First; Thanks for the tip on vintage rx 3forum. second I cant get to open for me. third I have had the carb on my 74 RX3 rebuilt changed coils set the timing with a light, blown out the gas lines and new filters fore and aft, It will not run onNKG plugs had to use champions, does not idle under 15K rpm, fuel pump is recent, at highway speed it runs fairly well but does backfire and miss. I am open to any and all ideas. it shows 78K on the clock. Bob

 

I would check for intake vacuum leaks to start with.

 

I assume you mean it won't idle under 1.5K, right? Idling at 15K is a bit excessive.

You replaced the coils, but how about the ignitors? A dying leading ignitor can cause all sorts of funky problems (as I found out recently), including rough idle. You could try running the leading plugs off the trailing ignition and see if it gets better (remember to advance the timing if you try this). Vacuum leaks, as RX3SP suggested, could also be the culprit.

 

No igniters just points, do have a spare RX7 dizzy tho. Bob

 

You're skipping all the basics first and that's what bite alot of people in the ***. First off, do a compression test. Disconnect your ignition system and put your compression tester in leading one and put the throttle wide open and crank the engine at least 3-4 crank cycles and note that. Do the same with the rear leading and compare the two. You should have somewhere between 75-100 psi in both front and rear and should not have large differences between the two. If that checks out then make sure you are getting spark on all 4 spark plugs and double check that all the spark plug wires are on the right location on the cap and plugs. Double check your timing. If all those things are good then you either have some large vacuum leak like mentioned already or your idle circuit is bad or not adjusted correctly. Good luck.