Bamato

iTrader: (6)

I think I've asked about this in the past. But it's been a while, and I thought the problem was fixed. But it's returned with a vengeance this time. Long story short, at anywhere from 2 lbs of vacuum to 5 lbs of boost, and UNDER 4200 rpm (but above 2000) my 7 will surge, sometimes violently enough to break the tires loose. If I stomp on the gas, it will accelerate fine. If I feather the crap out of it, its fine. Anywhere in between and I'm jerking back and forth rodeo style. It doesn't do it when the car is still cold, and it leans out every time it jerks. AFR's will jump up and down about a point or two each time it jerks.

I've replaced the TPS, multiple times, and it first it would seem to cure it. Now it has almost no effect on on the problem. And trust me when I say I know I'm setting the TPS correctly. I've even built a test pipe so I can idle the car during adjustment. 1V.

I've checked for vacuum leaks, thoroughly. No luck.

Primary injectors were recently cleaned.

-Some background info - 3" exhaust, 720 secondaries, walbro fuel pump, rtek 1.7.

POSSIBLE THEORIES:

At first, it seemed like the 3800 rpm hesitation thing (3600 for me since I'm rtek'd). So I was going to clean the engine grounds, but it started doing it all over the rpm range now. Should I still bother to clean the grounds? Which grounds? Just the one behind the intake?

Also, I thought about testing TPS voltage at the ECU. But I'm not sure which pin/wire to probe. Suggestions?

Not sure when the fuel filter was replaced last. Although you'd think when I stomped on it, it would damn near die rather than drive fine.

Could my stock FPR have anything to do with this?

AGreen

iTrader: (11)

Usually if a FPR fails, it's the diaphragm that ruptures, and causes the engine to run rich at idle, fine while romping. I'd check all your grounds, replace the fuel filter, check the coolant temp sensor, and check the AFM.

Bamato

iTrader: (6)

Thanks Agreen, that gives me stuff to start eliminating.. I'm assuming the FSM gives methods on checking the coolant sensor and AFM?