so blew the head gasket on my crx 1990

but in a 1.6 replacing the 1.5 engine

runs nice but after driving for a while after it reaches op temp or if it's hot out the idle bounces up and down

when just driving in the beginning when engine is cold it's fine or if it is cold/cooler outside but after around 45 mins. or stuck in traffic idle starts revving up and down, it never did this with the other engine

any thoughts?

my mechanic said he cleaned out the throttle body, not sure of this though, he may be full of ****, it never did this with the old engine.

 

youve got a slight vacuum leak. the IACV is trying to compensate but cant.

ppl are going to tell you your TPS or IACV is bad and needs replacement. i say its just your idle screw that needs adjustment.

theres a procedure in the helms manual on how to properly adjust your idle. this is one of the rare times i say ignore it.

just turn the idle screw all the way in while its running. if the engine does not bog or stop cycling the idle, then youve got a serious leak you need to find and address. if it does bog, then thats good, just unscrew the adjuster out until youre back at the right RPM, should be about 750rpm, unloaded.

 

I'm sure my mechanic did this he said he adjusted the idle ...

if it does bog and I re-set it then it will still do the same thing won't fix it.

it idles fine in cool weather or when the engine is cold

if I remove the iacv and do it myself do I have to flush the whole cooling system and refill it again?

 

b4 I put in new rad a little while ago used that powder rad stop leak ****.

have flushed the rad since then but could some of that crap gotten into the iacv?

 

there are bad ways to reset the idle. try my way.

ugh... yeah, that stop leak stuff is crap. ruins the whole system. sorry man, cant help you with that.


you can also try bleeding the system again. make sure theres not an air bubble.

 

https://honda-tech.com/forums/acura-integra-6/%2A%2A%2Ahow-clean%2A%2A%2A-your-iacv-k-idle-air-control-valve-1575913/

If you remove the iacv to clean it you don't have to empty or flush the coolant system. just pinch off both the lines so they dont leak everywhere once you take them off the iacv. once you have it back in place just remove the rad. cap and let it run for a few mins to get all the air out. Also you might try replacing the $4 iacv seal between it and the intake manifold. After i broke my iacv loose to install it on my new intake mani the seal was shot and wouldn't seal. it looked fine but eventually i figured what the hell i'll replace it cause i'm running out of things to try. Sure enough the surging idle went away.

 

thanks man

where can I get the seal, is it universal? autozone etc.?

 

no unfortunately not. you'll have to special order one from a honda dealership parts department. i looked around majestic hondas website but couldnt find the seal through them.

 

You can also get a can of carb cleaner and get the engine hot. Then just spray around the engine (mainly around the intake manifold and vacuum lines) if your car tries to die when you find the vacuum leak then that is the point of the leak.You could have a cracked hose, or it may be a leak in your manifold gasket and once the car warms up and things expand the leak opens up and lets in too much air for the iacv to handle. A leak may have developed around your throttle body gasket too. Good luck man.

Oh and the correct way to set your idle (not to say anybody else's is wrong, but this is the factory set way to do it for hondas) is to unplug your iacv, then you'll turn the air bleed screw (it's on the throttle body if you're looking strait at it into the throught of the manifold. Do not mess with the throttle blade stop on the left side of the throttle body (again if you're looking directly at the throttle body the stop screw is on the side and it's what the cable part will hit to stop the throttle blade from closing too far). With the iacv unplugged turn the air bleed screw in to lower the idle, or out to raise the idle. This air bleed screw lets air bypass your throttle blade when it's fully closed. You should get your car to barely run, your rpms should be around 500-550. If the car dies you've set it too low and need to back it off again and start her up once more. Once you've got this 'base' idle set, plug your iacv back in, unhook your battery negative lead (or a better way to do it is to take out the 'hazard' fuse from the underhood fuse block, it's a 15 amp fuse I believe) and let the car sit for about 10-20 seconds. This will reset your code that you set since you unplugged the iacv and ran the car. Now plug the fuse or battery lead back in and start her up. Your car should idle just fine and the idle should be around 750 rpms. It sounds complicated, but it's really not and it's pretty quick and easy to do.
Good luck man, hope you get her fixed!