Engine revvs when braking. Any Ideas?

[Rabid Hobbit]

Hey I've got a 06 Explorer V6 (26k) and for the past 2 weeks my engine has been revving when braking. Not horrible but noticable about 1k rpm jump up. This seemed to start after my engine started knocking and stalled going up a large hill, after i cut the engine off and back on it never stalled or knocked again. I have no idea if these are related but figure it should be noted. Any ideas why it would rev like that? Thanks

 

[BrianDye]

Could your brake pedal somehow be pushing your gas pedal?
Wires caught or something....?

 

[Rabid Hobbit]

Not anything catching that I can see.

 

[fixxxer]

Check to make sure the carpet isn't bunched up and causing problems and check the throttle cable too.

 

[Rabid Hobbit]

Check to make sure the carpet isn't bunched up and causing problems and check the throttle cable too.

I didn't check to see if the carpet itself is putting pressure on it. I know there is no wires or floormats touching it but I can check that when I get home today. Also I heard a bad IAC could cause a dip in rpms but could it cause a rise in rpms?

 

[Rabid Hobbit]

Check to make sure the carpet isn't bunched up and causing problems and check the throttle cable too.

What am I supposed to look for on the throttle cable. You mean just rev it up by hand and see if it still does it.

 

[big5dogg]

maybe brake booster it runs off your engines vaccum problably faulty

 

[Rabid Hobbit]

maybe brake booster it runs off your engines vaccum problably faulty

Is a brake booster user replaceable or something that only a service tech should repair. Also is there some surefire way to check it. Thanks

 

[fixxxer]

Just check to make sure the cable isn't routed in such a way that pressing on the brake pedal doesn't cause the throttle cable to tighten up and cause the acceleration. Another thing to check would be a vacuum leak at the brake's vacuum booster. A sudden loss of vacuum when the brakes are used could cause a change in the air/fuel ratio.

 

[Rabid Hobbit]

Yeah I think yall are right about the brake booster. The brake pedal has seemed a little funny lately too like its pushing back towards me when I slow down. I'll check for a vacuum leak this weekend. Thank you fixxxer and big5dogg. You've been a big help.

 

[fixxxer]

You're welcome and good luck!

 

[dothedeww]

Just last night...wheenever I would get on teh gas hard...it would knock real bad. Then on my way home whenever I braked it would rev...I would have to hold on the brake at a stop light or it would take off. Dont know if this was just a coincidence or if im experiencing the same thing. I have an 06 XLT with 76k.

 

[fixxxer]

Besides the knocking, did you experience any other performance issues? You might also have a vacuum issue related to the brake booster, check for loose or missing vacuum hoses and listen for vacuum leaks in that area.

 

[dothedeww]

No real performance loss..I just checked for vacuum problems last week...couldnt find a single leak.

I did just install the KKM intake before the problems yesterday....I guess that could be affecting the engine?

 

[shaker1]

If you had a vacuum leak at the brake booster you would be running lean from unmetered air. Then after adding even more air with the intake it might get more noticeable.

 

[tbe2002]

Just to let you know there is no throttle cables on 03 and above explorers. It is all drive by wire. The pedal is just attached to the firewall with an electrical connector coming out of it.

 

[explorinitup]

when u hit the brake do u hear a hiss if the brake boster leaks it will cause a vacume leak only when u hit the brake. and can and most likley will cause the motor to rev

 

[Rabid Hobbit]

Well I got the problem fixed. I checked the brake booster and lines and they we're all fine. So reluctantly I took it to the shop and it turns out it was a computer error causing me to downshift early. That why my rpm's were spiking when I was braking. It was $175 to flash my cpu so not too bad. But thanks for all the responses.

 

[shaker1]

Good info. So few people post solutions, just questions. Cheers.

 

[rmurray]

I think I might have the same problem. Engine revs when stopped or braking. Increases about 1k RPM. Now, I've noticed that when I'm accelerating, it sounds like rushing air through the motor. The tranny seems to be less inclined to shift, but then it goes away. It could be a vacuum problem I guess. Seems odd that it comes and goes. Any ideas?