I have a 99 lx civic. I have done a full tune up from spark plugs to dis rotor. Fuel system treatment and pcv valve and fuel filter. I also cleaned the iacv. I noticed prob after a months after I did all that the car had this weird shutter at idle. Like a misfire. It wouldn't due or anything serious but when warmed up and idle at stop light it would shutter every 30 sec to a minute. Not sure if anyone has had the same issue plz get back to me. Oh and also it runs perfectly fine while driving only at idle it happens.

 

Check / adjust the valves.

 

Previous owner had already done it plus I don't hear any ticking from head. Sounds quiet. It just barley started doing it 6 months after owning it. I read that the distributor could be going bad. How do I go about checking it.

 

How many miles ago?

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Doesn't indicate wether or not the valves are adjusted correctly

Read this: Part 1 -How to Test the Igniter, Ignition Coil Accord, Civic, CRV, and Odyssey (pages 1-5)

Do a power balance (drop) test. Instead of pulling spark plug wires ..pull fuel injector connectors one at time and listen for idle to drop or stay the same. If it stays the same there is an issue. Check ignition timing with timing light.

Try turning headlights or a/c on while it's idling and see if it does what you described initiially.