2002 Hyundai Elantra Hyundai Elantra Rough Idle - IAC, Coil

What is the proper method to test a coil?

Thanks.

Last night I worked some on the car. I changed spark plugs and plug wires. I also removed the IAC and tried cleaning it. I used some carb cleaner, Q-tips, and a towel to clean it out.

I put it all back together and started the car. There is no longer any arching going on, and the engine is running much smoother. It had a pretty nasty shake to it before. As far as the surging rpms at idle, it is still present, but to a much lesser extent. The tack would sit right around 1500rpm and would fluxuate up and down about 100 rpm.

It still isn't idling smooth, and the idle rpm is still higher than it should be, but I'm not sure now that the cause could be. It could be that the IAC is bad, but it was just replaced 3 years ago and seems like it shouldn't be completely shot yet.

I did notice that there was not a gasket under the IAC when I removed it. I don't know if there is supposed to be a gasket or not, but there wasn't one.

Is it possible that there could be a vaccum leak? When the car is running, I can hear a light hissing sound under the engine coming from somewhere near the air intake/manifold.

Well, I took my carb cleaner and used it to search for the vacuum leak. There is indeed a leak at the base of the IAC. When I sprayed the area with carb cleaner, the RPMs of the engine increased.

I'm planning on removing the IAC and using some RTV gasket maker to seal the IAC to the intake manifold. The only problem I'm running into now is the top bolt holding on the IAC. The bolt has a hex head that I can't get a socket around because of the IAC plastic body. It also has a phillips head in it, but it is now stripped. It was close to being stripped when I started working on it, and when I tried to remove it, it stripped. Now I need to figure out how to get the bolt off. I'm going to try a 10mm wrench and see if that works. I'll pick up a bolt extraction kit as well in case the wrench doesn't work.

It is a pain in the rear end to know what is wrong but not be able to fix it due to something silly like a stripped bolt.