Miata won't run...

NYSpeed Automotive
1

Problem as it stands.

Car will start.
Will not idle. If kept above 2000 rpms will rev smoothly and holds rpms with ease.
If it drops below 2000 rpms the car falls flat and tries hard to stall, even when given full throttle.

I have replaced and/or checked all vacuum lines.
The big plastic plug on the back of the intake manifold is in place.
Same with the short line to the FPR and the cap for the cruise tap.

Replaced the AFM/02 sensor/PCV valve/Plugs/Wires

I have also checked my intake piping which is currently an elbow off the JR intake and one piece of straight 2.5 pipe

Cleared my codes. None returned.

I am stumped.
At this going rate I am going to pull the 1.6 for another or a 1.8

When I let off the throttle (above 2000 rpms) it make vacuum and then looses vacuum and fails as it misfires and stalls.

2

what year is the car

nice signature by the way

3

What were the codes before you cleared them? I would venture to say that changing the engine out is a little bit of overkill. I’d keep looking for vacuum leaks, maybe check the TPS. Check your fuel pressure & timing. There’s got to be a relatively simple explanation

4

did you have the engine out of this thing?

is the IACV plugged in?

5

sounds like the vane air meter to me … where ya live i can take a look im pretty good with mazda’s what yr and what motor 1.6 or 1.8?

6

2 options

IAC is stuck closed
EGR is stuck open

hit them both with a hammer, seriously

7

^ i was thinking the same thing, either EGR or IACV related. if niether of those it could be a TPS

8

do you have that tube hooked from the bottom of the throttle body to the intake

9

Weren’t you having an issue with the IAC prior on this?

Maybe something not connected back up possibly as well on the vaccum side.

10

sometimes depending on the connector it is easy to hook up a tps backwards

11

sounds like a mass air flow sensor if the miata even has one. dont they have the funny looking ones like the probes n older fords

12

i would definitely test the tps, I had issues with that on my civic and the symptoms were very similar.

13

you recently did a head gasket right?

14

Thanks for all the input.
16 hour shifts are not helping get around to working on this damn thing.
Every plug is connected to it connector.
I am going to just hit things with hammers.

It is a 93.

And I am only worried that it is an electrical issue
But I am just thinking I got another fucked AFM (new one enroute)
When I get some garage time I’ll post up another list of shit I checked.

15

ouch, good luck with it man

16

$10 for your miata :smiley:

17

if you unplug your afm. if it runs the same with it unplugged u have a bad one

18

i wouldnt say that , your fuel turn on/off switchis inside the airmeter its allows voltage when the flap goes off closed, if you think its the meter jump the 2 pins for fuel and it should run with the meter unplugged…

19

what happen to v8 swap?

20

am i to assume this means you have a JRSC on the car? if so your bypass valve could be stuck closed, such a condition will cause similar behavior as the engine is trying to idle on boost which is no good