I need help I've got a 1990 accord with a f22a6 motor that I bought and have built up now everything runs but I can't get this idle surge to go away, I've replaced the iacv I've looked for vacuum leaks and tested tps sensor and verified coolant in the fast idle thermo valve also adjusted it to make sure it tight, the car idle surges from 1k rpm to 3k rpm regardless of being warm or anything I do, when I unplug the idle air control valve then I get a somewhat steady idle at 1100 rpm, adjustment on the screw does nothing I'm replacing the throttle position sensor today idk what to do the only response I get out of the car for the idle is when I unplug the map or the tps or the iacv, I cannot for the life of me figure out why I'm getting this idle surge any advice would be very appreciated. Also I don't know what this one random

wire is for if anybody knows

 

There are 3 valves on the 90-93 accords to bypass air. See the threads linked below.

To figure out whch valve(s) are allowing air to bypass, you have to plug each port with your finger while the enigine is running.

https://www.hondaaccordforum.com/for...ng-idle-64513/

https://www.hondaaccordforum.com/for...354/#post34110

 

Thanks for the reply, Ive thoroughly checked all three valves and plugged them all and the map sensor today i got curious and put my hand over the entire throttle body intake to block all air and unplugged the egr valve and plugged that and the engine continues to idle rough when i thought the car should stall as there should be no way for the engine to get enough air to run so I'm thinking maybe a bad air intake manifold gasket so tomorrow morning I'm gonna pull the whole manifold and make sure all the gaskets are new and while I'm at it I'm gonna thoroughly clean everything and make sure all the valve bypasses are seated properly aswell I will update when hopefully I get it figured out as I've been going at this surge problem for a while now and looking at what I feel like is all the documentation online about people with this problem and I'm running out of things to check.

 

if you suspect a bad intake manifold gasket before pulling it out , get a can of carb cleaner and spray it ( not overdo it)
where you suspect the leak is at, if idle goes up you found your leak if it does not there's no leak there
got enough coolant in system? try bleeding cooling system possible for air in system

 

thanks for the suggestion so for an update I replaced the manifold gasket it was missing a piece on the bottom side which is why the carb cleaner trick didn't work, now I can unplug the iacv and it will idle correctly, however it will still surge with all 3 bypass valves working I've taken off the fast idle thermo valve and taped off the holes and done the same with the iab valve and still surges, so I know those bypass valves are good, I'm not sure if I have a coolant air pocket in my iacv as it seems to be the culprit even though it's brand new, I'm not sure how to bleed the coolant tho other than adding it while I have the bleeder screw open and closing like bleeding brakes, I'm gonna try to bleed the coolant lines of air and see if that solves the issue.

 

Using the bleeder should remove most air out of the system. My oil fill funnel fits perfectly into the radiator cap area. When the engine is cold, remove the radiator cap and insert your funnel to allow coolant to expannd and push any remaining air out. Google Hopkins FloTool 10709 to see the type of funnel and you should be able to pick this up at any parts store.

The other thing you can do is remove the 7.5 amp backup/radio fuse in the engine bay fuse box for a minute with everything turned off, then reinsert the fuse. This should clear the engine computer memory. Start the car and allow it to warm to operating temperature at idle to do an idle relearn. Hopefully bleeding + idle relearn will get the idle stable.

 

So I finally solved the idle issue after replacing alot of parts it was initially the intake manifold gasket which caused me to not be able to properly troubleshoot the 3 iacs however it was indeed the fast idle thermo valve which i finally replaced and now she purs at a good 800rpm finally she is 100% good to go stock and now comes the mods thanks for all the help guys I hope this post helps someone else