Engine revs when brake is pushed
 

Just had my RE motor rebuilt and put in. It has a single turbo TO4E with an RX-7 store fuel sytem, 850 primaries and 1600 secondaries. The motor idles like it is breathing, up-down, up-down and when the brake is pushed it revs the engine. Now the gas pedal also revs the engine so they are not swithed somehow. Any ideas?

so... when u push the brake, you get a throttle like response, or when u push the brake u get somewhat of a higher idle? cuz if you get throttle response from the brake... someone somewhere put some work on fuckin ur car up

if it only raises ur idle slightly, you could have somewhat of an electrical issue
such as when my car is idling and i turn the running lights on it will make the RPMs fluctuate for a second, it will jump to 1100 rpms and then normal out

Maybe a vacuum leak in the brake booster?

almost certainly a vacuum leak, it may not just be confined to the brake booster as a vacuum leak anywhere will cause the problem. start hunting down vacuum leaks my friend, you have a big task at hand. i'm about to start a vacuum leak hunt myself. gonna be a pain in the ass.

you may as well replace your hoses with either oem, silicone or viton ones as well, and make sure to have the little replacement nipples you can buy from dale for 15$ a set. also if you're removing hoses, cut the old ones off by slicing the ends first, don't pull them off or you'll break solenoids and all kinds of other stuff in the process.

Have someone watch the TB will you press the brake. If the brake doesn't move the throttle cable, go from there.

^^LOL

I'm assuming we're talking about a manual transmission?

Try taking off the vacuum hose going to the brake booster, and plugging it with your finger. Then have someone else step on the brake and see if the problem still occurs (super unlikely to still happen). That would narrow it down the brake booster being your vacuum leak.

lol at merlins pic.


Anywho, this sounds like a vacuum leak, but if it is just a very low surge in idle when the brake is pressed that sounds like a ground/electrical issue. How high is it reving up? Is it 100 rpms or 1000?

It revs very high, like 3000 to 4000 so I guess it is a vacuum leak somewhere. How do you narrow down where it is besides the hose on the brake booster? Would a leak down test show a leak or not?
Thanks for all the help!! ;)

My FD idles a little higher aswell when I turn the lights on.It jumps to bout 1100rpms and then gradually normals out to bout 900 if that is normal????Was doing my nut in but I recently bought an earthing kit which I am waiting on and gonna throw that in to see if it makes a difference

propane without the flame... it can be your friend in this vacum leak hunt

I think you should look at the brake booster check valve before getting too concerned with other sources of vacuum leak.

Perhaps there a chance that this happens when you wear bigger shoes?

Sorry, start with the easy stuff.....

The brake pedal sits much higher than the accelerator by design. You'd only accidentally bump the gas if you were pushing the brake hard or something is caught between them.

Dave

Or if there is a LOT of movement in the pedal...

Seriously, Crit has a good point.

Dave

This could possibly be right, but I doubt it. I am leaning more towards vacuum or electrical/grounding issue.


http://raimo.com/images/719_find_x.jpg


hahha j/j,
-josh

Im having a similar problem... thought my car had a vac leak for a while.. when i pump the brake at a stop the revs jump about 150ish.. is this normal?

Agreed, I believe it sits in the hose that comes off the brake booster and runs to the hardline on the firewall.

-Dan