Replaced radiator & hoses, all hell broke loose! (2000 EJ8 -- P0505 and noise)

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1 week 3 days ago - 1 week 3 days ago #203846 by grievre
Imgur cut my video off at one minute but I'll link it anyway since it shows off the noise and behavior I'm talking about: imgur.com/a/DH8FXj3

I finally finished replacing the radiator, thermostat, overflow tank and heater hoses on my 2000 civic EX (non-ABS automatic, 2-door coupe, 260k miles). No leaks!

First, some stuff from before this repair: The car has had a hunting idle issue for the past year at least, but it was never bad enough to make me do anything about it and it never set a code. A month or two ago I noticed a burning plastic or burning electronics smell that was detectable both under the hood and in the cabin, but it went away after a few days. I noticed some noise from the accessories at this time too but it wasn't so bad

I bled the coolant system while it was still jacked up for a bit. While bleeding the coolant system I noticed a rather distinct metal-on-metal squeak coming from the engine near the driver side (in the video). This noise is different than the one I heard before.

After getting it off jack stands after a few weeks of sitting in my garage, I take it on a short set of errands around town and see a check engine light. I take it to shell to use their self-serve scanner thingy and I get back a P0505 (Idle air control system malfunction). Driving home I notice some surging and bucking when applying slight throttle.

I read up on P0505 and I find out that, of course, it can be caused by air in the cooling system. While shopping for a new cap and hoses for the reservoir tank I notice in the parts drawing that there's some kind of seal on the cap. I go down and check and sure enough it's missing. I figure I might as well bleed the cooling system some more anyway since it doesn't cost anything but my time.

With my car now parked facing uphill on my somewhat steep driveway, I start bleeding the cooling system again and only now notice the bucking at partial throttle that you can see/hear in the video I linked. I also notice that if you rev the engine it dips WAY down before coming back up to a sensible idle speed.

I bleed the cooling system for a good half hour but even after that point there are still a few very small bubbles coming up. The overflow cap seal is still missing so I figure I'll wait until I have that in place and try bleeding again.

Now, I'm wondering if I broke something by removing the airbox and moving the intake hose around while working on the cooling system. I did have it bungee corded to the hood for a while. I re-checked and I didn't see any electrical connections or hoses loose.

The other thing I'm wondering: The car's been in my closed garage for a good 2 or 3 weeks and the temperature in the area has been dropping sharply for the past month. Could these problems have showed up because the car got a lot colder than it has been for the past few months?

Edit: more details
May or may not be relevant:
* I also changed the transmission fluid at the same time, dunno how that could affect it but figure I should include it anyway.
* I have noticed somewhat worse gas mileage recently but had just chalked it up to using the AC a lot
Last edit: 1 week 3 days ago by grievre.

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1 week 2 days ago #203856 by grievre
One thing I forgot to mention: It seems to stay at fast idle (~1000-1500) when warmed up now.

I drove the car again today and it's actually a bit hard to replicate the rapid oscillation you can see in the video. I could only get it to happen when parking after a 15 minute drive and it only appeared when I turned the AC off. When I got back to my car an hour later it was gone and didn't reappear, even after a much longer drive home.

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6 days 19 hours ago #203874 by grievre
Turns out one of the coolant hoses I didn't replace sprung a leak (no surprise). Will revisit after I've replaced the rest of them.

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6 days 2 hours ago #203876 by college man
Glad your making progress.

Believe it or not Iam trying to help you.

Proud to be Eric The Car Guy Certified.

Over 10,000 posts strong.

Mobil1 New Jersey highway tested everyday.

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5 days 18 hours ago #203878 by grievre
I also took the intake duct off and noticed a crack in it. I'm trying to figure out how a crack in the intake duct would cause an issue in a car with a MAP sensor since they do list it as a potential cause for P0505.

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