goes lean during cruise
11-06-06, 04:45 PM
#1
goes lean during cruise
i have a s4 TII. i noticed sometimes when cruising at around 2k-3k rpms in like 15" of vac i get a really lean condition. jumps from 14A/f to sometimes 17A/F! then a sec or two later it goes away and A/F drops back down to normal. i dont know why its doing it. any thoughts?
fuel filter was changed bout 3 or 4 months ago (only use 93 octance)
have a fd fuel pump
have tried 3 different ecus and the samething
replaced TPS still the same
i have a crane cam high on leading coil (maybe has something to do with it?)
removed emissions but keep twin scroll (" ")
fuel filter was changed bout 3 or 4 months ago (only use 93 octance)
have a fd fuel pump
have tried 3 different ecus and the samething
replaced TPS still the same
i have a crane cam high on leading coil (maybe has something to do with it?)
removed emissions but keep twin scroll (" ")
11-06-06, 11:18 PM
#4
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Seems if the 02 was connected and you were cruising, then the ECU would go into closed loop and pull those 15afr figures down to the 14.7 afr area.
I've no idea why then your afr go that lean. SAFC leaned out too much?
I've no idea why then your afr go that lean. SAFC leaned out too much?
11-07-06, 07:14 AM
#6
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Is it during slight downhills, or where very very little throttle is needed? because there is a spot where it cuts fuel to the rear rotor. This may cause a very lean reading?
11-07-06, 07:28 AM
#7
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Just a thought, have you done the fuel pump mod? try checking the voltage to the pump at low rpms it could be that your not getting enough voltage to the pump. Our cars are old and so is everything in them ( wires included :b). I had this problem twise before first time was a bad fuel pump, second time was a wrong setting on my SAFC II.
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11-07-06, 07:42 AM
#9
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My TII does the exact same thing. Only thing I haven't tested or replaced is the AFM. To the best of my knowledge the rear rotor has fuel cut at the rev limiter.
11-07-06, 08:16 AM
#10
Originally Posted by JBrotor
My TII does the exact same thing. Only thing I haven't tested or replaced is the AFM. To the best of my knowledge the rear rotor has fuel cut at the rev limiter.
wat else have you tried?
11-07-06, 02:06 PM
#14
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Originally Posted by Aaron Cake
It's likely a misfire. Check the condition of your plugs/wires.
Don't worry about it though...Only an issue under boost.
Don't worry about it though...Only an issue under boost.
xboxthug13b,
I have checked plugs, wires, TPS (cleared it up a little), and Vacuum leaks.
11-07-06, 04:35 PM
#15
So a misfire would cause the A/F to jump up? Lean under vac is good but not when it jumps up suddenly and goes back down!
I have replaced plugs aaron cake but not wires yet, ill be doing that next.
If I remeber correctly (gotta recheck) narrow band would read full rich I think.
I have replaced plugs aaron cake but not wires yet, ill be doing that next.
If I remeber correctly (gotta recheck) narrow band would read full rich I think.
11-08-06, 09:18 AM
#18
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Attached is a jpg of a Palm connected to a Zeitronix wideband.
The car is in fifth gear and the 02 sensor is connected up.
In the left hand display it shows AFR. Just under the AFR you see two figures. One is the high and one is the lowest afr while cruising and the 02 in closed loop.
Make of it what you will.
The car is in fifth gear and the 02 sensor is connected up.
In the left hand display it shows AFR. Just under the AFR you see two figures. One is the high and one is the lowest afr while cruising and the 02 in closed loop.
Make of it what you will.
11-08-06, 06:01 PM
#22
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If you have a RTEK 2.0, then if you go to the Diagnostic page, it will show if you have a failed 02 sensor. I know that because I did that on my car the other day just to check it out with your figures and sure enough it showd the 02 not connected.
Bad workmanship on yours trulys part. Done did pull that wire flat intwo sometime. When? Got me.
That said, I had a problem with my other car with high afr during steady state driving. So I found if I went to the fuel bars and added fuel to the MINUS boost figures (like minus 2, minus 4, minus 6) for the first three bars, then that high afr at steady rpm went south.
Bad workmanship on yours trulys part. Done did pull that wire flat intwo sometime. When? Got me.
That said, I had a problem with my other car with high afr during steady state driving. So I found if I went to the fuel bars and added fuel to the MINUS boost figures (like minus 2, minus 4, minus 6) for the first three bars, then that high afr at steady rpm went south.
11-25-06, 10:33 AM
#25
and now sometimes when i floor it the car bogs and then takes off, also my 3800 transistion isnt smooth at all (maybe because of bigger secondarys?) i have reground the grounds, cleaned ground on batter, starter and the one by strut tower.
Last edited by AlexG13B; 11-25-06 at 10:42 AM.