Michael McCann

Hi all,

I have a 2000 Civic EX 5 speed that I'm having some issues with. 180k miles.

About six months ago, I had some problems with stumbling and idling. I cleaned the IACv and no fix, then found that the distributor was leaking oil, so I replaced the distributor and everything was great. Idled perfectly around 500, drove fine for a while with the exception of being a little jerky on and off the throttle.

Then last week I moved up to South Carolina. I'm from Florida and my car pretty much never experiences freezing temperatures, maybe once or twice in the past six months. The car made the trip fine, then when I pulled into a parking lot (it was in the 20s at this point) my CEL came on. I scanned it right then and got P0505, which is a code I had back when the car was stumbling. Right after that the car idled high around 1600, and basically had no power and was very jittery and weak. I had to rev it high and slip the clutch a lot to get it home.

So I took off the IACv and it appeared still clean from the last time I cleaned it. Went ahead and ordered a new one after reading a lot about them going bad and causing these issues. The wiring harness for the IACv looked fine. Installed it today and went ahead and took a look at the coolant, since some came out when I changed the IACv, and I figured I'd need to bleed the system.

The resevoir was actually empty when the engine was cold, which seemed odd to me as I remember checking the fluids not (too) long ago. But I went ahead and added coolant to the filler neck (which didn't take a lot) and the resevoir and ran the engine for a bit. Some air bubbles definitely came out, but the coolant level kept trying to overflow in the filler neck after that, so I left it. And now the idle started surging between 1600 and 2000, somewhat intermittently. It'd stabilize around 1600 again, then I'd rev the engine and it'd fall back down and surge again.

I decided to drive the car around and see if the coolant just needed to circulate more, and eventually when I pulled over it threw a code and went straight to idling at 1600 in a weird, weak kind of way. Scanned the code, p0505 again. At this point the car started driving very weakly again, I barely got it home. So replacing the IACv apparently did nothing except maybe temporarily mess up the coolant.

Any thoughts on what to do next? Kind of at the end of my rope, I have to get to work next week and I'm not keen on spending more money throwing random fixes at the car. I'd try leaving the cap off the radiator and letting more bubbles come out, but it keeps wanting to overflow. No overheating issues btw. Could there be a leak at the intake since it's affecting power so dramatically? Why would this only happen after the car was warm for a while?

Thanks,
Mike

HondaPartsHero

Michael McCann

I understand the "check for vacuum leaks" part, but is there a better way to do this than just spraying cleaner everywhere, and is there something specific I should be targeting? And are there any other things that could be wrong? The reason I'm asking is because this happened all of the sudden, and I don't understand how a vacuum leak could happen like that.

chrysler kid

My car had a coolant hose crack directly under the iacv. The Iacv wasn't getting the coolant it needed to keep it at engine operating temperature and it would cause the engine to miss and stumble.

Remove the air intake tube and inspect the radiator hoses right under the iacv and the main radiator hose fittings at the engine right before the intake manifold

Michael McCann

Well I feel quite dumb! My problem was solved rather easily. I stumbled across this video:


And my problem was this exact one. This vacuum tube likes to come undone. I'll be putting a more secure clip on it in the future. It's a pretty easy thing to miss as it's kind of on the underside of the TB, and the tube just hangs off to the side when it's unplugged. Thanks to all for the advice, I'm glad I was able to get this resolved without any more trouble.