Something weird going on
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From: Pittsburgh, PA
Something weird going on I will be driving in 6th gear at 1800 rpm down the parkway keeping the speed constant. All of a sudden I will feel the car bog down and I look at my A/F gauge and it pegs lean. I let my foot off the gas and back on and it is fine. It might drive fine for 5 minutes or so then it will happen again. None of the cells in my table are that far off. I replaced the MAF thinking it was doing it but it still happens. Could an O2 cause this??? It only happens while cruising at a constant speed in high gear
A Google response:
Inspect for the following conditions:
An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:
- The secondary ignition wires or coils
- Any solenoids
- Any relays
- Any motors
A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.
A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 230 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
The barometric pressure (BARO) that is used in order to calculate the predicted MAF value is initially based on the MAP sensor at key ON.
When the engine is running the MAP sensor value is continually updated near WOT. A skewed MAP sensor will cause the calculated MAF value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
A high resistance on the ground circuit of the MAP sensor can cause this DTC to set.
Any loss of vacuum to the MAP sensor can cause this DTC to set.
Inspect for the following conditions:
An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:
- The secondary ignition wires or coils
- Any solenoids
- Any relays
- Any motors
A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.
A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 230 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
The barometric pressure (BARO) that is used in order to calculate the predicted MAF value is initially based on the MAP sensor at key ON.
When the engine is running the MAP sensor value is continually updated near WOT. A skewed MAP sensor will cause the calculated MAF value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
A high resistance on the ground circuit of the MAP sensor can cause this DTC to set.
Any loss of vacuum to the MAP sensor can cause this DTC to set.
Thread Starter
Restricted User
iTrader: (43)
Joined: Nov 2001
Posts: 2,669
Likes: 1
From: Pittsburgh, PA
I sealed the map sensor since they are very secure in the FAST Intakes. Took it for a ride and the same thing happened. Stead pedal pressure at low rpm and then wham full lean until I varied the pedal pressure. The MAF and MAP seemed to be fine and were reading correctly.
Wonder if this is something like a misfire, making
the O2s read lean. Is misfire detection still in place?
Can you see anything in the dynamic airflow number
across the start-of-problem, in the injector pulse
width? Need to figure whether it's a change to the
air/fuel at the "input side" or just reading crap when
the event takes place.
The MAF code might be indicating some degree of
inconsistency between the speed-density and the
MAF airflow numbers, maybe when it faults it goes
and picks the wrong one to listen to.
Might also want to look at the delivered spark
advance, make sure it's not being jacked to the
point that incomplete combustion occurs.
the O2s read lean. Is misfire detection still in place?
Can you see anything in the dynamic airflow number
across the start-of-problem, in the injector pulse
width? Need to figure whether it's a change to the
air/fuel at the "input side" or just reading crap when
the event takes place.
The MAF code might be indicating some degree of
inconsistency between the speed-density and the
MAF airflow numbers, maybe when it faults it goes
and picks the wrong one to listen to.
Might also want to look at the delivered spark
advance, make sure it's not being jacked to the
point that incomplete combustion occurs.
