S13 blacktop idle issues and rough low Rpms - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Sidewayz_610 · 07-22-2014, 10:43 AM

I'm having some weird idle issues and my car runs really rough at low Rpms. Like pulling out of an intersection slowly but as soon as I get on the gas a decent amount it runs great

The details:
S13 blacktop in s14 chassis
Stock Ecu
No bov (closed system)
Walbro 255 fuel pump

Low idle for first seconds of running then either idle at 1500-1600 and sometimes Bouncing idle from 1500-2000 Rpms even when hot
Vacuum at idle is 22 at idle and then bounces between 20-22psi with the idle surges

Running very rich( I can smell a lot of gas but I know the fuel pump is causing some of that but it seems excessive )
checked all fittings for vac leak

Cleaned maf, throttle body , pulled and cleaned iacv

I don't know sr's very well but I've done alot of research and tried everything I could find and still no luck

jakemkz · 07-22-2014, 10:59 AM

1. Check codes on the ECU (Some E5 ECUs have a diagnostic light, others don't so you may need to do a small amount of wiring to get this working but it is worth it)

2. Run ECU in O2 Sensor diagnostic mode to verify O2 senor is functioning properly. The ECU generally responds to a faulty O2 sensor by enriching the charge.

For red tops the FSM specifies idle RPM as 900 with high idle at 1200 during cold start and AC operation, would assume this is the same for a blacktop. Check to make sure the throttle stop screw is set appropriately, follow the service manual.

cotbu · 07-22-2014, 12:22 PM

Quote:

Originally Posted by jakemkz

1. Check codes on the ECU (Some E5 ECUs have a diagnostic light, others don't so you may need to do a small amount of wiring to get this working but it is worth it)

2. Run ECU in O2 Sensor diagnostic mode to verify O2 senor is functioning properly. The ECU generally responds to a faulty O2 sensor by enriching the charge.

For red tops the FSM specifies idle RPM as 900 with high idle at 1200 during cold start and AC operation, would assume this is the same for a blacktop. Check to make sure the throttle stop screw is set appropriately, follow the service manual.

Good advice right there!

After you've pulled codes, and repaired if any!
Set idle and base timing. This is done in timing mode, with tps disconnected or with consult/consult program, tps connected. 850rpm
You could adjust idle with out being in timing mode, but it might not stay, and while in timing mode you verify base timing 15deg btdc. 2birds1stone
If that is set correctly the idle will be 850-900rpm and then your vacuum should be 18-20inhg. If it's not don't panic.

Your rich smell condition: smelling raw fuel will usually make you lean on a wide band. Do you have afr numbers? The fuel pump isn't making you rich!
Leaking injectors, bad or fouled spark plugs, boost vacuum leaks, poorly tuned, 02sensor etc. <--- long list can.

jakemkz · 07-22-2014, 03:00 PM

It just occurred to me that in addition to the idle calibration and other issues that Cotbu and I mentioned earlier your problem may be caused by a faulty thermostat. I believe the ECU uses the thermostat to determine if the engine is cold, and if it is cold both the fueling rate and idle rpm are increased. This is required under normal circumstances because when the engine is cold less of the injected fuel evaporates and mixes with air. If your engine thinks it is cold all the time it will run very rich and always idle at the "cold idle" rpm. Good luck with your fix, please let us know what repair works out for you.

07-22-2014, 10:43 AM	#1
Sidewayz_610 Join Date: Oct 2013 Location: Coopersburg pa Age: 31 Posts: 29 Trader Rating: (0) Feedback Score: 0 reviews	S13 blacktop idle issues and rough low Rpms I'm having some weird idle issues and my car runs really rough at low Rpms. Like pulling out of an intersection slowly but as soon as I get on the gas a decent amount it runs great The details: S13 blacktop in s14 chassis Stock Ecu No bov (closed system) Walbro 255 fuel pump Low idle for first seconds of running then either idle at 1500-1600 and sometimes Bouncing idle from 1500-2000 Rpms even when hot Vacuum at idle is 22 at idle and then bounces between 20-22psi with the idle surges Running very rich( I can smell a lot of gas but I know the fuel pump is causing some of that but it seems excessive ) checked all fittings for vac leak Cleaned maf, throttle body , pulled and cleaned iacv I don't know sr's very well but I've done alot of research and tried everything I could find and still no luck __________________ Instagram : @colin18moyer

07-22-2014, 10:59 AM	#2
jakemkz Join Date: May 2014 Location: MA Posts: 39 Trader Rating: (3) Feedback Score: 3 reviews	1. Check codes on the ECU (Some E5 ECUs have a diagnostic light, others don't so you may need to do a small amount of wiring to get this working but it is worth it) 2. Run ECU in O2 Sensor diagnostic mode to verify O2 senor is functioning properly. The ECU generally responds to a faulty O2 sensor by enriching the charge. For red tops the FSM specifies idle RPM as 900 with high idle at 1200 during cold start and AC operation, would assume this is the same for a blacktop. Check to make sure the throttle stop screw is set appropriately, follow the service manual.

07-22-2014, 03:00 PM	#4
jakemkz Join Date: May 2014 Location: MA Posts: 39 Trader Rating: (3) Feedback Score: 3 reviews	It just occurred to me that in addition to the idle calibration and other issues that Cotbu and I mentioned earlier your problem may be caused by a faulty thermostat. I believe the ECU uses the thermostat to determine if the engine is cold, and if it is cold both the fueling rate and idle rpm are increased. This is required under normal circumstances because when the engine is cold less of the injected fuel evaporates and mixes with air. If your engine thinks it is cold all the time it will run very rich and always idle at the "cold idle" rpm. Good luck with your fix, please let us know what repair works out for you.