Valkyrie

And the FSM says….?

Just FYI, if you’re following the US-spec FSM, the coils in JDM cars were relocated after 1995…

philiprivers

FSM says between 9.6ohms and 16ohms for the leading coils. So it is reading within spec.

philiprivers

Just tested the primary coil winding (plug for the coil) and I have 0 ohms. FSM spec is less than 1ohm but obviously not 0 ohms right?

Valkyrie

Test your spark!
Test compression when you can.


When I bought my car, which was basically a parts car, the engine ran like ****. I tested all sorts of things (including testing and swapping coils) only to realize I had a loose ground. Once I tightened it up, it ran perfectly.

philiprivers

swapped the leading coil with a known good one and fired the car up. Issue was still present. But I noticed something weird when I hold the throttle around 1300rpm the air pump turns on and I have 400mmHg of vacuum yay! But when I let my foot off the gas slightly rpm’s drop to 600 and it reads +36mmHg or .05kg/cm2. Why would the air pump be causing my vacuum to change so drastically. Something else is my PAC (Port Air Control) would turn off then turn on then turn off and it was causing my car to sound like it had a crazy bridgeport and I know that isn’t supposed to do that.

philiprivers

Valkyrie

My car doesn’t have an air pump, emissions, rats nest, or stock twins, so this is above my pay grade…

FDAUTO

iTrader: (4)

wow... things just got weird. none of that makes sense. unless the aiv has failed in some extremely odd way, the condition you have doesn't really make sense. sorry homie but i think your next may be to pull the uim and start poking around. unless this whole thing is some strange electrical issue that is throwing the the map sensor for a loop and associating it with the air pump. or maybe this a new way that indicates a failed power fc. they have been known to do some strange things but i've never heard of this one before. would you happen to have a stock ecu or another power fc to try?

did you try manually controlling the vacuum on the map sensor yet to see what that would do?

scotty305

iTrader: (2)

Those MAP sensor readings could be a signal problem like a broken vacuum line to the MAP sensor, damaged sensor, wiring harness problem, or even a problem with the ECU input circuit. Or it could be a real reading and the engine might not be pulling normal vacuum. Have you got a cheap mechanical vacuum/boost gauge you can use as a second reference? It doesn't need to be permanently installed in the car, just run some vacuum line through the passenger window and temporarily set the gauge somewhere near the PowerFC screen so you can compare the two.

If the mechanical vacuum gauge matches your ECU's MAP reading, you can quit getting side-tracked by that and find the reason why the engine isn't pulling vacuum.

philiprivers

Finally some good news! Disabled o2 feedback and I’m idling around 900-1000 and with 390-410mmHg and the car sounds great. Now occasionally my rpms will drop and the air pump with turn off and then on for a split second and the car will run like **** and then it’ll be back to normal.

philiprivers

https://youtube.com/shorts/hRygO-ycijU?feature=share

video of rpm’s and vacuum at idle

philiprivers

earlier in the thread I talked about getting a known good MAP sensor and it did the exact same thing showed the same numbers, did the same bench mark vacuum tests (me sucking air into the end of the hose)

philiprivers

As the car would idle and it warmed up the car was beginning to run worse but I don’t know how it’s supposed to run with o2 feedback disabled. The rpms were loping but the air pump was on the entire time and I couldn’t hear any clicking which I assume is relays giving power to certain things. Any help or ideas for this SUPER weird problem would be greatly appreciated

Valkyrie

It sounds perfect at first, and then it starts dumping 50% more fuel into the engine for some reason.
You aren't confusing your air pump and your air conditioning compressor, right?

Since it's insanely hot in Japan right now, I assume you have your A/C on.
I'm almost wondering if maybe your PowerFC's A/C-ON idle settings aren't coping with the demand from your compressor.

What happens if you turn your A/C and blowers off?

What happens if you unplug your air pump?

My recall is a but fuzzy about how the secondary air injection on the FD works, but maybe you've got an emissions control valve sticking open?
I almost wonder if extra air from the air pump being forced into the manifold isn't causing your vacuum to read low (unless it's just the extra fuel causing your RPMs to drop that is the cause of this).
Because it runs perfectly until something is causing the vacuum to decrease and fuel to increase.

philiprivers

what I have been using to see if my air pump is running or not is my APR (Air Pump Relay) on the Sensor Check screen. I have had my A/C and blowers off the entire time unless I turn them on to see if the car changes it’s idle more than it should.
Last week I unplugged my air pump and started it and I couldn’t get the car to start, I flooded it. I have read the car should start with the air pump unplugged.

Valkyrie

Might be time to consider trucking it to your nearest rotary specialist (or at least a tuning shop with RE experience). I wouldn’t even bother with a Mazda dealer, unless they have someone who can actually work on FDs (they do exist).

philiprivers

unfortunately there is no tuning shop or rotary mechanic close to me. I do think I can figure it out after narrowing it down to the emissions system. The car is drivable now after disabling o2 feedback. The throttle is slow to respond but I can drive it now so that’s a very good sign. I’m pretty stoked at my first positive improvement throughout this entire ordeal.

philiprivers

SOLVED! Kind of. I unplugged my air pump with o2 feedback disabled and the car is running better than ever. Don’t know why it was doing what it did, but thank you all for the helpful advice. I couldn’t have done it without you guys!

FDAUTO

iTrader: (4)

I don't know about this one.... you may have just masked the real issue by doing this. May or may not come back in a different way. Definitely be happy its problem "solved" but don't be surprised if it comes back as something else later.

Also be mindful you're gonna have to plug in the air pump for jci whenever you're due

philiprivers

just had JCI completed maybe 2 months ago so I won’t have to complete it again. And part of me wants to just rip all of that **** out associated with the air pump. I just don’t know where I be living next and if I will need to have it pass emissions. 1100rpm 410-380mmHg and no surging idle. I’m happy with this.

FDAUTO

iTrader: (4)

Well damn even better lol just having passed really helps this whole thing. The only other place you'll really have to worry about emissions is somewhere in Europe if you end up there. If you come back to the states then you can just register it here in Florida regardless of where you end up and that won't be a concern ever again.

If you know of anyone in Europe at a place that you coukd possibly end up, ask if they do emissions testing as part of the registration process. If its a no then start pulling that stuff out if you don't intend on staying there

Valkyrie

You don't need an air pump to pass Japanese emissions standards unless your FD is one of the last few years. But you do need a special catalytic converter. I have heard you technically don't need the converter except for the visual inspection... The old standards that apply to most years of the FD for were quite lax.

FDAUTO

iTrader: (4)

Maybe it's different now or something but they definitely wanted me to have one for my 92 and my 99.... that and a stock cat. This was 10 years ago though 😅😅

Valkyrie

When you're buying a special "airpumpless" catalytic converter, you're really just paying for the papers.
You can't buy a used one, either, since the papers are specific to your chassis number.
If you have an airpump, you can install an aftermarket cat with no issue.