Turning here to help diagnose an intermittent issue. Has happened twice. About a month ago daughter said the 1999 Miata w/2000 Miata engine wit 100k on engine would go over 2k rev and idled like crap. After sitting a while it ran normal. I looked at it and didn't see anything wrong, ran fine. Today with both of us autocrossing it, she taking it out on the last run and it does it again, this time I see at idle it surges a bit and won't rev past 2k. We let it sit while we change the tires back to the street tires, start it up and it runs fine again. Now know it seems to be heat related issue. I think coil pack but want some insight from other that might have seen this before.
I was going to guess a bad ground?
Joey
Agreed, check your grounds. I had similar intermittent difficulty recently due to a burnt out ground between the engine and chassis. There are many other possible causes, but this one takes a few seconds to check.
Now I have someplace to start. Thanks guys.
Just now used to fround issues on the Miata. A constant issue on the Opel GT and MG but Miata's generally just work until a part wears out.
Jay_W
Dork
3/23/12 12:12 p.m.
Bad grounds can do all manner of evil things. Ignition coils aren't the greatest but easy to diagnose, pull teh plugs and lay em on the valver cover, unplug the injectors, and turn the engine over. if you see anything other than bright bluse snappy sparks, you need ignition coil/igniter/wires. I don't think this is the case with your issue, as it wouldn'[t be intermittent. It'd be a full time problem. I'm gonna go with loose/bad ground. ALTHOUGH... this does sound very similar to when a bad TPS ruined one of my weekends awhile back. One minute it'd run fine, the next it'd stall and die and moan and groan and carry one. Easy to diagnose, pull the plug and get a ohmeter on the output pins and slowly open the the throttle and look for a nice smooth change in resistance. Mine had a loose chunk of variac rattling around in it, causing all sorts of havoc.
