Hi All

01 JDMbugeye completely stock.

Recently out of no where I had the infamous high idle and error code for idle system malfunction po507 or whatever other is. Car was driving perfect previous time I drove it.

Basically idles at 1k rpm in close loop at 14.7afr. Drops to 750ish with ac on.

As soon as u blip throttle its like the throttle is stuck and the revs hang. When it goes open loop and you hold a steady throttle its seriously lean like 23afr. This throws the idle fault code.

I did a bit of a on load run and open loop and on boost its was lean 12.5afr compared the low 11s like it normally is. It also detected knock even in IAM of 8 so I assume the lean condition was an issue. I didn't push it after this as clearly something wrong. I dint think it's unmetered air either as the maf g/s was almost identical to a log I did a few weeks prior for same boost level load rpm etc.

Def not throttle cable. Cleaned throttle body which wasn't dirty anyway. Checked butterfly shuts properly.

Its like its a post Throttle body vac leak the way it hangs.

replaced the IACV as my old one was almost instantly throwing the code cleaning it didn't work. This helped alot it would actually idle relatively smooth but still high at 1000rpm

I've checked for vac leaks and found a couple tiny ones like the BOV gasket amd surprisingly the new iacv was leaking around the motor casing. I bought another 1 from somewhere else.

Smoke tested inlet manifold with the airbox bung in. Nothing. Sprayed carb cleaner and water around all intake manifold gaskets/ where tgv go (jdms don't have the actual valves just the body things there.) and around injectors.

the turbo intake pipe is def good as i bunged the intake pipe and turbo outlet and it more or less held pressure and also vaccum. It does eventually leal away but very slowly. No bubbles ever formed with soapy leak detector spray. The smoke tester didnt leak any smoke either for the same arrangement. If I backed off the turbo inlet pipe hose clamp it would leak smoke from there so I know my setup must work properly.

Checked wiring and voltage to iacv all OK .

Put on my old known working MAF and my maf is pretty new. Cleaned with contact cleaner.

The o2 sensor is new as it was throwing an o2 code down the back straight at bedford at like 100mph. I couldn't replicate this again up to 90mph on the road. The old one which was only 2 years old was all rusty looking from i think using to much octane booster mmt or whatevers in them from various tracks days in the last few yeads. This was data logged and everything was OK no knock not lean a few weeks prior when I changed it.

Coils are fairly new. New spark plugs they were also MMT fouled from the octane boost i though this mightve been it. Same plugs as last time ik22 denso heat range OK for the jdm and 0.8mm gap I chucked a bore scope into cyl 3 which I believe is known to run lean compared it to another cyl they looked fairly similar. 3 was maybe a tiny bit cleaner.

Fuel pressure tested correct and changed accordingly with the fpr disconnected ie it incread approx 9psi with fpr vac line removed.

Injectors all sound like theyre ticking the same.

Checked fuel pump strainer all ok. Fuel pump Walbro isnt that old either.

Replaced fuel filter

I haven't leak down tested the motor yet but it was running perfectly one day then I went to drive it a few weeks later and yeh High idle. Doubt it just randomly dropped a valve or something

I mucked about with the tps a bit but it always read 0 and 100% respectively. Measured voltage at ecu and ot was 0.55v. It didn't help

Pinched off rhe brake booster line thinking it might be leaky brake booster

New pcv this week and all the hoses i replaced like 2 years ago. Again no smoke from smoke testing.

Neutral switch is confirmed working from the pins on the ecu. Changes state every time when in out if gear

My gut is telling the injectors are clogged as in open loop it runs **** but close loop idle almost is ok.

Weird thing is it got stacks of timing in the log but the injectors duty cycle is 0% with only slight throttle position as seen in the log photo iv3 posted holding a steady throttle in neutral.

The lv fuel trims also seemed to be pulling fuel in the lowest cell -5%. Clearly its lean though.

When warm the maf g/s is approx 5 same with my older known working maf.

Any help appreciated as ive seriously think I've triple checked everything you usually look for before cleaning the injectors or pulling the inlet manifold. As per any forums search.

Below screen shot of log is 8% throttle in neutral. Sounds like the plugs are fouling but they're new. Possibly coils even though they aren't that old ?