HEGO ?

Vehicle specific forum for tuning the Foxbody Chassis Mustangs utilizing decipha's GUFX Strategy

HEGO ?

Unread postby lugbolt » Tue Dec 17, 2019 7:23 am

I was playing with idle fuel yesterday and noticed that my HEGO's are not even. For instance, HEGO2 was bouncing around 0.2 volt and HEGO1 was bouncing around the rich side, 0.8v. My first thought was vacuum leak and the only leaks I could smoke out were at the throttle shaft of the 90mm accufab throttle body. Beyond that, nothing. It's a brand new throttle body but it's several years old, sat around forever before I put it to use. The old style F90's do not have sealed throttle shafts, or that's what accufab told me (and it doesn't set well with me either). Is that gonna be enough to cause a problem?
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lugbolt
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Posts: 34
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Vehicle Information: 1992 Mustang GT 408w, T56, Pro-M 92, 42lb, FTI 240/250 @.050/.610 lift hydraulic roller, 10.7:1, AFR205, street car.

Re: HEGO ?

Unread postby blocmi » Wed Dec 18, 2019 4:30 pm

Did you disable one HEGO or reassign injectors in your tune?

The reason I ask is because the commanded LAMBSE is identical for both banks, like both banks have been assigned to use the same HEGO.

If you did, it looks backwards to me, which could be an issue, but it would explain LAMBSE1 mirroring LAMBSE2, and why HEGO 1 isn't switching.

What is NUMEGO set to?
What is FN1327 set to?
blocmi
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Vehicle Information: 1995 Ford Mustang GT, 180K mile 302, CBAZA, U4P2, Quarterhorse, TunerPro RT, AEM WB, Ported GT40 Heads & Intake, E303, BBK 70MM TB, Cold Air Intake, 24lb Injectors, 80mm MAF, Adjustable FPR, FMS Headers, OR X-Pipe, C4 w/reverse manual valvebody, 3800-4100 stall converter, 4:10,

Re: HEGO ?

Unread postby lugbolt » Wed Dec 18, 2019 8:34 pm

FN1327:
1234 are all in blue, and all #1. 5678 are all in red and all #2.

NUMEGO shows 2

Unless I have screwed with them unknowingly, they are A9L2 standard.
lugbolt
Premium Member
 
Posts: 34
Joined: Fri Apr 26, 2019 7:56 pm
Vehicle Information: 1992 Mustang GT 408w, T56, Pro-M 92, 42lb, FTI 240/250 @.050/.610 lift hydraulic roller, 10.7:1, AFR205, street car.

Re: HEGO ?

Unread postby blocmi » Thu Dec 19, 2019 11:09 am

Hmmm... LAMBSE1 should be trying to trim the fuel on BANK1 until HEGO1 switches above and below .4 volts... and its not...
I wonder if HEGO1 is bad and the ECU has already determined it is failed in that log...
I know there is a setting for how long the ECU tries to adjust the trim fuel before it fails a sensor, but I don't know how long it takes or what the failure mode default is.

Some things I would look at:
If you do a hot restart does LAMBSE1 read differently from LAMBSE2 at any point, and more specifically, do they read differently around the time when they initially start switching.
Visual inspection of passenger side HEGO wiring... No burnt wires, grounds are good, etc...
Swap O2 sensors from side to side and see if the problem moves with the sensor.
blocmi
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Posts: 61
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Location: New England
Name: Mike
Vehicle Information: 1995 Ford Mustang GT, 180K mile 302, CBAZA, U4P2, Quarterhorse, TunerPro RT, AEM WB, Ported GT40 Heads & Intake, E303, BBK 70MM TB, Cold Air Intake, 24lb Injectors, 80mm MAF, Adjustable FPR, FMS Headers, OR X-Pipe, C4 w/reverse manual valvebody, 3800-4100 stall converter, 4:10,

Re: HEGO ?

Unread postby lugbolt » Thu Dec 19, 2019 7:15 pm

HEGO's are brand new (like under 5 min run time) NTK's but that doesn't mean that one of them isn't defective. HEGO harness is original; will have a look. Come to think of it, it had lean codes when the original 5.0 ran/drove so there may be an issue there. Code 41 and 91 as I recall. I never dealt with it knowing that the 5.0 was tired and fixing to come out anyway.
lugbolt
Premium Member
 
Posts: 34
Joined: Fri Apr 26, 2019 7:56 pm
Vehicle Information: 1992 Mustang GT 408w, T56, Pro-M 92, 42lb, FTI 240/250 @.050/.610 lift hydraulic roller, 10.7:1, AFR205, street car.

Re: HEGO ?

Unread postby blocmi » Thu Dec 19, 2019 8:48 pm

Sounds to me like you have an electrical issue on the passenger side to diagnose before you can tune anything.
Like I said, you can swap the O2 sensors from side to side to just rule the one out, but it sounds like you had this electrical issue prior to this engine.

I believe it is a very common issue. IIRC, many times its just a ground wire near the back of the motor that isn't hooked up... A good search of the interweb, and this website, should yield diagnosis and repair procedures.

When you fix it, you will see the numbers for HEGO1 will be constantly jumping above and below .400 volts like HEGO2 is.
blocmi
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Posts: 61
Joined: Wed Oct 03, 2018 4:41 pm
Location: New England
Name: Mike
Vehicle Information: 1995 Ford Mustang GT, 180K mile 302, CBAZA, U4P2, Quarterhorse, TunerPro RT, AEM WB, Ported GT40 Heads & Intake, E303, BBK 70MM TB, Cold Air Intake, 24lb Injectors, 80mm MAF, Adjustable FPR, FMS Headers, OR X-Pipe, C4 w/reverse manual valvebody, 3800-4100 stall converter, 4:10,


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