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DailyDriven'88 DailyDriven'88 is offline
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Join Date: Aug 2008
Location: CA
Posts: 181
Inconsistent idle surge

The surge has a range from 800-1200 rpm. Perhaps this is a clue: I can get the surge to stop if I give it small amounts of revving, maybe to around 1500 rpm and then let off slowly. It will then have a solid idle at around 800+- 50, and the AFR is at 13.6 to 14.2. When it surges, obviously the AFR goes up and down. Also, the surge usually doesnt occur until fully warmed up. All fuel pressures spec out. If I try to adjust the CO screw and or the idle screw to tune to surge away, it will work, but its only temporary, as the surge resurfaces everytime!! The only thing I havent done is presurize the intake tract...I will be doing it as soon as i can find a proper size adapter (anyone got tips for that?). I keep thinking it must be a vacuum leak but Ive triple checked everything vacuum related and have come up emtpy handed. I also keep hearing about a rich condition causing a surge? Ive also tried playing with the timing at idle. Latest thing Ive done was remove the fuel head and its plunger for inspection, thinking it may be sticking, but all was good and it had no effect. Valves just adjusted and leak down performed (5-8% across the board).


Background: Decel valve was removed years ago and lines were capped. AAR still installed and functions correctly. About 6 months ago, injector blocks were changed along with their gaskets, recirc valve resealed, new plug wires/plugs/cap/rotor, diassembled dizzy and relubed all components, WUR rebuilt by Leask, all new O rings throughout, a few injectors replaced due to questionable spray pattern, all new vac lines, timing is spot on (26@4k rpm), new filters blah blah blah and the car ran rather great! The K27HFS that was installed at the time failed so the car was down for a bit. A stock 3LDZ was reinstalled and the surge was noticed immediately. Triple checked all connections and found nothing wrong. I suspected the compressor side of the turbo was leaking (due to oil seepage at the bottom of the compressor to center housing mating) so I didnt worry about it as the 3LDZ was temporary. I then installed a GT35R and the problem still exists.

On a positive note, the car kicks butt with the GT35 and with the .8 spring in the wastegate, I see 7.5-.8 bar on the Andial gauge. Ive only taken the car up to about 5k rpm and not 100% full throttle thus far. Here's a pic for the hell of it:

Last edited by DailyDriven'88; 10-19-2009 at 09:10 PM..
Old 10-19-2009, 09:02 PM
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