Paulc19

installed this new turbo a little while ago, has a bad surging problem (idle bounces from 900/1000 to ~1500 and back, doesn't stop at any temp). I've looked everywhere and couldn't find info that could point me in the right direction.
we've replaced the tps sensor and adjusted it to spec, and noting. i replaced the BAC valve, no dice. no vac leak either.....
the only thing i can think of now is that coolant hose running to the throttle body and the BAC valve because the previous owner blocked all of that up. But at the same time, when i saw it run in the car i bought it off of, it idled perfectly fine.... whats the deal?
I have an rtek ecu and someone to tune it for me, could using the aftermarket ecu instead of the stock one fix the problem? what about the coolant line i mentioned? any advice is greatly appreciated, I've been stuck on this for about 2 weeks now and I'm running out of patience -_-
we've also played with every single setting that affected the idle and none of them 100% fixed the problem.....

jl1rx7

iTrader: (1)

Go back to the basics. Check all vacuum lines, make sure they are crossed etc. check all electrical connections are good.
When you say previous owner blocked up the BAC, what do you mean by that?

professionalpyroman

What he said x10.

Check for vacuum leaks and try to get the system as close to stock operation as possible.

Rotary Alkymist

You mentioned that you had someone tune it. Is he also out of ideas?

Are you still running a stock PCV valve? If so pull the LARGE vac off during idle and confirm there is no vacuum below 2000(IIRC). There should be no vac at idle. If you do then you essentially have a vac leak.

When this surge is happening do you find that it evens out if you run the blower and have your lights on?

Paulc19

There was a BAC valve on the motor, the coolant running from the motor to the throttle body and BAC valve has been removed and the ports on the motor have been welded shut (i think that has something to do with the quick warm-up sequence). we found that the bac valve was off spec and replaced it but still no good.
all vacuum lines are secure, no vacuum leaks, we smoke tested the thing around 100 times already. tps sensor is also working as well, ive got a friend who has experience with rotaries and has owned a few who is also a ASE certified tech.
on the stock stock ecu we can tune the throttle body and variable resistor to where it would idle properly but give it a rev and it dies immediately because its too low. start it back up and its back to its bs again.
im getting new injectors because it turns out the rtek ecu wont work with 550cc injectors, so im upgrading them to 750cc to see if it feels better with the rtek than the stock ecu.

Paulc19

no vacuum leak whatsoever, even smoke tested it to be 100% sure, nothing, its completly sealed.

Paulc19

thats what my friend did to start. we could get it to idle but only at about 1k rpm (when the rpm drops when you let off the gas it drops well below normal idle where it tries to catch itself but ends up dying). once we revved the engine it immediately died. started it back up, and its back to doing it again.

Paulc19

I might as well post this as well. Since i'm going to be swapping over to the rtek7 ecu, i was told i would need 720cc injectors or higher. I got 750cc injectors for both primaries and secondaries but dont know if i also need a better fuel pump to compensate since i don't want to go past 300hp (in fact if i make 250 ill be pleased)

Rotary Alkymist

The smoke test wouldn't reveal this leak. This is an internal leak. If you didn't test your valve don't assume it's working correctly. It's a vacuum leak that will go unnoticed.
Also there is a check valve on one of the lines going into the inlet duct. This one way check valve will also pass the smoke test leaving you wondering wtf is going on.

Those two valves take a minute to check. I would cross them off your list of possible culprits.

Paulc19

if your talking about the bypass air control valve, we checked it before we did the smoke test, its working properly and to Mazda spec.
edit: ok, i went back, if your referring to the PCV valve i don't even think its there, is that whats causing this?

jl1rx7

iTrader: (1)

He is talking about two green/white check valves in the vacuum system. He might to be on something, like the are backwards or clogged. Possible in the wrong locations. If I recall correctly the FSM has a routing diagram for them.

In regards to the plugged water ports from the BAC and throttle body might be an issue. Again if memory serves, use water to heat up a wax pellet and switch ports for what is in warm up mode or not.

Another check to do is get a hand vacuum pump, pull a hose, pull a vacuum and see if it holds. Pneumatic systems are no different that electrical system diagnostics. Make sure you have air in the right spots.

Also the ECU you are running with 550 CC injectors, is it currently stock? I would get stock to work before switching over to anything. You could be chasing your tail for no reason.

Paulc19

good point, ill leave the stock ecu where it is for now and see. and yes for the most part aside from the emissions being deleted and me having to modify the NA ecu harness for the knock sensor, yes it is stock.
Edit: also something i think people should know, the car in the configuration it is in right now is nearly the same as when it was in the previous vehicle and i watch with my own eyes how that thing preformed and it wassn't pulling any of this.

Rotary Alkymist

Page F2-7 in the FSM -Do you see that valve labeled Check Valve(One Way)? Check to see if you actually have it and if you do test it. If it's not there this could be causing an issue. Solution(for testing purposes only) unplug that line and plug both ends with your fingers and see if the problem goes away.

On the same page do you see the valve labeled Purge Control Valve? Test it by unplugging the large vac line on the "middle iron" and feel for vacuum. If you feel vacuum at idle then the valve is faulty. Even more apparent is when you have your thumb on the line your car with idle properly.

Paulc19

that check valve has been removed. The previous owner removed it for a front mounted setup compared to the top mount i'm using. He had an hks sequential bov. as for the POV, i just checked, and no i don't have one of those either since it looks like that's linked with all the emissions stuff, which has all been removed.
EDIT: this engine was running in the previous vehicle it was in with all of these items removed, the only differences being that i converted it back from a front mounted intercooler to a top mounted intercooler, and i also replaced the injectors because the ones on the motor looked pretty fubar. I dont know what size injectors were being run previously but im running the 550cc stock injectors at the moment.

Rotary Alkymist

Does the behaviour change when you turn on all accessories?

I would start suspecting a timing issue. Drive the car for 30-45 minutes and give 'er from time to time. Then drive home and put your timing light on it. If you don't have a timing light it's time to buy one lol. Be sure to SHUT ALL ACCESSORIES OFF AND JUMP 2 PIN GREEN CONNECTOR by the battery.
Only then can you check with your light(have your tap on L1). You might be surprised to be a couple of degrees off. You'll also find that minute rotation of the CAS has a dramatic affect on the timing.

This is what I've found -when timing is out by a bit the ECU is always compensating and is also in a state of constant confusion. Accessories also compound this issue because the ECU is designed to compensate for the accessories as well and the ECU will only compensate correctly if the crank is actually timed correctly. With the timing being out the ECU will know it's out and will try to fix it forever by adjusting timing and fuel.

You could be 5 degrees off and it'll start and seem to run fine to most but the idle will give it away. If you had duty cycle on your injectors you would see that something is causing the ECU to fluctuate through rich and lean mixtures.

Paulc19

its not a timing issue. the primaries are perfect and spot on to spec, the secondaries seem to have a very minor misfire from time to time, but its only about once every 3 seconds or so. basically the secondaries are in sinc and for 1 rotation every 3 seconds or so the timing would drop a hair, but that's it, it would go back up and resume idling like normal after that. If it were a timing issue, im almost certain we wouldn't have gotten it to idle once in our time fiddling with the settings on the throttle body.
and there's not difference if the accessories are on or not.

Rotary Alkymist

Have you put a timing light on to confirm?

Paulc19

yes, twice even.

Rotary Alkymist

Have you tested the O2 sensor?

Paulc19

yes, i even pulled the o2 sensor from my spares which i know works and i got nowhere.

Rotary Alkymist

'Getting low on ideas.

Does anything change when you ground the test connector?

Engine info would be helpful. JDM?

Paulc19

heres the history of the motor that i can sum up: original owner bought the fc turbo in the usa, he modified it (deleted the emissions, and gave it a front mounted intercooler with an hks BOV, but ran into trouble with the wiring cutting out on him. he also swapped it at one point because it was an s5 motor in an s4 rx7 which threw me off for a sec. Long story short, the guy was low on cash, he sold it so his buddy, who parted the whole drive train out to me because he didnt know jack about rotaries. I installed it, ran it, and started tuning the throttle body to spec and that's when i ran into this problem.
Something i just figured out, however, is that my friend just tested my variable resistor and found that it was bad. Moreover, the person i bought the motor from never gave me his. Now i would put it into consideration but when i was running the N/A motor on my car before i swapped it over it ran with no problems whatsoever with the bad variable resistor.
one more thing: When i engage the clutch, it still bounces up and down but its also accompanied by a lot of popping from the exhaust (im assuming a misfire). when i let go of the clutch, the popping stops but the surging is still there.

Rotary Alkymist

If you are running s5 then there is no variable resistor.

still hard to say what you're running. What engine do you have in your car?

Rotary Alkymist

Have you tested your neutral switch?

FührerTüner

iTrader: (5)

I know you said you did a smoke test, but just to be sure spray some carb cleaner around all of the UIM/LIM while its idling and see if the idle changes. If it does you have a vacuum leak.

I had the same symptoms on my first FC. Ended up being the LIM/Engine gasket.