Bad Idle When Pushing Brake

[trbohatch]

I have just noticed that my car will idle bad.....up..... down.... only when i push the brake!!!!! Have no idea what it would be HELP! It is getting really annoying.. And please explain in lamin terms!
Thanks

[Evo_Spec]

now i have no idea what i'm talking about, but if i were to guess it may be a bad battery, or alternator, just a guess

[Ryan]

Could be multiple things. intake leak, bad gas, clogged fuel system, poor electrical system, bad plugs, bad grounds, disty on its way out, incorrectly set idle... I had two dead cyls because of burnt valves...

Check easy stuff. Intake leak, grounds, pop off the disty cap and take a look, check for cracks and such. Maybe run a bottle of injector cleaner just for S&G, its nice to do anyway.

Try resetting the idle, I know mine isn't really happy unless its set around 1.5k. I think its just because of the weak motor, can't handle the normal electrical loads at that speed. I could nearly stall it if I had the fan going full bore, lights on, and brake.

Good luck... hopefully the answer is easy.

[trbohatch]

How do you reset you idle? I dont think that it is anything of the major ones that you listed. Car runs very smooth, and strong other than the idleing thing. also do you think that it might be the tps? i think that is what it is called? if you how do you set it correctly?

[hgallegos915]

It seems that the check valve that in the break booster went bad.

[trbohatch]

how do you fix that? in lamin term please...

[magiccowinuse]

My MX is doing the same exact thing, so any help for him will be help for me!

My roomate is a mechanic and he seems to think that it is a vacuum leak...but he didn't look at anything just saw the needle jumping when in my car.

Thanks for the help

[Nd4SpdSe]

PCV Valve.

If there's no check valve in the, the brakes still work fine, but the pedal drops when you turn off the car (Deimos didn't have one). I put in the check valve backwards, cause I didn't know it existed, and the brakes just don't work and the pedal goes rock hard.

[Ryan]

Pump the brakes 10 times to the floor when the car is off. You shouldn't be able to do it.

[Nd4SpdSe]

You should be lucky to get like 3 good ones

[trbohatch]

Ya my brakes work fine, it is just when i am stopped and push the brakes in then the needle starts to jump. I have a 94, and not really sure about the location of the check valve. I think that I seen something like it about one foot to the to the left of the brake booster but not really sure. and how would i change it?

[Mi|<E]

I found with my 94 B6 that the idle would go from 800-1200 when stopped almost like
an air hose is being pinched off then opening constantly.

Chasing parts didn't seem to solve it, the best advice I can give is to either play with
the timing/idle till you get it just right. Or you can unplug the Idle Air Control at the
rear bottom of the throttle body and adjust the idle manually at operating temp (make
sure the fan isnt on and you jump 10 and GND in the diagnostics box, use paperclip)
(Do not start car with diagnostics box grounded. Insert paperclip after car is started and
remove it prior to shutting the car off).

If you want to check error codes, insert the paperclip and turn the key to the on position
so the interior gets power but the starter does not crank. It will flash long 10's short 1's
and you can check components and see if all is well there while you are at it. Search
for more info on that, theres a really good write up by Shameem somewhere in the FAQ.

http://www.mx-3.com/phpBB3/viewtopic.php?f=24&t=65390 <-- that one

One other thing to try whilst messing with the idle/timing is to leave the headlights on
and try putting other loads on/off to get a good setting. I usually left headlights on and
the rear defog on aswell when setting idle to avoid it dipping too low.

Experiment.

[Nd4SpdSe]

I doubt it's the check valve that could give that type of symptome

What trbohatch describes tend to be common with a failed PCV valve onthe V6 and even happened to me, but can anyone confirm that for the 4cyl's? It's a cheap part, I would probably suggest to give that a try first.

[trbohatch]

can you let me know where the pvc valve is???

[cjthor]

can you let me know where the pvc valve is???

pcv valve is in the valve cover.