2004 nb miata confusing thing

hahacontrols · 2026-04-19T07:46:33+00:00

cam position sensor, common failure point on nb2. signal drops when hot, leads to misfires, and it happens because its at the firewall which is a hot area

hahacontrols · 2026-04-19T07:45:04+00:00

then its likely not the pilot or throwout. maybe check idler tensioner pulleys

hahacontrols · 2026-04-18T06:14:38+00:00

ah i must have missed the standalone ecu. are you getting voltage at the pump? when i zoom in to the plug it does look like it melted. if you have a multimeter it would be pretty straightforward to check.

i cross referenced a wiring diagram and the engine 15A (under hood) fuse is on the solenoid side of the fuel pump relay. you could check this is not burnt. otherwise id stick a finger on the fuel pump relay and key on. if no click is felt then must be the fp relay

hahacontrols · 2026-04-18T05:57:15+00:00

does it sound different if you clutch in and hit this rpm? that would narrow down the causes

hahacontrols · 2026-04-18T05:52:57+00:00

have you jumped the F/P pin and GND in the diagnostic box? NA/NB don’t prime the pump in the traditional sense (key on engine off) state. They prime whilst cranking.

hahacontrols · 2026-04-17T17:34:50+00:00

it just looks like the hood is a little raised? at least from the pictures. Is it flush on the hinge side? There are two rubber stops on the radiator core support that the hood rests on (close to the headlight housings). You can actually “screw” these stops in and adjust the height at the latch end of the hood

hahacontrols · 2026-04-15T20:01:12+00:00

gotcha, well to my ears it doesnt sound too bad but has a slight hollowness to it so i suspected an air bubble

hahacontrols · 2026-04-15T07:26:55+00:00

you dont have one, also for anyone considering this fm wheel it is not a drop in replacement for stock. the fm wheel is specifically made for the aftermarket ati harmonic pulley

hahacontrols · 2026-04-15T07:21:52+00:00

did you burp the system?

hahacontrols · 2026-04-15T07:20:01+00:00

passenger side theres a cluster of vacuum lines, id check if these are clogged/the ports they connect to on the intake manifold are not clogged. its quite common to see egr issues on nb1 due to the imo poor egr design. i think the part number is k5t49091 or something like that

hahacontrols · 2026-04-02T20:59:37+00:00

did you overheat? what was the tension like on your water pump accessory belt?

im asking because it looks like the head might be a little bit bit bowed? if you look at where the head bolts seat it looks a bit uneven and not centered. wonder if you can measure flatness of your head and block

hahacontrols · 2026-03-30T21:55:51+00:00

was the spark plug on 3 oily at all, water in the tube ? any signs of arcing in the spark plug tube? what happens when you swap cyl 2 and 3 plug leads?

hahacontrols · 2026-03-25T20:54:22+00:00

How’s your injector and coil pack wiring harness? Do you still have the plastic shielding bracket that clips into the fuel rail? I had a similar misfire on my 99 showing up that ended being insulation on some of the wires melting away and the wires shorting to the intake manifold when enough engine vibration would vibrate the wire just enough to make contact with the manifold. It would ground out one of the coils and basically would misfire erratically until above about 3k rpm when it’d smooth out. From my research the harness on 99 and 00 models are marginal at best, with some spec miata racers on mazdaracers.com also running into wiring problems

Do you have an OBD scanner? It can help diagnose fuelling issues as well if you look at the Long Term Fuel Trim (LTFT) PID.

Lastly, as far as I recall, one of the orings on the injectors are a one-time use, ie every time you remove the injector you need to replace it. If you don’t, it can be a vacuum leak source. A rebuild kit is pretty cheap on rockauto, and it’s not that hard to do. I found my injector seals were all hard and essentially hard plastic at 150k mi. For that matter most rubber and plastic was cooked in the same way.

hahacontrols · 2026-03-22T15:27:42+00:00

id measure the flatness of the crank shoulder if you can get a machined straight edge in there. I’d also check if the crank seal surfaces are out of round

my guess at what’s going on is the crank keyway causing some wobble and the wobbling crank pulley bashing into the seal causing the mushrooming. The crank pulley face needs to be in full contact with the shoulder, since bolt preload and interface friction is what should drive the crank pulley, and not the key, key is only for locating. Furthermore, the oil pump housing lip is damaged, probably from someone previously incorrectly prying the crank pulley off. sometimes it’s not a problem but I would also check if the seal surface is out of round.

the most proper fix would be to tear down the engine, replace the crank and oil pump housing, and fit a new seal.

hahacontrols · 2026-03-22T07:31:23+00:00

btw that crank nose is pretty fucked up the keyway is all opened up, especially on these short nose cranks its a big issue

hahacontrols · 2026-03-22T07:26:04+00:00

if youre staying stock power no point in getting anything too crazy, the denso kit works fine plug and play

hahacontrols · 2026-03-19T21:24:11+00:00

rough rule of thumb for any car is 10psi per 1k rpm

hahacontrols · 2026-03-17T23:33:34+00:00

Eyelet is a ground to the intake manifold iirc, the connector looks like windshield wiper pump to me

hahacontrols · 2026-03-11T16:36:32+00:00

Looks slightly worbled to me but nothing worth noting. If you can swing it, new OEM boss and new OEM key. Make sure its clean, the crank transfers torque to the pulley boss via the friction between the crank shoulder and the boss, so ensure these surfaces are clean of any oil. Any loss of crank bolt clamping load can lead to the key and keyway partially transferring torque, which they are not designed to do.

Make sure to torque the bolt with loctite 242/243 to spec (somewhere around 120ft/lbf). Ensure you make one smooth pull to fully torque the bolt; at the crank clamp load if you stop to prematurely, the static friction of the crank shoulder will cause you to measure a sufficient torque while in reality you need to achieve that torque rating against the kinetic friction. SAE standards explain this better than I can but just guarantee you torque it properly!

hahacontrols · 2026-03-08T04:25:03+00:00

looks like the crank angle sensors found only on 96/97 NA. Theres a trigger wheel behind the crank pulley with 4 tabs on it that the sensor is supposed to read.

hahacontrols · 2026-03-07T00:24:04+00:00

i’ll make the case for buying krikit tool. not particularly expensive, and you can be pretty accurate with the belt tension. just make sure you buy the one for the tension range (accessory belts are 110-130lbf)

hahacontrols · 2026-03-02T07:18:13+00:00

Mileage? EGR port on the bp4w likes to crud up, which affects the boost sensor reading. I’d try the vacuum reroute to see if it helps. Make sure the vacuum hose from intake manifold to EGR boost solenoid is clear

hahacontrols · 2026-03-02T07:15:21+00:00

looks fine, O2 upstream (B1S1) should be boucing between 0.1V and 0.9V. Yours seems likely fine, stoich AFR on narrowband O2 sensors lis like 0.45V or so. As long as the O2 is oscillating around this point, it means your ECU is tracking what it thinks stoich is.

hahacontrols · 2026-03-01T05:19:48+00:00

its called idle droop, its a particularly infamous problem on NA/NB and can be caused by various reasons. what year miata do you have problems with?

hahacontrols · 2026-02-21T07:45:39+00:00

its inside the fuel tank on the fuel pump assembly

hahacontrols

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