Testing MAP sensor with vac gauge - due to rough idle

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby vlad01 » Fri Sep 16, 2022 6:50 pm

My bad, 25-30 for stock and high 30s-low 40s for my cam'd engine when I checked back at the logs, I mistaken the vac when part throttle revving in N. There is pulls 20 for stock and mid to high 20s for the cam'd engine and below 10 kpa for both when the throttle snaps shut.
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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby antus » Fri Sep 16, 2022 7:56 pm

I dont think hooking the map sensor up to a different source of vaccume to what the engine sees, then measuring results by the quality of idle is a valid test. If you want to test the map sensor key on with the engine not running and check that the pcm is reporting close to 100kpa for atmospheric pressure. then hook up the pump and guage and check the pcm is reporting the same kpa you are seeing on the guage as you change it. If values are close, the map is ok and look for the problem elsewhere.
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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Pete30nz » Sun Sep 18, 2022 9:50 am

Charlescrown wrote:What maniflod vacuum do you get @ idle? should be around 20 inches. Also is your vac pump reading accurate? The more vacuum you apply the leaner the fuel mix gets so maybe it's running rich for some reason. If you have somethnig like TunerPro you should get a map reading of 101kPa key on engine off.

Hi charlscrown, on idle via the fuel reg vac port it was sitting about 21 inHg.
This is the first ever vac gauge I've ever had, I don't know how to check it.

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Pete30nz » Sun Sep 18, 2022 10:02 am

Hi there ,all that commented, I'm loving the input :thumbup: Looks like I have a better way to test the sensor. I did also start a vacuum thread, in saying this I will get around to doing the can of spray trick around the intake to check for a possible leak? While doing this, listening for a smooth idle upon spraying Carby cleaner I guess?

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Charlescrown » Sun Sep 18, 2022 12:04 pm

21 is a good reading for a NA engine in good condition. Turbo usually a tad lower if they have lower compression ratio. So if the engine gets smoother as the vac increases your running too rich particularly with an engine like yours.

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Pete30nz » Sun Sep 18, 2022 7:02 pm

I have taken a few logs of sensor data, I'll have to post those from the laptop though. It has new plugs, leads, and have checked for good spark with spark tester, all strong looking spark. It also has a new oxygen sensor.
What else can cause it to run rich?

Today I sprayed Carby cleaner around the edge of the intake manifold, there mite of been a smooth idle, but I didn't have the vacuum gauge attached to look at.

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby antus » Sun Sep 18, 2022 7:46 pm

what kpa did it read with the key on but the engine not running? when it warms up what does the o2 sensor read?
Have you read the FAQ? For lots of information and links to significant threads see here: viewtopic.php?f=7&t=1396

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Pete30nz » Mon Sep 26, 2022 12:55 pm

hi there, taken some logs today. will attach below.

The kpa reading mite be on the sensor data. I havn't had the vac gauge hooked up today.

reading and logging files im using the following:
Holden VR V6
XDF $11B_V106.xdf
ADX VR_$11_v1.05-tp5.adx

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Attachments
key in on position - sensor data.png
sensor data gauges - key in on position.png
few minute drive up the road, while engine at running temp.xdl
(173.04 KiB) Not downloaded yet
cold start today monday 26 105pm.xdl
(104.67 KiB) Not downloaded yet
restarted car then engine settled rough idle and sat at 740 revs.xdl
(13.14 KiB) Not downloaded yet
at running temp o2 is in red numbers.xdl
(12.76 KiB) Not downloaded yet

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby Charlescrown » Mon Sep 26, 2022 2:31 pm

A quick look at your map sensor shows it's a tad high. Should be 101 @ sea level and get lower with altitude but I doubt that small amount would have an effect.

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Re: Testing MAP sensor with vac gauge - due to rough idle

Postby vlad01 » Mon Sep 26, 2022 4:29 pm

That's a known bug, at least with 12P and 11P. Baro is somewhat random but in the ball park. I always get between 101 and 104 even though it's not possible living at 95 Kpa above sea level. MAP always shows the correct 95 Kpa but Baro always shows 100+ no matter what. VL400 claimed to had fixed this years ago with the ADX when I reported the bug but it still exists, so I suspect it's somewhere in the factory code and worked it's way into 11 and 12P as well.

I even tested it at 1 Km above sea level which is I think 88-89 Kpa but still reported the Baro to be 103 or similar, as a result with my worked engine the CEL for rich O2 was triggered by it while on the mountain, but is fine when at more normal elevations.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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