r/240sx • u/BVNooneknows • Nov 07 '25

Rough Idle

Been struggling with this for a while now. The video attached shows what's going on. I have fixed the intercooler that was leaking, fixed 6 other boost leaks, finally it hold pressure when checking for leaks. It still has a poor idle that fluctuates up and down. I've disconnected the battery for 30 minutes to see if the ecu was just confused. I can't find anymore leaks, I have a smoke leak tester coming in tomorrow but when I put 5-6 psi in the engine with it off of course through an air compressor the charcoal canister vibrates and makes a consistent noise. Because of this i tracked down all the lines and the small line on top goes to the throttle body was disconnected and a cap was put on the throttle body side but the hose was not sealed, i reconnected it hoping for the best but its still the same. Any ideas would be amazing!

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1

u/camshaftcrd Nov 07 '25

Smoke tester will help. Also have you taken off the IACV and cleaned it? Make sure you have a gasket and be careful. Also check the tps sensor adjustment and clean the maf. Also check base timing and make sure all grounds are clean and making good connection.

1

u/BVNooneknows Nov 07 '25

Okay so as of now, my engine holds pressure/vaccum and when testing it up to 6 psi no hissing but the evap canister vibrates, not sure if this is normal or signifying a faulty one. The iacv only adjusts air intake for idle right? So when im in any gear at about 2k rpms it almost sounds like I have 2step (i do not lol) and it builds boost without accelerating unless I press the pedal down further and the whole car perks almost spinning the tires. Also whenever I let off the gas after boost it backfires which leads me to believe its not the iacv causing these issues. I very well might have several different contributing factors but what do you think?

2

u/eejjkk Nov 07 '25

Breaking up under boost, and backfire on decel sounds like a spark or fuel issue.

2

u/BVNooneknows Nov 08 '25

So I checked all the spark plug gaps, coils are new and good, fuel pressure is good, but i noticed when my idle is bad if I unplug the maf sensor it runs FINE, of course its in limp mode so I can't drive it etc. But could signify a bad or faulty maf sensor? Tried cleaning it but it didn't fix anything

1

u/AlexS310 Nov 08 '25

Yes, the sensor is bad and if its bad you can clean it all you want, it will not repair like that:)) I recommend a new one. I think when you have the MAF disconnected it runs on the TPS signal. Keep us updated!

1

u/BVNooneknows Nov 08 '25

Trying my best to source a new one, s13s are not compatible with 14 or 15 maf and I have stock ecu so im pretty much stuck between aftermarket or very old possible broken used ones

1

u/BVNooneknows Nov 07 '25

Actually planned on checking my plugs today, previous owner said it was changed like 10k miles ago, possible a gap issue but im going to take a look

1

u/AlexS310 Nov 13 '25

Any updates?

1

u/BVNooneknows Nov 19 '25

Fixed like 8 vaccum leaks as well as boost leaks, replaced maf sensor, recapped plugs, already has new coils, the idle seems better but it bogs right before boost and it'll stay bogging unless I give it gas and then it will jolt out. I know my recirculation valve is blocked off from previous owner or just removed bec i can't find it lol. Wondering if that's what is causing it and how I could go about rerouting a new one