hey all,

well four months ago my timing belt on my 4th gen prelude SI broke. It bent all 16 valves, so I replaced them all, and did the valve seals, oil seals, headgasket, etc. Since I had the head off.

Well, I put it all together a few days ago and now I am having a messed up idle. When I start the car the idle jumps up to 2k. Then when it gets warmed up it will drop to 1k and fluctuate between 1200-1500rpm... over and over and over.

I checked for the obvious (vacuum leak, air in coolant) and couldn't find anything that worked. I got rid of all the air in the cooling system and still the same problem. It was then brought to my attention that the headgasket mating area is supposed to be clean enough to eat off of. Now at the time that I did the headgasket I didn't know this, but still it was relatively clean.

Right now I'm debating if I should just do the whole thing over again, or if a bad headgasket job could even cause an idle problem. Or if there is anyting else to look at at There are no CEL lights, so I'm assuming that none of the sensors went bad. But a few people have suggested that maybe it's my map sensor.

Also, I used silicone hose from silicone techniques, and for some of the cooling lines I used a slightly smaller (1-2mm) hose for the EACV, and Fast Idle..

thanks
alan

 

The rule usually says that the head gasket mating surface should be extremely clean, but a slightly less than clean surface should not be enough to really screw things up for you.

There could have been many different things wrong with your motor as I read through your post, but here's step 1.

PLEASE do yourself favor and get rid of that garbage silicone hose. I've see it foul up so many motors the first thing our techs do when servicing cars is rip it out and replace it. This stuff does not work and only adds to the "rice effect."

Chances are once you've replaces these hoses your car will run much better. If it does not work, feel free to post back.

Good Luck and happy wrenching!

 

thanks, I was about to pull the head, but i was 100% sure it wasn't my problem. tomorrow morning i'm going to put it back together. I've already went back to stock hoses for all the coolant hoses to.

out of curiousity, why are the silicone hoses no good?

I bought them just for the silicone factor (I even just bought black) I guess I was swayed by silicone techniques.

as far as my idling problem, I'm guessing it might be a bad sensor or something dumb like that. Or maybe even the gaskets that sandwich the butterfly valve plate.