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Hi

Testing the map sensor, using vacumm gauge. First time doing so. Trying to see if map sensor is working correctly.
No error codes prior.

Idles smooth between 22 and 24 inHg by pumping the handle. Stop pumping handle and vacumm decreases all the way down to zero, then engine cuts off.

Video attached. https://youtube.com/shorts/JywVRFCO394?feature=share

Any help is appreciated

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.

I have no idea what inches of vac means but a healthy VN-VR v6 should idle around 20 Kpa absolute assuming the tune is optimal at idle.

vlad01 wrote:I have no idea what inches of vac means but a healthy VN-VR v6 should idle around 20 Kpa absolute assuming the tune is optimal at idle.

Hiya vlad,
inches is just another type of measurement. Kpa is metric and inches is american. Then there is inches of mercury and inches of water
Holley power valves are rated in inches, still don't know if it is inches of mercury or inches of water. On the circle track race cars I just datalog the map sensor and wideband(amongst other things) then watch when power enrichment occurs and adjust accordingly.

There's approx 7.5mmHg per kPa
so 1" Hg is 25.4/7.5 = 3.386kPa
20"Hg is then 101.3kPa - (20 * 3.386) = ~ 33.6kPa Absolute

30-32 kpa is about where my cam'd VP runs with 212/212 and 109 LSA. Stock should be 20 ish kpa and pull down to about 12-15 kpa on throttle snap shut.

And if we look at the OPs numbers of 22 - 24" that equates to 26.8kPa - 20kPa.
So if the engine runs nicely when you are applying a vacuum level that is close to the expected idle value for a stock motor, it sounds as if the sensor itself is ok.

From my experience to get a reading of 24 your timing is well advanced. Most cars are 20-21 if the engine is in good condition.

Hiya Folks,
20 kpa at idle is an incredible amount of vacuum and I don't think I have ever seen that on stock vehicles. From memory, it seems they are 30-35 kpa in neutral/park. I have a stock 6L LS coming in tomorrow for a tune. I will play with rpm and report kpa values. Shoot I have tuned some nasty marine stuff that idled at ~87 kpa in neutral and went into boost when dropped in gear. Those are fun to tune

They have tiny stock cams though, 181/191 and 111 LSA and if I recall negative overlap.