4.6 Vacuum Question
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From: New Mexico
4.6 Vacuum Question
I'm wondering if anyone can tell me what the normal vacuum reading should be at idle for the big hose and small hose the comes off behind the throttlebody on the passenger side for a vehicle with 100k miles.
I believe my book says 17-20.
I believe my book says 17-20.
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From: Long Island USA
Check all the usual things. Clean the MAF, change the fuel filter, change the air filter too if it hasn't been done 
If you can get your hands on a fuel pressure gauge, check the fuel pressures.
With the key-on, engine-off, pressure should be around 40. With key-on, engine idling, it should be around 28-30.
If you have a long enough hose for it, check what it is when you think it's sluggish. And report back
If you can get your hands on a fuel pressure gauge, check the fuel pressures.
With the key-on, engine-off, pressure should be around 40. With key-on, engine idling, it should be around 28-30.
If you have a long enough hose for it, check what it is when you think it's sluggish. And report back
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From: New Mexico
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From: Louisville,Ky.
Where are you getting your vacuum signal from. At steady speeds you should have close to 15 or better. At WOT you should have 0. Check the PCV hose elbows for cracks and leaks. Especially where it hooks to the back of the intake.
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From: Long Island USA
That's strange... I T'd into the brake booster line. Nice big fat hose...
It looks like the right spot you got, just after the throttle body.
Check for leaks like Jimmy said, he's spot on
It looks like the right spot you got, just after the throttle body.
Check for leaks like Jimmy said, he's spot on
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From: New Mexico
update.
Changed pcv valve,
sea foamed intake,
sea foamed gas tank,
tested egr valve with vac, worked normally,
sprayed MAF with electrical cleaner,
Fuel filter looks new, so i didn't change it yet.
THinking about popping out my front O2 sensors and seeing if vacuum increases.
I'm a little leary of spraying starting fluid around my engine to spot vacuum leaks. lol
I drove to town today on a fairly flat road. With cruise set at 55, I was between 0-4 vacuum.
Changed pcv valve,
sea foamed intake,
sea foamed gas tank,
tested egr valve with vac, worked normally,
sprayed MAF with electrical cleaner,
Fuel filter looks new, so i didn't change it yet.
THinking about popping out my front O2 sensors and seeing if vacuum increases.
I'm a little leary of spraying starting fluid around my engine to spot vacuum leaks. lol
I drove to town today on a fairly flat road. With cruise set at 55, I was between 0-4 vacuum.
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From: New Mexico
I am running 32" tires. Seems like the tranny has to work really hard to keep this boat moving, almost like it is pulling a heavy trailor.
No OBD2 codes to speak of.
I noticed one of the hoses from the evap service port on the firewall goes behind the engine somewhere. THe other one is just hanging out not attached to anything. It doesn't have any vacuum going thru it.
It looks like it should attach behind the throttlebody but someone unhooked it and put a cap over the outlet.
No OBD2 codes to speak of.
I noticed one of the hoses from the evap service port on the firewall goes behind the engine somewhere. THe other one is just hanging out not attached to anything. It doesn't have any vacuum going thru it.
It looks like it should attach behind the throttlebody but someone unhooked it and put a cap over the outlet.
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From: Long Island USA
Sounds like someone cut off the evaporative recovery...
Weird that you have that low vacuum...
I run 15 inches on the highway. And most other engines I've had vacuum guages on were about 14-15.
Just for grins, can you hook it into the line going to the brake booster?
Weird that you have that low vacuum...
I run 15 inches on the highway. And most other engines I've had vacuum guages on were about 14-15.
Just for grins, can you hook it into the line going to the brake booster?
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From: Louisville,Ky.
That is normal. When you just rev it, the vacuum drops. The farther open that the throttlebody is, the less manifold vacuum that you will read.
You could possibly have a converter trying to clog up. Most exhaust shops will check them for free.
You could possibly have a converter trying to clog up. Most exhaust shops will check them for free.