Idling Rich

[NotoriousGT350]

Story: On loop here and was exiting. As I was approaching the red light and pressed the clutch to get out of gear, all of sudden idle drops to 400-500rpms, idles back up to 1100rpm before settling down. Exhaust sounded like it had a stutter here and there, drove home and parked it. Got my old diablo programmer I use for codes and nothing popped up. Let sit over night, did a cold start up today and it was smoking a little whitish, smelt rich as my eyes were burning, looked at the Wideband reading 12.5-13 AFR. Shut off, replace my NGK TR6s with new ones, gapped 0.028, and placed a new FRPS. Also cleaned the MAF sensor. Started her up and same thing. AFR 12.5-13, sputters a little , some white smoke on start up and goes away.

Mods in sig I believe.

Thoughts??? New coil packs needed? Car has around 44K miles.

 

[MG0h3]

Do you have cats? Any car with no cats will burn the eyes a little.

Those AFRs are normal during warm up.

It’s cold and wet now; seeing some white (condensation) out the tails is normal. Not sure where you’re located.

The most common stall or low idle when coming to a stop is tube related. But I’m guessing you’ve had the car for some time and this is a new problem?

Did you recently have a dead battery or anything?


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[NotoriousGT350]

No cats, Off road Pro chamber. I did let it warm up again and seeing AFR 12.5-13. Temp outside in mid 60s, it's not condensation. Had the car since '05, blown a few FRPS before, Optima battery is good showing 14.1 volts.

I have been contemplating getting a new tune anyways, upgrading the fuel lines to PTFE hoses from tank to rails so I don't have to worry about garage smelling like gas from the stainless steel braided lines that are old. My tune is about 11 years old and has done great over the years, but tuner is no longer around.

 

[MG0h3]

Strange that you don’t have a code for running rich.

I mean let’s assume that the WB and your nose are correct, O2s should be trying to drive that down.



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[NotoriousGT350]

May look over again this weekend. Maybe bad sensor.

 

[MG0h3]

Not sure if you can log but that would be a good way to see what’s going on


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[01yellercobra]

Log the short term trims. Make sure the wideband isn't lying. Tunes don't randomly go bad.

 

[NotoriousGT350]

Okay, got some pics as and videos.

 

[NotoriousGT350]

O2S12 reading lower?

 

[JaCobro]

Check if oil smells like fuel? Could point to a leaking injector if it does.

 

[NotoriousGT350]

It did a little yesterday, that’s why I changed out the FRPS thinking maybe it went bad.

 

[BlckBox04]

I’m having the sane issue too. But my car is throwing o2 and over fueling codes and I have a return system.

 

[hotcobra03]

Open/closed loop
Do these numbers change?


I use this tuner on mine
Chasing 171/174
Mine were +25

was lower intake hose leaking at nipple.

 

[NotoriousGT350]

Going to check the air filter in fender well and any vacuum lines. I’ll turn on the monitor for open/close loop and see what happens. Anything else?

 

[hotcobra03]

Chilton Library

Scroll down to enter resource link.

PC/ED section of our manual.

all the codes and fords pinpoint tests to follow for repair.

Pinpoint test H. Fuel control
Is what your looking for.

also has section on basic systems parts how they work

like fuel trim

This works on cell.

For laptop we have the full manual on this site. Svt documents
Scroll down. Service manual.
Icon on left at start of paragraph is the click button for that download
Home
hard copy listed is just workshop and minor color wiring

 

[NotoriousGT350]

Great reading material to look at. Cleaned the filter and connections were good, no vacuum lines I could find that were disconnected. Battery died which was odd after all this happening.

Charged up my Optima battery, went to Parts store to check the charging system and all checked well. Upon driving and cruising around 2000-2200 rpms, AFR is spot on. As soon as I barely get off the throttle, drops to 11:1 to 12:1. Got home and on my tuner I noticed “FPM” on and off constantly. That’s just sitting in the driveway idling and both my LTFT were -25% and both STFT were 25%.

Anything else I can monitor to help guide me.

 

[03cobra#2]

Great reading material to look at. Cleaned the filter and connections were good, no vacuum lines I could find that were disconnected. Battery died which was odd after all this happening.

Charged up my Optima battery, went to Parts store to check the charging system and all checked well. Upon driving and cruising around 2000-2200 rpms, AFR is spot on. As soon as I barely get off the throttle, drops to 11:1 to 12:1. Got home and on my tuner I noticed “FPM” on and off constantly. That’s just sitting in the driveway idling and both my LTFT were -25% and both STFT were 25%.

Anything else I can monitor to help guide me.

What are you using to datalog?

 

[NotoriousGT350]

Old diablosport tuner I kept for codes, etc

 

[hotcobra03]

something I did during search on vacuum hoses

I pulled the vacuum harness from car and bench tested lines

I blew into line and sucked back

I did find one with restriction and one with a burn spot on egr green line

here is another link with color pics of vacuum hoses

https://www.svtperformance.com/threads/03-04-cobra-vacuum-lines-documented.733504/

 

[hotcobra03]

Fuel System Monitor
The Fuel System Monitor is an on-board strategy designed to monitor the fuel trim system. The fuel control system uses fuel trim tables stored in the PCM's keep alive memory (KAM) to compensate for variability in fuel system components due to normal wear and aging. Fuel trim tables are based on engine rpm and engine load. During closed-loop fuel control, the fuel trim strategy learns the corrections needed to correct a "biased" rich or lean fuel system. The correction is stored in the fuel trim tables. The fuel trim has two means of adapting; Long Term Fuel Trim and a Short Term Fuel Trim. Both are described in greater detail in this section under Powertrain Control Software, Fuel Trim. Long Term relies on the fuel trim tables and Short Term refers to the desired air/fuel ratio parameter "LAMBSE". LAMBSE is calculated by the PCM from HO2S inputs and helps maintain a 14.7:1 air/fuel ratio during closed-loop operation. Short Term Fuel Trim and Long Term Fuel Trim work together. If the HO2S indicates the engine is running rich, the PCM will correct the rich condition by moving Short Term Fuel Trim in the negative range (less fuel to correct for a rich combustion). If after a certain amount of time the Short Term Fuel Trim is still compensating for a rich condition, the PCM "learns" this and moves the Long Term Fuel Trim into the negative range to compensate and allows Short Term Fuel Trim to return to a value near 0%. Input from the ECT or CHT, IAT, and MAF sensors is required to activate the fuel trim system, which in turn activates the Fuel System Monitor. Once activated, the Fuel System Monitor looks for the fuel trim tables to reach the adaptive clip (adaptive limit) and LAMBSE to exceed a calibrated limit. The Fuel System Monitor will store the appropriate DTC when a fault is detected as described below.

1. The heated oxygen sensor (HO2S) detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio.
   

1. A correction factor is added to the fuel injector pulsewidth calculation and/or mass air flow calculation, according to the Long and Short Term Fuel Trims as needed to compensate for variations in the fuel system.
   

1. When deviation in the parameter LAMBSE increases, air/fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the fuel trim table has clipped, the Fuel System Monitor sets a Diagnostic Trouble Code (DTC) as follows: The DTCs associated with the monitor detecting a lean shift in fuel system operation are DTCs P0171 and P0174. The DTCs associated with the monitor detecting a rich shift in fuel system operation are DTCs P0172 and P0175.
   

1. The MIL is activated after a fault is detected on two consecutive drive cycles.
   

Typical Fuel System Monitor Entry Conditions:

• RPM range between Idle and 4,000 rpm.
  
  
• Air Mass Rang greater than 0.75 lb/min.
  
  
• Purge duty cycle of 0%.
  

Typical Fuel Monitor Malfunction Thresholds:

• Lean Malfunction: LTFT > 25%, STFT > 5%.
  
  
• Rich Malfunction: LTFT < 25%, STFT < 10%