Idle started surging. No event took place. No new noise. Just out of no where. When I start the car it surges to 3k. Then it backs off and this happens indefinitely.

 

unplug the iac and see if it stops

 

Unplugged. Started car. Rpms shoot to 2400 rather than 3k Then hunts/surges between 1100 and 2200. So it’s still happening just not as high in the rpm range

what is the wax rod. I am not sure where to locate. But read it’s common for a surging issue.

ty

also can this be power fc related. Like its in a learning function. I think this happened before. Did it for 15 minutes. Then self corrected. This is more persistent

 

@DaleClark

any thoughts on this? I am bummed. I just finished auto tuning and the car is running better than ever. Obviously besides this. I loaded my final auto tuned map. Went for a 30 minute ride to run errands. I babied it around town. About a block from my house on way home it started. No event occurred to start it.

This has happened before. Last year I was out for a spin and it happened. For whatever reason it went away just as quickly as it came.

couple topics:

- could it be some sort of learn function with the power fc? Is there an idle reset function that could be triggering ?

- As a test, I unplugged the iac. Started the car and it still does it. Is this a good test? If it’s stuck maybe unplugging the wire connector simply left it stuck so the test isn’t a good one? I don’t know if that makes sense. Thoughts on that?

- what about the thermo wax? I don’t know anything about this. But since it happened before and happened again maybe something with that? If this is a reasonable topic I can search it up. If it makes sense.

- I also read about the clutch switch. It seems the springs go on them. But I pushed my clutch in and tested the switch with my finger and all seems good with it. It pops right out. Can’t see how a clutch switch would lead to this sort of surging and bouncing

- if it was a vacuum leak then why would it happen last year then come back. Also why would I have solid boost.

I think the important caveat is that this happened last year. Went away almost immediately. And this time it came back but isn’t going away. It makes me think of some sort of hardware issue that finally went. Thinking along the lines of a sensor issue that finally went. So I can’t help but think it’s the iac.

 

Does anyone know if it’s the IAC and I unplugged it. But it didn’t change anything. Does that rule out the IAC?

my thinking is that it is a sensor that moves a mechanical plunger like thing. If that plunger is stuck or not fully moving due to carbon etc. wouldn’t that mean unplugging wouldn’t rule it out.

i am not sure if that makes sense. Hopefully someone chimes in to answer


so far I adjusted the tps a very small amount and reinitialized the power fc. Then loaded my map back. It didn’t do a darn thing. I think bc the car fails to get to idle to even do the learning process. Make sense ?

 

The ISC solenoid in conjunction with O2 FB conrols idle.

If you had the Apexi PFC ecu it would be easy to diagnosis.

 

My understanding is the Power Fc does not use the O2 sensor (except , perhaps, in some advanced diagnosis programs.)

A vacuum leak will cause the Power FC to hunt considerable and yes it may self adjust, as you have experienced.

But there may be limits to the parameters for self adjustment. Which you may have now exceeded.

A smoke test might be in order to identify any unseen vacuum/air pressure leaks.

 

If you can get ahold of spare ISC (IAC), MAP and /or TPS, give a try swapping them in.

And, if you can, borrow another Power FC.

(I think the stock ECU will run a range if the TPS is failing. I don't know if Power FC does as well. )

 

Here is my Power Fc caught in the act of self adjustment. Try and find this screen on your commander.

When we got the UIM off we found my eight year old industrial vacuum lines (FPR/Oil Injector assist) had gone to dust in their casings.

 

Does the car have a working sequential setup or is it single turbo? Verify the throttle body is all the way closed when the throttle is not applied, and then start looking for a vacuum leak.

 

Check all vacuum lines, I was having this issue and the shop replaced all the vacuum lines and it fixed the issue. To include replacing the o-ring around the oil cap.

 

Hi @cewrx7r1 I do have a power fc.

how would i diagnosis with that?

I have been tuning with the FC Tweak. The car has been great. Then all of sudden this idle issue started out of nowehere. The car still drives insanely clean and strong except for this idle issue.

The issue came up after a 30 minute drive. It wasnt like i dropped a new tune in and it started having this issue. Its also not like i was messing with hardware either. So its just random. The air is cooler here in CT (although i do have meth). So there is that too

One thing i am keeping top of mind is that i keep reading that the power fc is pretty temperamental. even if nothing changed, since i been changing maps, idle settings, and so on. What could have been "ok" before in terms of air getting thru plates is not "ok" now. I do think there is a too much air situation and i think the power fc is doing this hunt on its own.

so far i have done the following:

-Adjusted TPS slightly
- Reset the power fc to the idle tune process

My plans are below and i will likely test the idle between each step.

- Clean the IAC. even though the idle doesnt correct when pull the wire connector out. I still think if its stuck it could be letting in too much air
- Check the butterfly valves are closing. Maybe there is carbon impacting them
- adjust air idle screw to full tight then back off 1/4 to 1/2
- Do another reset of the power fc
- Then do a vacuum leak test with a smoke machine

 

i am coming around to the notion of a vac leak. I bought a smoke machine.

My vacuum is dropping considerably during the oscilation.is that a symptom of a leak or a symptom of the oscillation?

Another thought i seem to be getting is that the motor went. I find this to be way outside the realm of the truth. The car absolutely screams to redline. and is super smooth. Its just the idle.

 

Thanks @Redbul

By the sounds of your video. do i hear the idle smoothing out at the end though?
i want to make sure i understand your analogy. sorry. Are you saying you had a vacuum leak on some of the smaller diameter hoses in the rats nest?

 

Thanks @Molotovman I do agree about checking if the throttle butterflys closing.

I want to do that. I assume i need to take off the intake elbow. I havent done this before. I think there are four bolts on each corner and a rubber o ring type gasket in between the elbow and throttle body. Is there anything else i need to look for or do to remove it?' should i replace the rubber gasket?

The car has bnr twins setup parallel.

 

duplicate post by mistake,

but ty for all the love today in the form of responses.

 

Giant o-ring between big intake elbow and TB may show to be brittle or damaged. Perhaps get one from your Mazda dealer (or elsewhere).

When you have the elbow off, check the coolant lines lines to the TB (if they are still there). They are often a source of coolant leak on old cars.

 

Yes that is the idle smoothing out after I briefly blip the throttle.

That wowwing was shorter and less frequent. Only when it seemed the ECU was not able to remedy the wowwing, did we investigate. Lately the wowwing is creeping back, so I suspect a new vacuum leak is developing.

I have a super simplified vacuum system with both twins parralleling and emissions delete; so the number of solenoids and vacuum lines is significantly reduced.

The two vacuum lines that were notably rotten were the two lines to the oil injectors (I premix in anticipate that sort of problem) and the vacuum line to the FPR (I have eliminated the FPR control solenoid, so vacuum is direct from the manifold.) If the FPR is not getting vacuum, the FPR will close and force higher fuel pressure into the injectors.

We replaced all the vacuum lines we could reach easily with the UIM off. But there are still vacuum lines to the turbo, and other, actuators that probably need attention.

 

BTW. There is a little idle air adjustment screw on the face of the TB (lower right side). Is it still there?

Also check the larger vacuum assist line to the brake pedal booster can. That line should have a check valve hidden in it.

 

Thanks. i am going to push some smoke through the system starting at the intake elbow for now. Still unclear if that smoke will make it through all the necessary lines given all the valves and etc. I started a new post on that subject.

 

The pro smoke generators hook up to four or more points on the system.

You may see some leakage around the throttle body axles, which is common.

 

Matty,

Email me at cewrx7r1@yahoo.com and maybe we can talk tonight.

Chuck