vacuum spec?

[97LowRanger]

hey guys i installed a vacuum gauge a while ago and it reads around 15 In Hg and with ac on it goes to around 13, my idle seems low its around 760-810 and with ac on it misses i have checked for vacuum leaks and found nothing, it lacks a little power i have cleaned the MAF and it got better but still seems to be weak, im thinking fuel pressure or ignition any other ideas? does anyone know the spec for vacuum? this is my daily driver so i need it to run better thanks!

 

[RonD]

Assume 2.3l engine?

And what altitude are you at?

Manual trans idle 700-750rpm
Automatic 800-850rpm

Most engines will be at 17"-20"
20" when new and 17" with lots of miles.

Piston rings and over all compression is what keeps vacuum high, assuming no vacuum leaks.
I would remove and plug the PCV hose and power booster hose just to see what vacuum is.

Also good read here on the tests and numbers: http://www.gregsengine.com/using-a-vacuum-gauge.html

 

[scotts90ranger]

My turbo engine at idle without anything going is 20-22" vacuum, so is my TIRED Geo Tracker (almost 300k on it), I would check your codes and such, but what's the vacuum at idle without the AC on?

 

[97LowRanger]

vacuum

without the ac on vacuum is at 13-14 in Hg it will not go higher than that, i have checked but i dont see or hear any vacuum leaks, i checked timing right on, checked spark all coils are good checked compression was surprised to see 165, 175, 175, and 182. so the only thing left i think is fuel maybe too much? maybe not enough to make it miss, i have no codes i have already cleaned the MAF, running out if ideas! 2.3 L 5 speed

 

[kimcrwbr1]

Have you checked ignition timing? Try adjusting the timing using the vacuum guage just a thought!

 

[kimcrwbr1]

You didnt say you checked the PCV system how old is the PCV and hose? Do not try and clean the PCV just replace it along with a good hose if it is hard or has loose ends.

 

[XLTsplash]

If your fuel trim is 0-12% you have a ignition caused misfire. If your fuel trim is above 20%. How many miles ago was your engines last tune up ? I would also inspect all you plastic vacuum lines, they break easy with age.

 

[97LowRanger]

so far..

ok guys i checked ig timing with a timing light and the crankshaft pulley mark is about 4 lines btdc i mean lines on the cover mark i dont know how many degrees that is, by looking it looks to be about 3/8ths btdc, checked my coils and they are good, had new wires and plugs about 6 months ago, pcv valve also, although it seems to leak or seap oil, i haven't checked the hose to pcv valve. i am going to check that and the evap canister hoses, and what do you mean check ignition with the vacuum gauge?
the truck has around 169xxx miles,and cold air intake.

 

[scotts90ranger]

He's talking about a vacuum advance distributor which you don't have

I'm thinking either vacuum leak (that's what my problem was, intake gaskets were toast on the bottom, hard to test...) or you have a metered air leak where air is getting in after the MAF. EGR could be sticking open causing a bunch of inert gas to be in the airstream...

 

[scotts90ranger]

What do you mean by cold air intake? like one of the hot air intakes the import guys use?

 

[97LowRanger]

What do you mean by cold air intake? like one of the hot air intakes the import guys use?

yes the "cold air intake" like you said hot air intake, and i had a problem a while ago and replaced the egr valve had a leak at the gasket there but fixed it, also replaced the vacuum solenoid for the egr and i forgot the name but its the vacuum valve for the egr its mounted nu the exhaust manifold close to the last plug. yes i do know i cannot adjust timing, so i have no other choice but to look for a vacuum leak, is there a way to test egr flow? also im going to check hoses to the charcoal canister, one of them is bad it breaks in my hand but its on the other side f the solenoids i will test the solenoids too and replace those hoses any other ideas? i'm pretty sure that its a leak. do you know where the main vacuum goes in/out to the ac actuators? i want to block it off to check if the leak could be because of an actuator even though all ac positions work, should i just remove the intake manifold? split and replace all gaskets?

 

[scotts90ranger]

The AC doesn't have vacuum related components (there is a heater valve that does though), the AC is just the clutch which is the 2 wire connector going in just behind the pulley on that pump, the vacuum difference with the AC on is because it is taking more power to idle than normal.

 

[XLTsplash]

You can spray carb cleaner or even water from a spray bottle [ safer because it's less flammable ] around areas that have vacuum on your engine with your engine running and listen for a change in idle speed. The liquid will temporarily seal the leak causing the idle speed to change. The vacuum line your looking for that goes inside the truck is black plastic and goes in under the blower motor housing. The the best way to test vacuum operated parts like vacuum actuators, egr valve, vacuum reservoir, lines and check valves is with a hand held vacuum pump. You can buy one at a auto parts store. They are a good tool to have around.

 

[97LowRanger]

yes i have done that i have sprayed the whole thing with water but dont see any leaks, at this point im sure there has to be one since my compression is really good all thats left has to be a leak, i will check till i find one! also to check the pcv valve do you have to remove the upper intake runners? i can barely see the hose so i think to check you have to remove it. also i have the hose from the valve cover to the intake tube it has a little bit of oil so im going towards the pcv valve and replacing it along with the hose anyways, its cheap so why not.

 

[XLTsplash]

You don't have to remove the upper intake to replace the PCV valve. It's a little hard to get to. It can be done. A power brake booster can also leak vacuum is your brake pedal harder to push than normal ?