Randomly drops in Idle and sometimes dies. OEM Coil Pack OHM's? CAS?
 

Alright I have been trying to install MS on my car and having an idle issue.

After scaring myself I went back to stock until I could make some progress.

Today was the first day I really drove it and during the day it seemed fine, tonight however I found an issue...

Randomly (I can not reproduce it I keep trying to) it will suddenly drop to 500 RPM with the clutch in and sometimes die.
I thought it was because I needed to readjust the Idle Air Screw (I had been messing with closing it while working with the MS), so I did and it came back, so I did it again... and it came back again just now.

But after the first time the car would again randomly (I also could not reproduce this which I also tried too) buck and shake refusing to move while in gear but fine out of gear and then it would go away.

I checked the plug wires and one was popped up and clicked back down and while it has not done it again it did die again (This was also at the same time I adjusted the idle air screw for a third time) it never bucked.


I have come across some threads that say common issues are either coil packs or CAS.
I have one more set of coil packs I know works but I would like to OHM test these if I can whats the factory acceptable specs on the coils? (If possible)

As for the CAS, Where is this? I take it as a Crank Angle Sensor? or Cam Angle Sensor? or am I way off?

Hopefully this will point me to the issue I was having with my MS too... or just show me something I hurt while playing with MS.

Thanks!

2000 Miata, Not Boosted.

What MS are you running? Are you running open or closed loop idle control? Try unplugging the IAC and see if you have the same problem. IF you do, then it is probably the MS settings.

Sorry for the confusion but the MS is off I went back to stock to see if it was a vacuum leak issue like a few brought up.

This is on the stock ECU right now.

So today I pulled the codes and got:
P0113
P0118
P0123
P1141

So I cleared them and they came back shortly.

So I replaced the Coolant Sensor, IAT Sensor, MAF and the whole Throttle Body with both the TPS and IAC sensors.

Made it a block and the car stalled again.

The gentleman I get all my Miata parts from was out of ECU's for 99-00, but he believe the ECU was the problem.

All those codes mean High Out put except for 1141 I believe is MAF related. All pieces have been replaced so I am not sure what to make of it here.

With all those parts replaced I find myself wondering just what could be the issue but this was not an issue before I started MS so either wiring is the issue for some reason (less likely in my opinion), the Stock ECU got damaged some how (More likely) or there is another issue I am not finding.

Mine's a 95 but has a similar problem. Randomly, instantly dies and will not restart, just cranks like there is no spark, wait a few hours or days and it starts and runs fine. Not heat related because one time it started and ran for 10 seconds, then just cranks. After 2 weeks of checking wires and pulling parts, I'm 80% sure it's the CAS, looking for a replacement now (cheapest is on Amazon $291).

Well I damaged my laptop last week and have been waiting on a replacement screen which should be here tomorrow.

But while I have not checked codes again the car has not had any issues since the last clear after new parts.

I am not sure what to make of it but tomorrow I should finally have some time again and I will check the codes again.
But maybe the problem was resolved by the replacement parts.

Either way maybe this friday I can shoot for Megasquirt trials again.

They go for about $30 on ebay. Sometimes cheaper.

Have you looked into fuel pressure? My pressure regulator craped out on me giving the same issues as you listed.

when was the last time you changed the fuel filter?

Honestly after clearing the codes (after swapping out the above mentioned parts) the car has been just fine.

I am under the impression it was the TPS or sim on the way out before MS and it finally did when I put in MS.

Everything seems fine now I will be trying MS again this weekend.