Map sensor KPA decreases as I accelerate
08-06-2018, 12:43 PM
#1
Map sensor KPA decreases as I accelerate After about 2800 rpm, my MAP sensor KPA goes down as I accelerate causing a lean condition up top. No MAP codes. I have a new FAST 102 intake, new 102 TB, and I had installed a new MAP. I just installed a second MAP and it's still doing it.
Last edited by Gripenfelter; 08-06-2018 at 02:26 PM.
08-06-2018, 06:32 PM
#4
TECH Senior Member
Definitely use the Delphi or AC/Delco unit. Off brand units are known to be of questionable quality.
08-06-2018, 08:40 PM
#6
Key on. Car off it’s at 14.3.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
08-07-2018, 06:49 AM
#7
it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA
Definitely try a different one - maybe a "known good used" first - before anything else.
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08-07-2018, 09:04 AM
#8
Key on. Car off it’s at 14.3.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
08-07-2018, 10:04 AM
#9
Restricted User
Are you holding constant throttle while this happens?
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
08-07-2018, 10:43 AM
#10
Key on. Car off it’s at 14.3.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
08-07-2018, 01:17 PM
#11
Key on. Car off it’s at 14.3.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
I don’t go WOT but at 26% throttle in second gear it goes up to about 70 KPA and then after 2800 rpm starts to drop off where close to 4000 rpm it’s at 35 KPA. Goes super lean so I don’t go WOT. Under 3000 rpm it’s fine.
Harness is correct. Just checked.
Are you getting 5 volts to the MAP sensor in the harness? You should have 12v, 5v and ground on the three wires going to the MAP. Check to make sure you are getting the correct voltages through the harness with the key on ignition off. Check the main harness voltages/continuity and then add the extension harness and check that as well for the same readings. If you have the correct voltages, then I would replace the MAP sensor. The only other thing that could be wrong would be the 5 volt step down transformer in the PCM.
Not 2 powers and a ground.
08-07-2018, 05:01 PM
#12
Key on engine off KPA should be close to 100 kpa, 100 kPa is 1.0 bar which is atmospheric pressure. Not sure where you are so not sure of your exact baro pressure, but here in Dallas it's usually 29.5-29.9 range when I check it. See if you have a baro pid in your data stream and compare it to your area's baro pressure. However 14.3 kPa is 45,000 ft altitude
5 volt, ground, and signal return
Not 2 powers and a ground.
5 volt, ground, and signal return
Not 2 powers and a ground.
08-07-2018, 06:20 PM
#14
Are you getting 5 volts to the MAP sensor in the harness? You should have 12v, 5v and ground on the three wires going to the MAP. Check to make sure you are getting the correct voltages through the harness with the key on ignition off. Check the main harness voltages/continuity and then add the extension harness and check that as well for the same readings. If you have the correct voltages, then I would replace the MAP sensor. The only other thing that could be wrong would be the 5 volt step down transformer in the PCM.
Are you holding constant throttle while this happens?
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
Key on engine off KPA should be close to 100 kpa, 100 kPa is 1.0 bar which is atmospheric pressure. Not sure where you are so not sure of your exact baro pressure, but here in Dallas it's usually 29.5-29.9 range when I check it. See if you have a baro pid in your data stream and compare it to your area's baro pressure. However 14.3 kPa is 45,000 ft altitude
5 volt, ground, and signal return
Not 2 powers and a ground.
5 volt, ground, and signal return
Not 2 powers and a ground.
08-14-2018, 04:43 AM
#19
Are you holding constant throttle while this happens?
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
If you are, that's exactly what is supposed to happen. At part throttle, your able to feed more air than the engine needs, kpa will be high.
As RPM goes up, that partial throttle opening is supplying a smaller % of the air that the engine needs. KPA will drop as vacuum increases in the intake.
You can pull the MAP down to 25 KPA if you let off the throttle at 5000 RPM.
08-14-2018, 07:10 AM
#20
I would hold constant throttle but it would actually go super lean.
I think i might have fixed it though. It was leaking pressure out through the oil catch can because there was no stop valve in there. Put it in. Seems way better. I’ll do a log tonight.
I think i might have fixed it though. It was leaking pressure out through the oil catch can because there was no stop valve in there. Put it in. Seems way better. I’ll do a log tonight.