Mystery flooding/rough idle issues RB20DET

[TBird713]

So, as title says, having some major issues. The car now barely starts, pops a lot during idle, and gradually will get worse as I drive it. In the afternoon it wasn't doing too bad, but later on it started flooding out during a cruise if I held the throttle in the same spot for too long. When I went home it was to the point it wouldnt even idle. As soon as i would try letting the clutch and and give it slight gas to make it into my driveway it would just die. We've properly cleaned the injectors with a pressurized can, no luck. We've swapped mafs for a known working one, no luck. van is between -15 to -20 in.Hg and makes a healthy 10lbs of boost which it loves with no problems but maybe the neutral switch thinking its not in gear so it cuts power. ive figured that out so thats not a problem. But we've tried everything. We've sprayed every hose with brake clean and we get no difference. Has new yellowjacket coils and will be putting in brand new iridiums which i doubt will make a difference to my issue. We've sprayed all the intercooler piping. And on top of this without unplugging various tps and iacv plugs, it idles at 1700 and wont go down even after warming up. We're stumped. Help plz

[DatsunZ31]

coolant temp sensor? cam angle sensor?

[TBird713]

Coolant temp sensor is brand new and cam angle sensor is working properly as no codes and timing is set properly. Unless it can still mess things up with perfect timing and no codes i dont see it being a problem

[Skym]

Faulty MAF can make engine idle at around 1500rpm, but there's a MAF error code on ECU.

But ICAV when faulty can make engine idle at higher rpm. Or AACV is adjusted higher than normal.

Running rich can be due to lazy o2 sensor, as makes ECU make engine stay rich for longer (popping sound from exhaust). Unplugging o2 sensor should make ECU go into open loop (ignores o2 sensor input). o2 sensor should be checked and changed if necessary every 40-60,000km.

[TBird713]

Ya thing is i changed it for a new stock one straight from nissan and i know that maf works cuz it made no difference. iacv i also cleaned out. was pretty foulded up but nothing some carb cleaner couldnt take care of. tried unplugging o2. and iacv. can try again but pretty sure it made no difference. i know a lot of cars around here have the iacv unhooked cuz it buggers things up so often

[TBird713]

Well to be scpecific according to nissan fast i cleaned the AACV that is gasketed to the intake plenum. Ive tried blocking off the air regular but to no avail. Made zero difference at all.

[Skym]

Higher idle usually requires more air, hence why I'm looking at idle valves or anything airleak related.

If IACV is stuck open it can cause a high idle, sometimes it can get clogged by oil deposits (from blowby via PCV system or front turbo oil seal has failed in the past) which makes valve inside hard to close and needs to be cleaned or it just fails and needs to be replaced. Could be that AACV is set too high (idle needs to be reset), sometimes due to engine stalling and need a way to stop engine from stalling.

If was a intake manifold airleak, rpm would bounce up and down (rough idle) due to o2 sensor if intake manifold to head flange was leaking. Best way to tell is put a wideband in exhaust and see if engine is running lean or rich.

Old injector loom, coilpack loom are known to cause missing, same with leaking injector (if engine is running rich) which is another common problem when the engine ages.

[TBird713]

Well tested the injectors and they're ALL giving me 9.5 ohms (which seems kinda low). Air regulator is deleted and everything else cleaned. Still gotta put it all together again and do another test run but before i took things apart i was revving it on idle and it was hesitating. Like "bruuum--buuUUmm" and it wasnt me two stepping it either. just moved the throttle from position a to position b and held it and it two-steps. Ideas?

[DatsunZ31]

I'm just as new to RB20's as you are but I have been doing a lot of reading to catch up (i know the VG30ET platform like the back of my hand, mechanically RB and VG aren't too different) . could it possibly be a fouling ignitor? maybe a coilpack on the way out?

What color are the spark plugs? are you getting a nice whiteish spark?

[TBird713]

Ya know I havent checked but I will tomorrow when i resolder some wires and possibly install my SAFC I. Buddys mustang had a coil go bad. Still had spark but it was orange and coil was the issue. Ill give er a shot. Plugs are new and coilpacks are pretty well new, only 10k on em.

[TBird713]

SO. Fixed the maf wiring. Idles better BUT still hunts a bit and tries dying out. However reading back through previous threads I actually READ a comment by Skym.

"The 0.44V is where the idle contact pin is supposed to be. But idle contact pin can bend over time. Idle contact pin tells ECU to switch to idle, etc tables. If ECU doesn't switch to idle, etc tables, engine can start to stall (rev needle drops below idle rpm) when engine is put under load and could stall."

Dat pin. Thats exactly what it was doing when it died in my street. Would barely idle and as soon as the clutch started engaging and load was put on it quit. At like 1 in the morning. With 3.5" straight pipe. Everybody knew.

BUT that is what it was doing and its NEVER wants to idle down below like 900+. It should be idling at 650 in theory. I also did an ohm test on my tps between signal and ground pin and at closed (reading at 20k) i BELIEVE i got 0.19 and wot was 0.26. according to manual it should be 2.0 AND 10.0 (hurr durr) so i think my tps is pretty well pooched. Car also ran half decent with the 2 wire tps connector unplugged (what is it for?). Installing my SAFC tomorrow and putting in a wideband to see whats up. Thoughts?

[Skym]

There's the 0-5V curved track on circuit board inside TPS (popped the rivets and pulled TPS apart, thinking it could be fixed, but no). On one end of 0-5V curved track on circuit board is the idle contact and the other end is the WOT (Wide Open Throttle or basically foot to floor) contact. If I remember correctly, one of the plugs is the 0-5V for circuit board and the other plug is the idle contact, WOT contact plug.

I was looking into if could fit a optical TPS sensor (Toyota or similar) that doesn't wear out as easily. But only option I could find is fly by wire with Motec M600 ECU.

[TBird713]

Think it could be my problem though? I know my ohms DID change but the readings were way out to lunch and BARELY changed and it doesnt like to idle even after everything is cleaned and adjusted. I removed the air regulator and the diaphram was partially opened which i found odd since it was cool out and unplugged. Just taking the spring off stretched it so its obviously weak but should it be like totally open or closed when cold and unplugged? not like a quarter way? It out right now and hoses are plugged off so im not sure if its going to affect me much. Main issue was when idle was held at xxxxrpm for more than 2 seconds it would start bucking (and still does, took it for a rip yesterday after fixing maf wires) and sputtering and dying. Gets worse as the day goes on to point of barely running/dying.

[Skym]

Can check IACV on a hot plate, as it takes heat from engine (or hot plate), voltage from a battery to make valve close inside IACV.

[TBird713]

Well with it deleted and the SAFC in (which works wonderful) it was actually idling fairly smooth at about 950 today when it warmed up. cold start was a bit rough because its missing the extra air but im scared that if i put it back in it will bring the idle up again and then farting around with it will screw things up again. Might try just for the heck of it but im pretty scared too if its running fairly nice already haha