High idle - the endless saga

[Golberg]

I have a small port 4AGE which for the entirety I've had it refuses to idle under 2000 rpm.

When it was first put into a car it had a vacuum leak around the first piston's port (tested by spraying water there and it came down to the correct speed). The first thing I did was to replace the bottom injector seals with brand new ones from Toyota. This did nothing to help. So after that I actually ended up pulling the engine out and reshelling my car into a better shell. Meanwhile I had got a genuine RWD manifold and a small-to-big port adapter. So I decided to put that onto the motor instead of the old cut'n'shut manifold I had before.

This time when I assembled it all, I replaced every single gasket on the intake side with new genuine items. Got it all together, same problem, except this time I couldn't find an air leak. So I decided to pull it all off and silicone the manifold and adapter plate to the motor (because the design of the adapter plate meant that perhaps the air leak was underneath the manifold where I couldn't spray with water). Same problem, changed nothing.

At this stage I was getting pretty infuriated. So anyway, decided to go back to the cut'n'shut manifold, except this time I had it machined perfectly flat and bought another genuine gasket. I also removed every last trace of silicone from the head. Same problem!

So once again I try more things, I went and put special sealant on all the paper gaskets (3 of them) and siliconed the vacuum pot which the map and fuel pressure reg connect to too. Same problem.

So I'm officially stumped.

These are things which have been changed:
- All gaskets and seals (including the one in the vacuum distribution block on the underside of the throttle body)
- Vacuum distribution block (had another spare)
- Entire manifold
- All vacuum lines except brake booster hose

I have also put my finger over the brake booster hose, changed nothing.
Water lines are run to the throttle body as they should be.
Have also tried removing and blocking off all lines to unnecessary vacuum devices (charcoal canister, power steering pump etc) to no avail.

I'm about to pull the engine out and take it to the tip, so any last ideas I'll give it another shot.

[--Redwork--]

FUCK SAKE.... I've type a reply TWICE and this page keeps refreshing on me and wiping my measage... FUCKING ASS...


Sounds like your throttle body mate...
If you've tried two different manifolds and its still doing it then your not left with much else... Pull your intact pipe off and stick your fingers over the hole inside your throttle body... See if that helps...

[--Redwork--]

I had the same problem.... And so did a freind... Freinds was throttle body mine was a threaded bolt hole on the back of the plenum went the whole way through, stuck a bolt in and it was fine...

[Golberg]

Yeah I'll give that a shot, I know what you mean about the refresh thing though. I don't know whats up with that, but it was a massive bitch to type my initial post. Had to keep copying and pasting it to make sure I didn't lose what I wrote every time it refreshed.

[Nikkojoe]

My bigport sorta has/had the same problem, although its due to the butterfly on the throttle body I found. It does not seal up completely around the sides. Putting my hand over the throttle body made the engine stall, putting fingers over ports made it idle lower but not stall.

I adjusted it by changing the return screw position, but it made the throttle slightly sticky when fully closed.

[--Redwork--]

You can adjust that Nikko....

Just back the throttle stop right off... Then loosen the two screws on the butterfly, then open the throttle and let it snap closed a few time will center the butterfly plate, then tighten the bolts up and readjust your idle..

[Nikkojoe]

I can't loosen those two screws, already tried. They almost sheared off the heads (all my import motors have stupid tight screws). Also from memory the ends of the screws are mashed so they cannot be loosened.

[gumbie]

My bigport does this aswell, but since i run an aftermarket ecu.. i cant do anything except get a tune

[--Redwork--]

Mine is a big port, and I run an aftermarket ecu.. AND I fixed my problem..

[slydar]

the "hole" in the TB is where the crank case breather goes, a proper rwd BP intake has an internal chanel,so that the crank case is vented infront of the tb.

something to do with this might be the problem. the wrong combination of parts could be causing air to bypass your throttle.

what are you doing for the iddle control? its a thermostatically controlled valve at the base of the tb.