Howdy everyone,
So I am looking for some advice from some of the pros's out there. I was driving around and I hear is "gingleing" from the front passanger area, thinking it might be a loose brake pad. So I keep my foot on the throttle and slowly apply the brakes, suddenly the RPM's spike up 250 RPM's!!!! Thinking it was me advert entry pushing harder on the accelerator, I repeated this process, over and over again with the same results, the RPM's spike about 250 RPM's. I did this over several RPM ranges from low to high, and the same results every time.
I am wondering if there is something inside the brake booster that is causing a vacuum leak, resulting in the spike in RPMS. I did check the vacuum line off the brake booster and it looks fairly new, the only thing odd was the hose was slid down the nipple on the booster maybe 1/2" but not to the barbs.Please let me know you thoughts on this issue....
Ants everyone,

 

Sounds like the diaphragm inside the booster is broke. It's about a 8" diameter disc of sheet rubber. About the same thickness and whatnot as a bicycle tire inner tube.

Pretty much, that's how they fail. They crack either at the center (where the push rod attachment is) or around the edge.

You need a booster.

 

Thanks for chiming in Sofa... My only concern is why don't the RPM's change any other time? The brakes feel great and stops the car on a dime with 0.09 change... I do have a rough idle, but I also noticed a dry rotted hose off the fuel pressure regulator

 

Because at no time does the vac diaphragm move, other than when you push the brake pedal.

See my signature for a logical trick that speeds up troubleshooting DRAMATICALLY.

If you see other problems as well, FIX THEM. Won't fix the brake problem but doesn't make much sense to expect your car to work right when you KNOW there's stuff that's messed up.

 

OH I TOTALY get that Sofa... I'm going to get the old vac lines changed, at least what I can see, but my charcoal canister seams a bit confusing.
Back to the RPM spike, did I mention it only did it when I was accelerating, when driving normal the only fluxuation is 3/4 throttle and right back to idle, then RPM's drop below idle then above idle then back down to idle. So it is odd that the RPM spike only happens when I am accelerating.

 

Just throwing this out, but aint that just the converter lockup?

Tap the brake, converter unlocks, rpm increases 100-300 rpm, off the brake converter locks and rpm drops back down? Sounds like normal converter lock-up to me.

 

Yes, there is also that... although that would only happen in the high gears (not "all"), and should result in a range of RPM changes.

 

But I don't see the OP mentioning "all gears" just that it occurred over a range of rpm.

Should be easy to check though, OP could see if it does it in 2nd gear or not.

 

Wow I didn't even think about the torque convertor lockup, that make more sense because it did it in while in OD at several different speeds/gears, but not in the low gears. Another reason I love this site, everyone has sooo much knowledge !!!!