You cleaned off the sealant on your throttle butterfly, so now you have a leak your car is trying to deal with.
You cleaned off the sealant on your throttle butterfly, so now you have a leak your car is trying to deal with.
Crap. It look like the cleaner didn't affect the sealant and it's still present, so I guess I just cleaned up enough to affect the way it seals?
New TB/butterfly time or is there a way to fix it?
http://forum.miata.net/vb/showthread.php?t=446148&highlight=high+idle
Probably what Keith said. But just in case you might check the above linkie.
It's fairly common for us to get a call from people who cleaned up their "dirty" TB and now have a high idle. Sounds like you didn't get it all, usually the IAC isn't able to bring the idle down.
I've seen it fixed with paint. Just close the throttle and shoot a little bit of rattlecan paint around the edge of the butterfly. Basically, paint it shut. Then crack it free when it's dry and voila.
By the way, if you ever want to diagnose a potential problem with the IAC, just unplug it. Does it change?
I'll check the stuff mentioned in the link - I know the TB isn't held open by the throttle cable (it does hit the idle stop) but if the 1.8L also have the air valve mentioned in the link, that might be part of the problem.
The throttle body was extremely gunked up when I looked at it and most likely didn't seal right at that point, but there's a good chance that the spray-on cleaner might have dissolved the sealant, even though I used the proper throttle body/carb cleaner. Oh well.
I'll unplug the IAC and see if that makes any difference to the way it idles, then will report back.
BTW, apart from the paint fix, how much does a good used throttle body run at?
FM Salvage has 'em for $30.
I had another look at the throttle body and it very much looked like the throttle plate wasn't closing properly when I was trying the "hold a flashlight behind it" test. The coating on the plate still seems to be there, so my theory is that someone tried to tweaked the idle using the stop screw. When I de-gunked the TB I removed a 'ring' of deposits in the actual throttle body that probably had been enough to almost mask the fact the throttle plate wouldn't close far enough. Which explains why the engine revs would drop to about 1k rpm, stay there for a few seconds and then drop to ~850 before I cleaned the TB.
Anyway, long story short - I tweaked the throttle stop screw slightly (probably 1/3 turn) and the idle now drops all the way to 850 straight away. Phew.
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