Alright guys, here i am again, this time with a different car.
So, the car is a 1991 Convertible, manual, completely stock! Nothing has been touched on this beauty, except the full racing beat exhaust we put on her last night. She ran perfectly fine previously!

Replaced the exhaust, Header back, and threw on a new stock S5 header as well, because of a snapped stud on the original. Anyways, had to remove the 5th and 6th port actuators to get to the block studs to remove the manifold. Disconnected the rubber intake snorkel, O2 sensor, and attempted to remove the starter as well, so the leading plugs were disconnected (To get to the upper start bolt) as well as the battery, these were plugged back into their respective place as well (I've had them marked).

And now, she will start just fine, but instantly dies if your foot isn't on the throttle. Now, I can keep her alive over 2k, with my foot on the pedal, She sounds way better now! She just won't idle...

So I need some help where I went wrong, or what this could be. I'm guessing something was accidentally bumped or such. I did look at everything for about two hours, unplugging things and testing the car, and plugging things back in.

Things I disconnected and reconnected.
-Exhaust manifold
-O2 sensor
-Lower Actuators
-Leading spark wires
-Split air pipe was disconnected and remains disconnected

 

Tps?

 

Sounds like a vacuum leak.

 

When you put the rubber intake snorkel back, did you reconnect the two air hoses (BAC & AWS) on the bottom?

 

I did reconnect the two air hoses, I think what I'll do is zip tie those, and the two actuator vacuum lines as well, just to make sure. I'll then try and do a vacuum leak test afterwards if she still doesn't idle. The problem is that she is at my friend's house, and not readily available to tinkering. The TPS is another culprit I suspect, but she wasn't touched at all previously. I know sometimes a vacuum leak can cause a 'high idle', I'm curious as to what lines could cause a 'no idle' condition.

 

I would make sure your MAF plug didn't work loose while you working on other areas.
That and vacuum leaks. Any time you remove those actuators and any vacuum lines something always manages to not seal like it did before.

I wouldn't mess with the TPS until you rule out everything else. I've never had a TPS make a car not idle at all unless it was completely fubar.

Do you have any check engine lights at all? Sometimes, like I mentioned with the MAF, it is easy to knock something loose and not notice. The connectors are getting old, haha.

 

Check your snorkel for cracks. After sitting for a while they can easily crack with the slightest bending, then when you hit the throttle the increased suction causes the crack to close temporarily.

 

It sounds like a vacuum leak. Try reconnecting the split air. Also, on the firewall side of the intake is the waterthermo something or other. It's plastic and brittle. It has a vacuum line that runs under the snorkel. Make sure the plastic thing isn't broken and the lines are connected.

 

So, I took off the entire intake, and of course I found a broken vacuum line. The line was actually underneath the Upper intake. Also, the fifth and sixth port actuators were frozen shut, so I replaced that with a nicely working lower intake. Oh, and one of the OMP/MOP lines snapped... I have a spare S5 OMP that i will probably have to find now.

Hopefully that line was the root cause of this. Never expected a simple exhaust swap would turn into a nightmare!

 

Car idles better than ever now! That vacuum line was definitely the problem, it was completely severed, replaced all lines while I was at it, Thanks guys!

 

Good for you.