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Related Vacuum Issues?

tobyw

Full Member
Joined
Jun 12, 2006
Messages
261
I've got two issues afoot here, and something tells me they might be related?

First off, when I depress the brake pedal at idle, the RPM changes... I'm guessing I've got a vacuum leak somewhere in the booster/fitting/hose?

Second, when I attempt to put the trans into gear (either Reverse or Drive), it does not immediately drop into gear, and sometimes takes several seconds to engage. It will also sometimes pop OUT of gear if I'm sitting with my foot on the brake (like at a stoplight). The selector has positive detents, but for some reason the tranny just doesn't seem to get/keep the info.

Are either/both of these vacuum issues? In my hasty overview, I'm not finding any vacuum leaks yet, but have not had the time to go very in-depth yet. Just fishing for ideas from those who have probably dealt with these issues before me ;D
 

ugly74

Bronco abuser
Joined
Apr 17, 2006
Messages
2,847
I'm not sure about the trans, but it sounds like your booster is leaking.
(cue the hydroboost crowd)
to see if that's what's buggin your trans, disconnect and plug the vac lines at the engine, and see how it shifts/holds in gear. (don't drive though)
and a dumb question maybe, but have you checked your trans fluid level?
 
OP
OP
tobyw

tobyw

Full Member
Joined
Jun 12, 2006
Messages
261
Fluid level is good (as long as my dipstick is marked correctly - looks factory??) and it's bright red, so I should be OK there...

How does one test a booster?
 

PaulS

Jr. Member
Joined
Dec 6, 2007
Messages
96
Loc.
Greater Seattle area
If you press on the brake pedal and hold it in one place the rpm should return to normal. if you move the pedal constantly you are bleeding vacuum in the valve and it should affect the idle.

Your tranny problem - I am assuming an automatic - is a linkage adjustment problem - at least it sounds like one to me.
If you have a C4 then you can adjust it easily by putting it in Drive with the engine off and hold it in the Drive position with a bungie cord holding it toward the "Second" geardetent in drive. Then get under the car and disconnect the shift linkage fron the transmission lever. make sure you have the transmission lever in Drive (three clicks from Park or two clicks from Low) and then adjust the linkage so it engages the lever without moving it at all.
Tighten things up and take it for a test drive.
 
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tobyw

tobyw

Full Member
Joined
Jun 12, 2006
Messages
261
I'll give that adjustment procedure a shot - thanks a bunch for the tip!

As for the booster, I've never had a vehicle that had an RPM affect from depressing the brake pedal, at least not so much that I've noticed... I'll have to verify whether or not it stabilizes with some time...
 
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