mfincher64

New to this site so here it is. 88 toyota pickup 4x4 m/t. Just did a total rebuild aka pistons, rings, head job, cam(stage 2 lc engineering) and timing hardware. After completion of build in stalled motor fired it up for first run and timing check. My idle is at 1800 rpms without the diag jumed. After diag jumped it drops to 1600 rpms. So I thought it maybe sacking air so I changed all vacuum lines and breather hoses. Still did the same thing. Same out come. So I figured that maybe I may have jacked up my intake gaskets. So I went ahead changed them out. Same out come. All ideas would be considered. Please help.

Hugh_Mann

Did you try the idle air adjustment screw?

mfincher64

Yes. It's screwed all the away down
Also inspected the TPS found some issues but not what was causing this one. But I replaced and set it to spec.

Hugh_Mann

I think the most common sources of high idle are vacuum leaks. You could always try spraying a can of propane/brake cleaner/carb cleaner carefully around your vacuum tubes to help check. Also, the main intake tube sometimes cracks in the bellows.

Does your truck have A/C? The A/C idle up device can cause idle issues. So can the AAV/IACV. You might benefit from cleaning out your entire throttle body if you haven't already done so. Use compressed air to blow out the air/coolant passages. Do the same to the AAV.

mfincher64

Yes it does have an a/c. I sprayed all connections and no difference found.

Hugh_Mann

Is your air flow meter working properly? How about the fuel system?

Another possibility, have you checked the throttle cable? Maybe it's too tight or got messed up somehow.

I'd really check for proper functioning of your auxiliary air valve, aka IACV/AAV. If that thing is stuck open your truck will always idle at the "cold" setting.

You could burp the cooling system again to make sure you don't have any air pockets anywhere.

Trying my best to think out loud here, lemme know how it goes.

mfincher64

I did find one of my VSV that connects to the fuel rail does have a leak. I never noticed it before but it looks like it has been broken and glued back together. Can I by - pass this or no

mfincher64

And can I by pass any of these.

mfincher64

How do I burp this motor? Also if there is air in the coolant system would this cause a high idle issue?

abecedarian

High idle speed is generally the result of either one of two things; coolant may rarely be a contributing factor:
- too much air and fuel getting in
- excessive ignition advance
If your air-bleed screw on the throttle body is fully screwed in and you're still idling high, and have no evidence of a vacuum leak, the latter is likely the issue.


If you have air conditioning, make sure its idle-up valve is operating properly, as well you should verify the power-steering's idle up valve is fine. Make sure the power brake booster servo isn't leaking; make sure the dashpot on the throttle body isn't holding the throttle open too.

mfincher64

Ok found the issue. The air valve that connects to the front of the throttle body and middle of the upper plenum that has coolant line going to it is bad. The guts inside of it are gone. Guess it broke at some point and time and blew into the intake. So can I by pass this or where can I get a replacement of it?

Hugh_Mann

It would be helpful if you posted pictures or put a name to what you're talking about.

If I were you I'd forget about bypassing systems your engine was designed with. It's there for a reason.