Weird Idle Problems, brake causing higher & lower rev?!?!, Need some brainiac help please!!! Options

[jhaletama]

Hi guys,

Just had the head rebuilt on my 3sfe 1997 ST202 celica.

After being put back together couple weird problems.

1. If the car is started and just left to idle no problems, when you push the brake down it lowers the revs and as soon as you release the revs go up?! air con is off.

2. Once the car is warm and you drive it when coming to a stop the car wants to stall and die. air con is off.

3. when you drive the car at cold runs like a dream. once warm the above problems start. air con is off.

4. Car Temp gauge always sits about half way has done since i bought the car but lift the bonnet and you can feel the engine heat! it runs pretty hot. is this normal?

now the only thing i changed which is not from this engine is that black air valve on the top left side of the intake manifold. i accidently snapped the plastic tip so just grabbed another from a toyota camry. don't know if this will have anything to do with it or not.

when head was built, new gaskets from block up, new spark plugs, filters, oil, anti freeze.

any help would be greatly appreciated!!! Thanks again.

[808celica]

sounds like symptoms what i had before my original distributor imploded

use a multimeter to check the terminals and primary and secondary coils

[Bitter]

unplug and cap the brake booster line, problem still exist?

[azian_advanced]

for 1 and 2 - check your alternator.. it could be that the alternator is having a hard time providing current to the brake lights in the lower rpms, while the other components needed to keep the car running (ignition) isn't getting enough juice dropping the rpms lower and cause the engine to 'struggle'.

3 - replace O2 sensor

[jhaletama]

sounds like symptoms what i had before my original distributor imploded

use a multimeter to check the terminals and primary and secondary coils

No distributor on this engine.

[jhaletama]

for 1 and 2 - check your alternator.. it could be that the alternator is having a hard time providing current to the brake lights in the lower rpms, while the other components needed to keep the car running (ignition) isn't getting enough juice dropping the rpms lower and cause the engine to 'struggle'.

3 - replace O2 sensor

Hmm, well the car is running on an iffy battery so could that be half my problem?? Also on the intake plenum top left if standing in front of engine there is a black valve with a vacuum feed on it, not sure what it is, i broke the tip of it so hose couldn't go on but i grabbed another one off of a toyota camry, would this have any effect ?

[jhaletama]

Hi guys, any more suggestions?

[jhaletama]

bump

[DGAF]

unplug and cap the brake booster line, problem still exist?

Exactly. It really sounds like a power brake booster problem. It may be leaking and loosing all you vaccum. Like Bitter said. Unplug the fat hose going to the booster and plug it. DO NOT DRIVE THE CAR.... Now press on the brake pedal and see if you problem still exist. if it doesn't then you have found your problem.

[jhaletama]

Hi Guys update, new battery cleaned iacv and took for a drive, it didn't stall on me when i come to a stop but still idles very low.

At low idle, the car sounds like its missing, up the revs slightly (like 100-200rpm - or even just turn ac on) no problems, no missing.

the problem still persists with when idling and you press the brake revs go up the faster you push the brake the revs will raise and sit at about 1100rpm... now also turning the steering wheel does the same thing but not as bad as the brakes.

when i pull the big hose off the brake booster it oil gonna go everywhere??? any tricks to this test?

please pplz any help greatly appreciated its driving me nuts!!!

[Bitter]

no, no oil.

repeatedly pumping the brakes can raise your idle, thats normal. but hitting them once and that raises the idle alot while they're held is not normal. the power steering should raise the idle, thats normal.

[jhaletama]

no, no oil.

repeatedly pumping the brakes can raise your idle, thats normal. but hitting them once and that raises the idle alot while they're held is not normal. the power steering should raise the idle, thats normal.

no oil?

[blu94gt]

no, no oil.

repeatedly pumping the brakes can raise your idle, thats normal. but hitting them once and that raises the idle alot while they're held is not normal. the power steering should raise the idle, thats normal.

no oil?

If you pull the vacuum line, there should be no oil (if there's oil, then your brake booster is bad).

The brake booster has a vacuum line running to it from the intake. Vacuum from the engine helps move the brake master cylinder: this is how your power brakes work.

Now what I think is wrong is that
1. your brake booster has a leak in it, causing your engine to lose vacuum, or
2. most likely the check valve in your brake booster line is broken, which allows the vacuum pressure to leak, causing your problems.