[FIXED] 97 honda civic idle surging up and down

hello fellow mechanics, my issue with my honda civic is that after i replaced the timing belt, water pump and oil pump, and drained the coolant, and after putting everything back, my civic began to have idle issues. idling up and down at idle. something it never did before. can you guys help me by enumerating some steps that i can take in order to solve my issue so that i can share with other mechanics here how you guys helped me solve the problem. thanks

Welcome I'm moving your topic to the repair section. Also try to post as much info as possible.

Welcome to the forum, Okay if I remember this era of Honda PGFI engines used MAP for fueling, my first check would be to be 100% sure you don't have any vacuum hoses disconnected or any other potential vacuum leak.

Classic symptom of low coolant, causing the fast idle thermo valve to stay open. That causes a high idle, which the PCM then tries to control by taking injector pulse away. This is the source of the idle surging.

I'm not saying you didn't fill the cooling system, or that there are leaks, only that air pockets in the system are common after big cooling system repairs like a water pump. Even when using a vacuum filler, this kind of thing still happens.

First thing to check is the coolant level, and that the hoses to the fast idle valve are there/not collapsed/not kinked. This SD video is definitely worth watching:

good tip tyler that brought to mind the ol boxers we gotta raise the front of vehicle a bit on subys to get those air pockets out I was just brushing up on idle controls in sixth edition

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I use a funnel like this to aid in air bleeding the coolant system after any kind of service that requires a refill.

thank you tyler. that was exactly the problem. I removed the fast idle thermo valve and cleaned it. the head that goes inside of the magnet was stuck. it didn't hardly move. so i had to clean it with carburator cleaner. put it back and it worked like a charm. thanks to your insight. I thank you and appreciate what you did for me. thanks tyler.
I'm trying to send you some photos, but I don't know how to send them from my mac. anyway you did good tyler thanks again.


eugene

Glad to hear it worked out! The dual valve setup used on this generation of Honda engines wasn't great, and prone to problems as you found out. :lol: I'm not sure, but it sounds like you actually cleaned the main IAC valve? If that valve was stuck, it can cause a high idle as well.

Have you tried uploading the photos directly to the forums? If not, you can email me at wrenchturnsyou@gmail.com.

Tyler let me know when you receive the pictures

Because of Tyler, as scanner danner would say, THIS IS A FIX. car is done, finito. thats all because of you tyler thanks buddy.

Got the pictures. Yeah, that's the main IAC. But hey, a fix is a fix! As I like to say, if the car is happy, I'm happy.

Those barrel type IAC valves used by Honda and Toyota are known for exactly this kind of issue. I've had pretty good luck getting them unstuck temporarily by tapping on the housing with a screwdriver. :lol: