Need Help. SR wont idle anymore...

[mobbin240]

so im stumped... i cant get a good idle out of my SR. it will stay idling if i feather the throttle on and off... wierd...
ive checked the ECU diagnostic mode.. code 55= ALL GOOD/NO FAULTS.....RIGHT?

im sure my CAS is set properly.. the motor fires and idles. but not for long. was better in the summer...

ive checked spark and fuel

ive checked for good power and ground on the O2 sensor. its new genuine nissan part. What are the measurements for this?

ive replaced the MAF sensor with a HITACHI brand 3 wire SOHC unit. has good power and ground. what is the measurement for this?

ive checked the IACV and it has vacuum at the intake tube, even sprayed it with carb cleaner for good measure.

ive checked the TPS and it is at 0.45v Closed throttle and 4.11v WOT... what is the parameters for this? i believe .45 is good for closed... but is 4.11 too high for WOT? OPINIONS?

finally if everything is truly "ALL GOOD"
Maybe bad Coolant Temp Sensor? Bad Fuel Pressure Regulator? Vacuum Leak?

i just need ideas guys. help me out.

[YoungS13]

I would swap out your coolant temp sensor and see what happens. I dont have an SR but on my KA my coolant temp sensor was bad and it was messing with the start up and the idle. Maybe it will help. Good luck!

[2_Liter_Turbo]

Things to check for bad idle performance (but run ok under throttle) on SR's and other NIssan engines from my experiences:

Bad Coolant Temp Sensor (Has usually been the culprit with my cars, buy OEM, I've had bad luck with aftermarket).
Cracked Vacuum lines (More common KAs vs SRs)
Intake manifold gaskets (All the ones touching the manifold)
Bad AICV (Easy way to check is to unplug it or clamp off the air hose going to it to see if you get any changes)
TPS
Intake/Intercooler Coupler's (cracked or loose clamps)

I'm sure there can be more, but these have been culprits with my cars over the years. Good luck!

[centralcoaster33]

2nd the above, temp sens, the one to the ECU, OEM is best, with MAF added to list.

[mobbin240]

Ok. all the hose clamps are tight.
the MAF is brand new hitachi unit
the TPS has .45v closed and 4.11v open is this ok measurements? or is WOT too high?

The thing about the IACV. it confuses me. i have strong vacuum at the intake tube. but i connect cold pipe and it boggs. it wont rev under throttle. it also boggs. i have to go on and off throttle sequentially to keep idle.
if i hold the throttle dowN about 2 inches as i start it and let off after ignition it smooths out for a second then starts to die...
i was thinking vacuum leak, fuel pressure regulator, Coolant temp sensor, or IACV as the very last thing. MAYBE TPS.. but i dont know the measurements for this...

[2_Liter_Turbo]

The TPS sounds about in the ball park. Check out the S14 SR20 FSM via the link in my signature. It has all the testing info. The AICV should be getting air from the cold pipe, not the intake tube. You can try pinching the fuel return line and see if that improves. That is a quick way to see if the FPR is faulty.

[mobbin240]

Thats what i mean. The little tube that come off the cold pipe by the TB

[2_Liter_Turbo]

Ahh, my bad