i have a s5 GXL and the idle lopes. ive replaced all the gaskets in the intake manifolds, the o ring on the TB, and all the vacuum lines, and tested with several methods for a vac leak, but none. i made sure everthing on the TB moves freely and is correct, according to the FSM. i adjusted the tps, a little better but it still lopes. my fuel pressure at idle bounces about 5 psi, if i remeber right around about 45psi. but could the fuel pump resistor relay being bad cause this problem? ive also heard it could be the MAF. has anyone else expirienced this problem or have any ideas on it?

 

Have you tried to bypass the fuel pump relay resistor?

 

reset the idle per the FSM, ground the terminal near the check connector and lower the idle speed screw setting.

set the TPS to read 1 volt at idle off the green wire from the TPS with the engine warm, key on engine off.

the simple reason these engine lope in idle is because the idle is simply set too high and the ECU is retarding the timing to try and force it down.

 

do you mean hooking up the fuel pressure guage, letting the car idle, and disconnecting the fuel pump relay? and see if i get a improvement.

by the way if i drive ~20 mins to work or somthing, the idle will lope ~40% of the time and the rest its fine. but the idle is never in one spot, somtimes its1900 somtimes its 1100 and ect.

 

I'm talking about disconnecting the plug to it and installing a jumper wire in the plug which removes the relay from the fuel system.

 

well, 45 psi is too high anyways, if that was from an accurate test. but the idle needs to be at or below 1000 RPMs otherwise the ECU will try to force it down with the idiotic "loping" procedure that it does, which really does nothing at all except make the car sound like it's on crack.

 

i will try bypassing the fuel pump relay. but which wires should i jumper? the connector to the resistor/relay has six wires, 2 for the resistor and 4 for the relay.
and karac, maybe i made a little mistake, so i will redo the idle on the TB, since the idle screw wont lower it enough and see if that helps.
and i dont think this would affect idle at all, but my leading coil is done, judjing from several different test, so its not even in the car at the moment but the ECU doesnt throw a code for it??

 

The car needs the leading coil to operate properly so that should be top priority.

 

ya but there is no code for it? thats weird!

and it wouldnt affect idle, correct?

 

the car will have a severe lack of power with just the trailing coils firing, about 25% less power from my last dyno test results.

 

wow i was thinking like ~15% or so.

 

maybe it was closer to 20%, the last time i saw a car i was tuning it and ran into an issue with power output. the car was at around 200 and jumped up to 250 with the leading coil plugged in but then ran into fuel system issues.

 

anyone else have a input??

 

ive looked and looked but cant find how to do this on a fc.
do you know how?

 

If you unplug the resistor/relay, and jump a L/R wire to a L/G wire (harness-side), you'll bypass it. Just be sure not to connect power to the G/R wire; that goes to the ECU.

 

i adjusted the TB so the primary throttle vale is a little more closed (to make sure the idle cant be above 1000)
and bypassed the fuel pump resistor/relay, but neither hellped the idle lope.

 

anybody know what else will cause the idle to lope and be erratic?
please

 

what is the order of the colored plugs to the solenoids on the rats nest? (maybe one got switched around when i replaced vaccum lines.