MeLoN350

iTrader: (2)

I put in the pfc I bought off my buddy with the same mods, other than I'm running NS, and he had an apexi single. Started the car the first time and the idle was fluctuating between about 1800-2300. Let it run for a while and slowly worked its way down to about 800-900. Shut it off, went inside. Started it back up and it just idled smoothly at 2000, and the throttle had a horrible hesitation revving it up. I can uplug the ISC and it idles great at 800. I can hear the air going through it even, the PFC must be just opening the solenoid all the way. Any ideas? I cut the wires in the harness, and the idle on the PFC is set to 850, 950, and 1000. I have tried changing them also, but it has no effect. I have driven it today and other than not having the computer controlling the idle, it is running great and has more power than ever.

Thanks,

Nick

cewrx7r1

iTrader: (2)

The engine is getting too much air at idle, and thus the ISC can not be closed to reduce rpms. Reduce the idle air flow through the throttle body. Most PFC owners have experienced this. Rarely it might be a loose hose.

MeLoN350

iTrader: (2)

Do you know if it takes a little while for it to learn and bring the idle down or anything. I tried adjusting the Idle screw and I had it all the way in and it was still to high, I turned it 1 or 2 turns out, didn't change anything. When I unplugged the soleniod it stalled because it was not getting enough air. I had to open it up about another turn to make it idle at 800 without the ISC, so there are no vacuum leaks and the idle was turned down plenty far for the solenoid to control the idle.

Nick

cewrx7r1

iTrader: (2)

For the PFC to control the idle , it uses the ISC for air flow, and fuel along with the O2 sensor output to get the correct AFR. The varible timing is optional with the PFC.

In order to be able to increase or decrease air flow, it has to keep the ISV partially open. If closed was the norm, then it could not reduce air since the valve is already at it's minimun point. That is why the engine stalled when you pulled the ISC connector.

The ideal point if all was working correctly, would be for the ISC to be at the midpoint of it's operation, and the same for the varible timing and fuel correction. Thus the PFC could increase or decrease any of these parameters and smoothly control the idle. If something happens that requires a parameter to be adjusted outside of it's operational range, then the idle becomes cyclic as you are experiening.

Usually it is too much air. There are two idle adjustments for a fully warmed up engine that affects air. The throttle set screw which afects the opening of the primary throttle plates and is located on top. Then there is the air bleed screw located under the right/back rear of the throttle body, near the fuel vapor purge tank.

From your notes, you do not mention adjusting both!


If your O2 sensor control is on and the O2 sensor is hosed, this affects idle fuel delivery.

If the TPS is bad or out of adjustment, this also affects idle fuel.

A lose hose can also cause too much air.

Have fun finding the problem that Mazda has created!

Modern automotive electonics are great when they work, but are hell when they malfunction.

MeLoN350

iTrader: (2)

I didn't think the 02 would be needed and I don't really have one hooked up. I have a Greddy a/f gauge and it has an output to hook up to the factory o2, but the guage is not working correctly and it doesn't show anything on the sensor check screen. So I disabled the o2 feedback, thinking it would be fine, as I never ran one with my factory ecu. I'll fix that and see what happens. No, I have never adjusted the second idle screw, I have always used the main one. I'll have to look for it, it isn't the one that is used for the hot wax rod is it?

Thanks,

Nick

cewrx7r1

iTrader: (2)

If you have the O2 control turned off, then do not worry about the sensor.

The hot wax rod is not used in conjuntion with the air bleed screw but the screw is near it. I did not memtioned the cold start system in my prior post and do not plan to do detail it. It is used below about 140F to open the throttle plates a little, add more fuel, and also add more air the the AWS solenoid. These are easy to bypass(disable) for normal warm engine testing.

to_slow

iTrader: (3)

Man i have the same problem how did you fix it ? let me know .
Thanks Dan

MeLoN350

iTrader: (2)

I haven't, just adjusted my idle with the idle screw under the TB elbow to 800 rpm. Works fine for me so far, put about a 1000miles on it this way, the only problem is sometimes if you rev it up it will drop down to like 500 and then come back up.

Nick

to_slow

iTrader: (3)

Thanks