MAP Problems???? 90 plus KPA at Idle
11-01-2005, 11:33 AM
#1
Staging Lane
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MAP Problems???? 90 plus KPA at Idle The car is a heads, cam, converter, 42lb injectors, gear.
It will run fine while you are driving and all of a sudden it loses power and will die out if you hold the gas. At the same time we noticed the MAP was jumping up from around 40s to up to 90s. We replaced the MAP and its still doing it. Is there something done in the tune that could cause this or anything else? We are lost?
It will run fine while you are driving and all of a sudden it loses power and will die out if you hold the gas. At the same time we noticed the MAP was jumping up from around 40s to up to 90s. We replaced the MAP and its still doing it. Is there something done in the tune that could cause this or anything else? We are lost?
11-01-2005, 12:52 PM
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The MAP jump is indicating a gross drop in engine
efficiency. Almost certainly one of the three amigos,
air, fuel or spark is to blame.
If it's a single cylinder problem then the current
misfires ought to show you which. Plug wire,
single runner vacuum leak, silted up injector etc.
will all point the finger at one bad cylinder in the
current counts. If you're lucky the history may
have caught it too, saving you the trouble of
waiting for the next spasm.
You ought to also look at some of the sensors which
can drive fueling and spark, like the ECT which will
put you to some crazy places if it's intermittent (I
tuned on a truck once with a flaky connector, ECT
would jump from -40 to +300, and the spark was
freaking out right behind it.
efficiency. Almost certainly one of the three amigos,
air, fuel or spark is to blame.
If it's a single cylinder problem then the current
misfires ought to show you which. Plug wire,
single runner vacuum leak, silted up injector etc.
will all point the finger at one bad cylinder in the
current counts. If you're lucky the history may
have caught it too, saving you the trouble of
waiting for the next spasm.
You ought to also look at some of the sensors which
can drive fueling and spark, like the ECT which will
put you to some crazy places if it's intermittent (I
tuned on a truck once with a flaky connector, ECT
would jump from -40 to +300, and the spark was
freaking out right behind it.
11-01-2005, 01:57 PM
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Staging Lane
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Ok I also forgot to add that it had a Z06 MAF also
heres what happens, I drive it out of the driveway, down the street and boom it cuts off if you hold your foot on the pedal and it will only run if you let off the pedal. Then the SES light comes on and heres what I get
P0101 - Mass Air Flow (MAF) Sensor Performance (SES) (Pending) (History) (Immature)
P0101 - Mass Air Flow (MAF) Sensor Performance (SES) (Pending) (History) (Immature)
P1133 - HO2S Insufficient Switching Bank 1 Sensor 1 (OLD) (Current) (Immature)
P1153 - HO2S Insufficient Switching Bank 2 Sensor 1 (OLD) (Current) (Immature)
heres what happens, I drive it out of the driveway, down the street and boom it cuts off if you hold your foot on the pedal and it will only run if you let off the pedal. Then the SES light comes on and heres what I get
P0101 - Mass Air Flow (MAF) Sensor Performance (SES) (Pending) (History) (Immature)
P0101 - Mass Air Flow (MAF) Sensor Performance (SES) (Pending) (History) (Immature)
P1133 - HO2S Insufficient Switching Bank 1 Sensor 1 (OLD) (Current) (Immature)
P1153 - HO2S Insufficient Switching Bank 2 Sensor 1 (OLD) (Current) (Immature)
11-01-2005, 02:18 PM
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What year is this car? Old enough that it used to have
the LS1-style "Oreo" MAF? If so was it retuned for the
Z06 calibration?
The MAF performance code indicates the speed density
and the MAF airflow values are in disagreement. Idle is
almost entirely speed density and apparently happy.
A Z06 MAF would put a LS1-style 75mm tuned car
very rich. The O2 switching codes will make the PCM
go open loop and quit trying to correct for it, which may
be the point where things abruptly go to ****. Is this
anything like the situation?
the LS1-style "Oreo" MAF? If so was it retuned for the
Z06 calibration?
The MAF performance code indicates the speed density
and the MAF airflow values are in disagreement. Idle is
almost entirely speed density and apparently happy.
A Z06 MAF would put a LS1-style 75mm tuned car
very rich. The O2 switching codes will make the PCM
go open loop and quit trying to correct for it, which may
be the point where things abruptly go to ****. Is this
anything like the situation?
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11-01-2005, 02:55 PM
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Agree with jimmyblue, see what happens when you put the car in SD mode by putting a 0 in the MAF Fail freq. And see how it runs then, if so your MAF calibration is horribly off and needs to be tuned.
Dixit
Dixit
