Solved: Hard vacuum leak under DECELERATION
- Thread starter STI_MECE
- Start date
brillo_76
Elite Member
I would think the strongest place for vacuum would be your intake manifold.
Dont you have a bluetooth code reader? As that with an app like torque pro will give you vacuum readings so you can test in real time going down the road.
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STI_MECE
New member
I have bluedriver app. I don't think the one I got supports reading vacuum.
Here is cold start
Here is warmed up.
Pulling the throttle body several times and quickly it would jump to zero then go to about 24 ish before going back down to 21.
Why would it want to pull more vacuum whenever I briefly open and close the throttle body for like a 2k rev up?
Is there such a thing as too much vacuum lmao
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Here is cold start
Here is warmed up.
Pulling the throttle body several times and quickly it would jump to zero then go to about 24 ish before going back down to 21.
Why would it want to pull more vacuum whenever I briefly open and close the throttle body for like a 2k rev up?
Is there such a thing as too much vacuum lmao
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STI_MECE
New member
Now I would like to pull a vacuum on the engine and test for leak's but vacuum is vacuum.....
But I mean shouldn't I be seeing the same values when driving right? I mean I can't pull more vacuum than what the engine can self generate whenever the throttle body is closed.
Im thinking about taking the hood off and just running the hose inside the truck so I can see the gauge lol
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But I mean shouldn't I be seeing the same values when driving right? I mean I can't pull more vacuum than what the engine can self generate whenever the throttle body is closed.
Im thinking about taking the hood off and just running the hose inside the truck so I can see the gauge lol
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brillo_76
Elite Member
For the love of God.. At least your having fun. Merry Christmas.
Yes the vaccuum should be really close to gauge vs measured.
Take some photos of your slay driving your hood off. Maybe you can throw candy at the neighborhood kids. [emoji14]
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Yes the vaccuum should be really close to gauge vs measured.
Take some photos of your slay driving your hood off. Maybe you can throw candy at the neighborhood kids. [emoji14]
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brillo_76
Elite Member
Think about this for a second. You have a straw your sucking on. Now all the sudden this straw is 10x larger for a second then back to normal size again. That's what your seeing in the vaccuum. That zero is the open throttle body and that brief higher vacuum is the demands of the high throttle position before return back to normal vacuum at idle. Engines aren't instantly able to respond.I have bluedriver app. I don't think the one I got supports reading vacuum.
Here is cold start
Here is warmed up.
Pulling the throttle body several times and quickly it would jump to zero then go to about 24 ish before going back down to 21.
Why would it want to pull more vacuum whenever I briefly open and close the throttle body for like a 2k rev up?
Is there such a thing as too much vacuum lmao
Sent from my Pixel 3 XL using Tapatalk
I turn on my torque pro app and record for a day or so then send you the results so you can see what the vaccuum is doing.
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STI_MECE
New member
It's not the vacuum that is confirmed now
It might be my drive shaft. And go down there and try to turn it and there is a small, and I mean very tiny in that front u joint I guess you call it
I have to grab the middle of the driveshaft and try and rotate it and sure enough there is a tiny tiny amount of play in that joint.
I ended up doing this all on jacks. But I put the gauge inside the truck as I drove and the vacuum didn't change one bit.
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It might be my drive shaft. And go down there and try to turn it and there is a small, and I mean very tiny in that front u joint I guess you call it
I have to grab the middle of the driveshaft and try and rotate it and sure enough there is a tiny tiny amount of play in that joint.
I ended up doing this all on jacks. But I put the gauge inside the truck as I drove and the vacuum didn't change one bit.
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19963.4lsr5
New member
Hard vacuum leak under DECELERATION
If your vacuum gauge is plugged into the intake manifold it will change with throttle position. Highest vacuum is at idle and decell.
The vacuum on torque is calculated. Our fuel is based on a MAF sensor not a MAP sensor.
Edit: Torque tells me I have 25inhg at idle. I don’t believe it. I do believe 22 or close to it.
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If your vacuum gauge is plugged into the intake manifold it will change with throttle position. Highest vacuum is at idle and decell.
The vacuum on torque is calculated. Our fuel is based on a MAF sensor not a MAP sensor.
Edit: Torque tells me I have 25inhg at idle. I don’t believe it. I do believe 22 or close to it.
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Last edited:
STI_MECE
New member
Took to transmission shop for second opinion they are thinking it might be the carrier bearing? If I am saying that right....he wanted 450 just to inspect it but he did say he would recommend taking a 3rd member from another 4runner and dropping it in.
Decisions....
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Decisions....
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brillo_76
Elite Member
Oh. You didn't know what a universal and bearing sounds like.
Did you hit the zerk fittings with grease. [ If any exist on 2WD] Being your not in the rust belt and that 3rd member never ran low or out of gear grease.
I would verify your universals are good. Our lower ones are prone to failure when mileage gets up there if not greased. Being your if 2wd. You probably dont have grease fittings in your universals.
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Did you hit the zerk fittings with grease. [ If any exist on 2WD] Being your not in the rust belt and that 3rd member never ran low or out of gear grease.
I would verify your universals are good. Our lower ones are prone to failure when mileage gets up there if not greased. Being your if 2wd. You probably dont have grease fittings in your universals.
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19963.4lsr5
New member
Oh. You didn't know what a universal and bearing sounds like.
Did you hit the zerk fittings with grease. [ If any exist on 2WD] Being your not in the rust belt and that 3rd member never ran low or out of gear grease.
I would verify your universals are good. Our lower ones are prone to failure when mileage gets up there if not greased. Being your if 2wd. You probably dont have grease fittings in your universals.
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My 96 and both 97’s had grease fittings on every universal.
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19963.4lsr5
New member
No grease fittings on either end
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They would be inside the cross if they were there. They may be caked with dirt and not visible.
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brillo_76
Elite Member
4wd have fittings 2WD do not. You can change the 2WD universals to 4WD so you can grease them.
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brillo_76
Elite Member
How to check universals.
1)Jack up the wheels on the axle you want to check. ( make you block the other axle) and put on jack stands.
2) Once all secure. Get under there and shake the driveshaft to see if you see any movement.
3) If any movement the universal is done.
4) Rotate the driveshaft by turning it or a tire. Check all 4 cups. Even one cup bad will make noise and Junk. You see if move in the cup if the needle bearings are failing universal junk.
I would suspect either universal way before the rear end or tail shaft. However, they could go too. I would just super verify those are good before looking at anything else.
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1)Jack up the wheels on the axle you want to check. ( make you block the other axle) and put on jack stands.
2) Once all secure. Get under there and shake the driveshaft to see if you see any movement.
3) If any movement the universal is done.
4) Rotate the driveshaft by turning it or a tire. Check all 4 cups. Even one cup bad will make noise and Junk. You see if move in the cup if the needle bearings are failing universal junk.
I would suspect either universal way before the rear end or tail shaft. However, they could go too. I would just super verify those are good before looking at anything else.
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Dieselchessy
New member
I’ve had pinion bearings go that started by howling when loaded on deceleration (engine braking).
They made the typical bad bearing growl type noise though.
They made the typical bad bearing growl type noise though.
