I just bought an s5 TII with a blown apex seal. The vehicle was running well before disassembly, aside from the apex seal causing a rough idle. Engine was disassembled to the block by someone else. I rebuilt the engine, put a new apex in the rear rotor, and reassembled everything. Used an FSM, new gaskets/seals, torqued to spec, etc.

Reinstalled into the car, and would not start with the accel pedal released, it also took a while to start. It cranked normally, but you could head it flood. Depress accel to WOT to clear engine and it would crank faster, then find the spot on the pedal where it fires. This would be between 25%-75% depending on how long it flooded. Finally got it to fire up and it would not idle, it wont rev up to 3000 like it's supposed to from the AWS. Kept starting and played with the throttle pedal, and the engine would accelerate through the whole rev range. Built boost at idle, which seems odd to me. Brought the idles back down would sit around 500-600 rpm, touch the throttle and it dies. Rechecked found turbo charge pipe broken causing a vacuum leak.

Replaced, rechecked, now it will only sit at 500-600 for about 10-15 seconds before it dies. Checked throttle, was out of adjustment, resistance good, adjusted to 1v, now most of the throttle range will kill the engine and it will not accelerate past around 3000 rpm. There is an area near the top of the pedal where the rpm will increase slowly, but any play higher or lower than that and the engine dies. Unplugged BAC valve while idling and it dies. Turned screw in BAC valve and no change. Apply 12v and ground to BAC valve, and it clicks. AWS valve same deal. Rechecked for vacuum leaks, none found. All hoses routed properly. Water valve looks like it's working properly. When you open the throttle the second throttle plates open slower.

It's getting good air, fuel, and spark, so what am I missing? It makes no difference if the engine is hot or cold. It still wont start with the pedal fully released. Floods on initial start, and wont idle. I haven't found anyone with similar symptoms yet on these forums, so maybe someone can point me in the right direction, or tell me what I'm missing.

Thanks.

 

Bump.

 

Make sure your AFM is plugged in and that there are no air leaks in the intake piping after the AFM. Un-metered air can cause this symptom. You may have to pressurize the intake piping in order to eliminate the possibility of a leak. You can also check for vacuum leaks using the starter fluid method. Search the forum for info on how some have done both of those.

Aside from that, it could be anything since you apparently have had the engine out and may have misconnected something when reinstalling the engine. Carefully go over your work to verify that everything is connected correctly. Good luck!

 

Thank you. I know it seems like a vacuum leak, because that's what is seems like to me too. But I've checked multiple times for a vacuum leak and there aren't any. Usually it's apretty big leak that causes the engine to die, so it would be easily spotted. There are no codes so everything that matters is plugged in. Also wouldn't an unplugged AFM not allow the full rev range? If it was a vacuum leak wouldn't the engine not flood itself whenever you try to start it?

What would allow the BAC valve to control the idle enough to kill the engine, butthe adjustment screw would not change the idle? It's just an air bleed right?

Anyone have any other suggestions before I just start randomly disconnecting sensors and stuff until it runs well?

 

In case anyone cares, the timing was way off.

 

Appreciate the feedback! That can be very helpful to those with similar symptoms.