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toy. truck-possible vaccuum prob.
10-04-2008, 11:00 PM
Post: #1
toy. truck-possible vaccuum prob.
got 91 toy. pickup-engine is 4cyl-fuel inj. just replaced brake booster cause when u step on the brake the engine would groan / say every 20 seconds or so.when foot comes off brake truck would run fine! got new booster on made no diiference. i have no idea ,but it still does it every time u step on brake,and occasionally when i start it up does it while its idling and not touching brake!! when u put ur hand on ;air cleaner housing ,while idiling it feels like back pressure going back to air filter--any way were stumped! any advice?????----5buck
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10-04-2008, 11:24 PM
Post: #2
RE: toy. truck-possible vaccuum prob.
Try replacing the check valve or the vac line going to the booster along with the other vac lines.

I have seen old lines get soft from age or oil over the years and they can make the strangest sounds.
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10-04-2008, 11:50 PM
Post: #3
RE: toy. truck-possible vaccuum prob.
Rupe Wrote:Try replacing the check valve or the vac line going to the booster along with the other vac lines.

I have seen old lines get soft from age or oil over the years and they can make the strangest sounds.
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10-04-2008, 11:59 PM
Post: #4
RE: toy. truck-possible vaccuum prob.
ya took the check valve off first ,blew through it ; air would only blow 1 way ,from the booster to the air chamber so i assumed it was ok ,and the hose at least on the booster is in good shape! i;ll check the rest of them, but i think something else is going on. seems like air supply is being cut -off intermittently.but like i said it always does it while brake is depressed. thanks for your time rupe!
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10-05-2008, 12:14 AM
Post: #5
Cool RE: toy. truck-possible vaccuum prob.
oh ya probably should have mentioned i replaced the timing chain,cover and head gasket about a year ago,and to do all that the valve cover had to come off! what a project! the only reason that was replaced i had antifreeze in the oil pan,the guides on the sides of timing chain had broken and the chain was rubbing on the inside of the water pump housing,hence the a-freeze in the oil pan-i guess thats a common prob. on toyotas-any way when i took the valve cover off i labeled all the vaccuum lines for re-install, but i could have misplaced 1 or 2 i guess-besides this problem it runs real good,thanks again-5buck
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10-05-2008, 11:53 AM
Post: #6
RE: toy. truck-possible vaccuum prob.
Not sure if your truck is old enough but years ago both Nissan and Toyota use something called a BCDD (Boost Controlled Deceleration Device) and it was tied into the bottom of the air cleaner housing with a couple of large vac hoses. This device was used to hold down emissions on deceleration via creating a LARGE vac leak. Basically the idea was if vac was reduced then the rich mix on deceleration would be avoided and therefore emissions reduced. It was the better mouse trap for many years but they do go bad. I'm recalling these were problematic on the carb vehicles but don't recall if they carried into the early injected engines.

What I would do is go around the engine compartment with a long nose pliers and one at a time pinch off vac lines till you figure out which one is causing the issue, then identify the component and or replace the vac hose as the problem dictates.
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10-05-2008, 12:00 PM
Post: #7
RE: toy. truck-possible vaccuum prob.
im gonna do that today, ithink that might b the problem--thanks rupe you rock!!
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