Hello I have a s5 turbo rotary with a bouncing idle. I checked the tos because that the last thing I had messed with. The multi meter says that it is within the FSM range. So I tried driving the car and the breaks started to loose power from the booster and my vacuum was reading 0-5 so I figured ok it's a big vacuum leak. I replaced all the intake gaskets and checked the intercooler it was leaking. Started the car up still bad vacuum. I tried the propane to find the leak and found nothing so I tried starter fluid next and no leak can be found though when I spray starter fluid into the motor the idle does change. I also checked my compression and that seems good. Has anyone heard of or dealt with this? Is there anything inside the motor that could be causing a big vac leak. My water jacket and compression seem to be fine

 

There's a vacuum hose at the brake booster which can cause a leak. The injectors can leak around the rubber seals.

 

Thank you. I will try the injectors next. I've removed the break booster vac line and plugged it and the problem is still there

 

I just replaced all the injector seals. Still same problem. Jumps to 3 - 5k on start up then pulses 1-2k.

 

emissions still there? FMIC or stock top mount?

 

Stock top mount. All vac lines from under the intake manifold and emissions have been removed

 

Have you actually tried to set the TPS? Green/Red wire set to 1 volt w/key to on after the car has been driven for at least 20 minutes.

 

Yes. I've set the tps with the multimeter like the FSM says to.

 

The FSM mentions the method via two LED lights. I'm not talking about that.

And does the bouncing idle occur all the time or only when the engine is cold?

 

I didn't do the led test because I don't know where the test plug is located. Just under the test light section in the FSM they have a ohms check for low and high throttle open and closed and that's what I tested the tps is in the ranges they gave in the book.

Idle pulse is all time at any rpm I can hold the throttle steady at a higher rpm and it'll still pulse.

 

You might want to try the voltage method as previously noted. You could also have a chipped apex seal as I think that would create a pulsing idle as well. And what happens if you unplug the TPS? Does it pulse when in gear as well as in neutral?

S4 or S5?

 

It is a s5 motor. Would the chipped apex seal still show good compression numbers?

 

If I unplugged the tps it throttles at like 6 or 7. If I try to drive it the idle still pulses. The car starts jumping forward

 

Hundred or thousand?

 

Thousand.

 

Did this occur w/the engine cold or hot?

 

Both I believe. I will double check later today. I don't let it run very long with the tps unplugged because it's high rpm and loud, neighbors tend to not like it.

 

The engine normally idles above 3000 rpm when cold briefly thus the TPS being disconnected could exacerbate that speed because when the TPS is unplugged the ECU defaults to a full throttle setting. So see how it idles w/the sensor unplugged not when cold but fully warmed up. Take notice of the rpm and whether the idle bounces or not.

 

With car warm and tps unplugged the car sits at 6k rpm doesn't drop and does seem to pulse I only kept the car on about 30 seconds. With tps plugged in it pulses 1500 to 2k and my vacuum gauge reads 0 to 2.5 inHg

 

Not sure what to say but when unplugged the engine should not rev at such a rate. If I were to unplug my TPS while idling it stays at basically the same level. I'll defer to others to chime in w/their insight.

 

Smoke tested the pig? Vacuum leaks can be a pain. I have a video in my build thread that shows a paint can and some 3/8"th air compressor fittings modified to accept smoke bombs to see if you have a leak.

There are other various backyard smoke machine methods, but this worked for me and cost under $10.

 

I just smoke tested the motor and the smoke is going out the exhaust port and threw the turbo. So the turbo seals are so bad it lets air threw from the exhaust back into the intake side