Hi guys,

No idea what's going on with my car. I feel like every other week I'm under the hood fixing something. Car was running great lately, then I did a first gear run under half thottle (not too hard nor boosting over 8psi) and then after that the idle won't drop below 1.5k. I just bounces up and down from like 1.5k to 2.5k as if there is a vacuum leak. The boost gage shows bounding up and down from like 20-15mmhg which also indicated a vacuum leak. I check all the vacuum hoses and they all look great. All vacuum hoses were replaced per the Dale Clark instruction about 1-2 months ago. I just hoped I didn't crack a seal or something...

I let the car sit for a while and then fired it back up and the idle went up to 4k till i blipped the throttle and then it dropped down to 2k and bounced around from there. I can't go under the hood to listen for a vacuum leak cause it's so loud under there at that rpm.

Any idea or common things that could cause this?

Mods:
mid pipe
downpipe
racing beat exhaust
stock twins and intake box
stock everything else

Thanks for any help or pointing me in the right direction!

 

check your TPS voltages to make sure they're within tolerance at idle

 

Ok I'll check out the TPS. I don't know why all of a sudden it would act up like that. It was golden before that.

If you got any more ideas for me to check, I'd love to hear them.

Thanks!

 

I would also check ISC and AWS to make sure they are not sticking open. I have a unlit propane torch with the end cut off and vacuum hose attached to check for vacuum leaks. Works great and isn't messy like spraying carb cleaner.

Check TB linkages and cruise control cable for butterfiles being held up.

For the idle to be that high the car has to be taking in additional air from somewhere.

 

Agreed. It's reving pretty high, even for a small vacuum leak. I'll check the ISC and AWS like you said. I'll dig into this thing over the weekend and hopefully figure it out.

Thanks man

 

My new method for finding vacuum leaks is a smoker/fogger.

Something like this: http://www.proaudiostar.com/chauvet-...A0uxoCYJnw_wcB

Duct tape a silicone hose to the smoker, pop off the brake booster line and push smoke into the manifold. Most leaks will seep under that small pressure. Others show up when i blow throw the booster hose after filling the manifold with smoke. It works awesome without spraying messy carb cleaner or risking a fireball in my hand. I'm a little nervous about the open propane torch in a running engine bay.

 

I had always heard that those type machines were expensive but that one isn't.

I do use a long length of hose so I don't have to hold the propane cylinder right down near the engine. I got the propane method from some old Honda FSMs that specified the use of propane to check carb mixture. There is some risk to everything. The risk of it becoming a "fireball in your hand" is quite low.

 

This works well but I have never scrutinized it from a safety standpoint if something was to ignite the gas. Also, I have heard that propane is heavy and can settle in areas.

I know the use of propane for vac leak checking is talked about in other car forums but not necessarily via hacking off the end of a torch. It could be advisable to use a different setup. I don't have much experience with this kind of stuff so I just don't know.

Something made me think again of this recently and I realized I had posted about it several times.

 

Before you do anything spray brake cleaner around and under the intake manifold with the car running. If the idle drops, you are in the vicinity of the leak.

TPS can move and go out of spec if the set screws come loose.

ISC can stick. Pretty common. Unplug it with the car running and see what it does.

Check to make sure the throttle cable and cruise control are not sticking.

The throttle body can stick mechanically.

The dashpot can stick.

 

Thanks guys. I actually went to the dark side and pulled the Rotary and am doing a LS1 swap now. I need the reliably for the track and street. Love the car and will always treat her well but she needed a heart transplant.

Thanks again

 

Lol a rotary can be reliable, but honestly its a lot less forgiving. Do what makes you happy with the car.

 

Thanks man. I have mixed feelings for doing the swap but I kinda feel like I'm getting the best of both worlds. We'll see how it goes. New heads are going on the engine now. I'll always be a Rotary fan too. It's all love.