Intermittent Misfire

[rabbattackk]

Hey everyone! Since this is my first project car I'm still learning. I purchased an early m20 and a 1987 e30 sedan separate. I have installed cooling/wiring/etc and got it running and driving. The compression on all cylinders is between 160-175. I have installed and gapped new spark plugs and fresh fuel. When I start the car and the engine is cold it idles nicely and sounds good but after 2/3 minutes of idle it develops a misfire that isn't every revolution but like every 3rd. What could cause this/what should I test before throwing too much money into it.

[tomstin]

Check all the temperature sensors, here is a good reference on idle issues http://www.verrill.com/car/e30_idlefaq.shtml

Next, check your crank position sensor(s). Depending on which engine, there may be one (i) or two (e).

[Gregs///M]

Check the condition of your cap and rotor and ignition system. If all looks good, a failing AFM can cause this condition. So can a failing CPS.