Was gonna change them and the wires just for piece of mind but I figured I had other issues given that the truck runs perfectly otherwise and averages around 25mpg mixed driving. Even though the idle is really low it's consistent.

I don't have a scantool so no idea. If new plugs/wires don't change anything I'll see if I can borrow one and report back.

 

I'd run some kind of fuel system cleaner in a half a tank of fuel for a few days... then idle the motor with that Gunk motor flush shit for 5 minutes then change the oil and plugs...

 

removing the battery posts after the throttle body cleaning will give your truck a chance to learn the new idle process again

 

Finally had a chance to mess with this a bit more. Pulled the valve cover today and checked the valve clearances....everything was in spec....couple of intake valves near the low end (.007") but still within tolerance. Also changed the sparkplugs, they were pretty well worn but weren't showing any signs of fouling or oil burning.

Motor still idles super low when warm. Seems to idle properly when I 1st come to a stop but after sitting for a few seconds it settles down to the point it feels like the truck might stall (hasn't yet though).

Got a scangage on order but in the meantime is there anything else I can try? Check engine light hasn't ever come on when running.

Still kinda curious about the little setscrew/locknut adjuster on the throttlebody....it's my understanding that it's just to keep the TB butterfly valve from completely closing and sticking but couldn't it also be used to raise the idle a bit?

 

I would adjust that stop screw, I think that would fix the problem, you can always adj. it back. I've been working on cars for almost 60 years & realize & study all the changes/improvements that have been made.

 

this "removing the battery posts after the throttle body cleaning will give your truck a chance to learn the new idle process again"

GEARCRUNCHER knows HIS toyotas!!!!!!!!!!!!!