Hi all
Mx5 na 1993 1.6.
Hoping for some wisdom from you kind people.
My car doesn’t run right, high idle once warm. Base idle is fine.
Have checked for air leaks without finding anything.
I am trying to read the codes see what is there, but I have just realised I have no check engine light on ignition on so I can’t.
Before I pull the dash checking bulbs.
My car starts off a button. When I bought it it was like this, I turn ignition on with the key to ‘on’ but then have a start button that bypasses the ignition switch and is wired direct to the starter with permenant power. The starter will turn on this button even with the key not in the car so is a permanent live. but obvs doesn’t start as ignition not on.
Would this stop the check engine light coming on?
Tia
Nic
No NA UK MX-5 or JDM Eunos Roadster has a check engine light. American market Miata did. I assume you have a UK or JDM car.
With regards your high idle speed, have you looked at the idle air control valve under the throttle body? Disconnect the electrical connection and check the resistance across it.
Thanks Robbie
It’s a uk car.
Am I right in saying the read the codes by bridging terminals in the diag port and count the flashes doesnt work on uk spec cars then?
No I’ve not checked valve as yet, very new to these cars so will look there next, thought I would start with codes if in deed it was possible too.
Thanks for the info, I will report back once checked the valve.
Nic
Absolute legend.
Thankyou, have ordered.
Nic
So I ordered the diag tool. No codes.
Replaced all coolant pipes today as had a coloured set I was meaning to put on. At the same time removed throttle body, was pretty clean but now very clean.
Checked resistance across the idle valve and it was at 12. Which I think is fine?
With everything removed took all vac lines off, all in good nick, blew through with no leaks.
Warmed it up to get new coolant through until fan kicked in and set the base idle at just under 1k.
Then went for a drive. With a bit of spirited driving for 10 minutes idle back up to about 1.5k! Same with clutch in or out.
Any ideas?
That resistance reading of 12, can you confirm 12 what? Ohms or Kilohms? Also, since you’re mentioned it, have you checked the clutch switch? Does it go in and out and if so, does it should continuity and open when the clutch is pressed and released? I think that diagnosis kit that you got explains the switch test function, this checks the clutch switch.
I am by no means great with electrics but the reading was in Kohms. I was unsure so just stripped and rechecked and unless multi meter is set to 20k I get no reading at all on 20 or 2000.
Does this mean it’s fubared?
I need to get thinner leads to probe the clutch switch so may report back once I have some.
Pretty sure that 12 kilohms means that it’s FUBAR. Should be something like 18 ohms from memory, probably less.
I’m very confused. Was just looking at replacements and none of them seem to look like what I have in the car.
The 1.6 93 looks like a section that bolts underneath the throttle body, this throttle body and iac look like nothing I can find online.
Very much learning on these cars, but does mine look right?
Your help is very much appreciated.
That looks right, 1.8 ones are different.
Thanks. I’ve been researching. Looks like they changed in 1994 so mine is the proper early one at a 93.
I have found a repair video so will see what I can do, otherwise source a replacement.
Thanks for all your help Robbie.
Give this a read. Lot of good information. Looks like the ISCV should be 12 ohms so I would check you are reading the meter correctly.
Good luck.
D
https://www.miata.net/garage/isc.html
Hi all that helped.
Finally sorted.
It was the icv. I attempted a fix and did manage to trace the wire back to get 12ohms, but whilst doing so got a replacement with throttle body for £35 which was a good unit.
Thankyou for your help.
