datz

so my s5 n/a is loping at idle. i havent found any vacuum leaks, sprayed carb fluid under the UIM nothing, changed BAC, AFM, TPS, TB, all gakets and ALL VACUUM HOSES do do with intake air, adjusted TPS and all adjustments to TB.
all acording to the FSM
but everyone keeps saying vacuum leak (but theres none)
when i turn the A/C on it stops loping
when i start it it idles fine with the warm up sequence (3k for 17 seconds then drops onto the fast idle cam) but once it drops off the fast idle cam it lopes at idle.
can anyone suggest anything other than a vacuum leak (cause there is no vac leak)???????

datz

this thread has been viewed 50 times and no one has a idea? really?

slevenfs

Sounds like you might need to take a look at your fuel distribution system. It may be loping because its not getting enough fuel (instead of too much air which a vacuum leak would suggest).

The reason I think this is because the engine startup sequence results in a richer air-fuel mixture, the ECU does this to warm the engine up faster and to help start the engine when its cold. Once the engine is warmed up the ECU switches to a leaner more efficient mixture. Second, when you turn the A/C on the engine has to work harder because the A/C pulley is drawing power from the crank, therefore the ECU creates a richer mixture for more power.

Any of the following may be happening.

1) your fuel filter is clogged
2) your fuel lines have a leak somewhere
3) your fuel pump is giving up
4) your fuel pressure regulator is giving up or is set incorrectly
5) your fuel injectors are clogged
6) your fuel lines are clogged

My guess is that either your fuel pump is getting old, or your fuel injector heads are dirty and need cleaning.

datz

ya i was thinking somthing in fuel system

pretty sure the lines arnt clogged and havent found any leaks anywhere at all and did replace the fuel filter
when i put a fuel pressure guage in line and let the engine idle the pressure would fluctuate with the rpm fluctuation, so that means its either pump, pulsation dampner, or pressure regulator, right?

and also my fuel pump resistor relay doesnt work, its not even in the car, theres jumper wires to bypass it.