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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.
weve done that already, well before we did the smoke test. nothing.
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?
that adjustment screw behind the intake box on the left strut tower, that's not the variable resistor?
Remember, the motor is an S5 but the car, ecu wiring harness, and maybe even the ecu (because it was swapped into the previous car as well) are s4. the car, and ecu wiring harness being s4 NA while the ecu is a turbo II.
I have the unpopular opinion regarding the smoke test, in that I think compressed air is more effective. I seal off the turbo inlet, disconnect the map sensor line, and use that port to pressurize the system. 20psi is plenty. You will hear any leaks start hissing. (engine not running for this test)
The other problem I think you have to figure out is what parts you are running or intend to. The difference between an S5 TII block and an S4 is fairly minimal. If the resistor is out of spec, or you have a gremlin, that could cause a problem with the idle mix for sure. In addition, any vacuum systems that are hooked up need to be inspected and made sure they are hooked up correctly. Different vacuum ports maintain different pressure differentials based on their sources. Adjacent ports on the throttle body don't necessarily maintain the proper source if you are picking and choosing. One example would be your fuel pressure regulator vacuum source.
Also, has the throttle body been monkeyed with? Might be worth making sure some goof hasn't gotten ahold of it too.
Stock ECU, 550cc primary injectors until you get it figured out
I have the unpopular opinion regarding the smoke test, in that I think compressed air is more effective. I seal off the turbo inlet, disconnect the map sensor line, and use that port to pressurize the system. 20psi is plenty. You will hear any leaks start hissing. (engine not running for this test)
The other problem I think you have to figure out is what parts you are running or intend to. The difference between an S5 TII block and an S4 is fairly minimal. If the resistor is out of spec, or you have a gremlin, that could cause a problem with the idle mix for sure. In addition, any vacuum systems that are hooked up need to be inspected and made sure they are hooked up correctly. Different vacuum ports maintain different pressure differentials based on their sources. Adjacent ports on the throttle body don't necessarily maintain the proper source if you are picking and choosing. One example would be your fuel pressure regulator vacuum source.
Also, has the throttle body been monkeyed with? Might be worth making sure some goof hasn't gotten a hold of it too.
Stock ECU, 550cc primary injectors until you get it figured out
thanks for the help. I have to remove the intake manifold and turbocharger because the lower intake manifold decided it didn't want to be in one piece anymore (basically a huge chunk of aluminum just broke off as i was putting the damn thing back together.... yay me....), so i'm getting that replaced. when i took it off, it looked like the gasket was fubar, and the previous owner didn't even bother removing the old gasket, i'm getting that replaced and we'll see what happens. i also replaced my broken resistor with the one that came off the parted out vehicle the engine came off, and that was never fiddled with because it looks as if it was blocked off from factory, so we'll see if that help any as well. ill keep you guys posted, and reply if any of it worked.
thanks for the help. I have to remove the intake manifold and turbocharger because the lower intake manifold decided it didn't want to be in one piece anymore (basically a huge chunk of aluminum just broke off as i was putting the damn thing back together.... yay me....), so i'm getting that replaced. when i took it off, it looked like the gasket was fubar, and the previous owner didn't even bother removing the old gasket, i'm getting that replaced and we'll see what happens. i also replaced my broken resistor with the one that came off the parted out vehicle the engine came off, and that was never fiddled with because it looks as if it was blocked off from factory, so we'll see if that help any as well. ill keep you guys posted, and reply if any of it worked.
I'll be the LIM wasnt seated correctly when you tightened it down and thats probably why it broke. Better double check the mating surfaces.
I'll be the LIM wasnt seated correctly when you tightened it down and thats probably why it broke. Better double check the mating surfaces.
While im doing that, im also replacing the old lower manifold gasket. Im curious, can i use the S4 gasket on the s5 lower manifold? this is the gasket that mates between the manifold and the engine block.
While im doing that, im also replacing the old lower manifold gasket. Im curious, can i use the S4 gasket on the s5 lower manifold? this is the gasket that mates between the manifold and the engine block.
All of the LIM to Engine gaskets are the same for FCs. I just found out today that if you put a S4 LIM on a S5 engine, you need to grind on the rear iron or housing a bit. Just a FYI in case thats your case, may be why your intake manifold broke.
All of the LIM to Engine gaskets are the same for FCs. I just found out today that if you put a S4 LIM on a S5 engine, you need to grind on the rear iron or housing a bit. Just a FYI in case thats your case, may be why your intake manifold broke.
no, where it broke was between the lower and upper intake manifold, on the far corner where the bolts attach. thats where it cracked and broke off, one huge chunk. I think it was just over-torqued one too many times....
Ok, so i Figured it out. Was one of these two things:
gasket on the lower intake manifold was broken so i replaced that
the variable resistor was jank, and i replaced that with the one that came with the motor, which still had the factory Mazda cap, so no one has messed with it.
either way, the car isn't surging anymore, but now it has a heavy misfire, which i think is an easy fix
Ok, so i Figured it out. Was one of these two things:
gasket on the lower intake manifold was broken so i replaced that
the variable resistor was jank, and i replaced that with the one that came with the motor, which still had the factory Mazda cap, so no one has messed with it.
either way, the car isn't surging anymore, but now it has a heavy misfire, which i think is an easy fix
Glad you fixed it, but if you would have done the carb cleaner trick right off the bat you would have found it.
Glad you fixed it, but if you would have done the carb cleaner trick right off the bat you would have found it.
Just to say again, we did do carb cleaner to start with and found nothing. actually, it wassnt even a vacume leak, or that sensor i replaced. we found out that the thermo wax was causing the surging idle (as it was completely f***ed), and removed the system all together because while the throttle body it was trying to lower the idle, but the thermo wax was just increasing the rpm. Basically it was playing tug of war with the other settings on the throttle body.
However we now have another problem, now it idles extremely high (like 3k rpm when driven a short distance). i'm going to lower the screws for the primary throttle and see what happens. could be a simple fix but ill keep in touch
You mentioned that you had someone tune it. Is he also out of ideas?
When this surge is happening do you find that it evens out if you run the blower and have your lights on?
I am having this issues when the lights and blower are on the idles is smooth. turn them off and it goes back to surging.
What do you know can cause this?
Make sure the Throttle sensor TPS is adjusted to 1 volt.. . There are you tube videos to watch.
Make sure the idle adjustment screw is not full in or full out.
Ohm out or simply change the water temp sensor underneath the alternator.
Ohm out Bypass air control valve
Im running a FT550
my tps is calibrated.
My idle screw is in adjusted and idles fine with loads turned on.If I turn my lights or the blower motor off it start surging.
10-21-19, 04:10 PM
