Fuel stroker help

junkyardwarrior

Active Member
Jan 10, 2011
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92 GT, swapped to a stock block 427" windsor (4.170 stroke 4.03 bore). Super victor EFI (29245), 80 lb siemens injectors (new). A9P, using A9L2 tune via quarterhorse. AFR205. Hooker long tube headers full 3" header to bumper, H in the middle behind the transmisison. Stock 5.0 harnesses. 3G 130. Ed cam 250 at 050 and roughly 600 lift. Hyd roller.

I am fighting this thing and getting upset with it. Runs fine at full throttle, idles ok-given the cam profile. Cruise is decent although it is rougher than I think it outta be with sefi. Here's the issue. With the laptop hooked up (tunerpro rt) I am watching FUELING. Idles at 165 imaf. Two things...one, as SOON as I hit the throttle, even slowly, it goes LEAN for a second or two, and returns to a sane a/f (idles at .92 Lambda, will peg the AEM WD at 1.25+ for a second or two, and can feel the engine lose power in that time). If I stab it, I can watch the WB go rich for a split second and it runs fine. If I very very slightly move the throttle pedal from idle (165 imaf) to, say 175 imaf, it will go lean for a second. Lambses will dump fuel for a second or two and then return to 1.0x which is where I want it. Lambse mostly follows the WB.

Second issue....which might be related to #1. On a VERY light cruise speed, MPH doesn't matter nor does load....I can do it in neutral too....the RIGHT side of the engine (bank1) will go lean, Lambse will show 1.22 and sometimes more but only on the right bank (cyl 1-4). Left bank remains at 1.02-ish when I see this. IMAF shows under 200. Very low throttle input only. Soon as I start to throttle up a little, lambse1 will return to close to 1.00 (where I want it) and it will run somewhat better. At cruise, say 55mph although mph doesn't really make a difference--it's just right off of idle--I can feel the shifter "moving" as if the engine has a miss.

My thought? Vacuum leak....I have a smoke machine and I see no leaks anywhere. Had a couple when I put the engine in and fixed those. Did compression test, all 8 test 175-180 cold, and hot 180-185. Leakdown test cold about 7%, hot less than 5%--so I don't see any problem with the engine based on that. Tried swapping HEGO's nothing changes. Tried reassigning the HEGO's in the tune (e.g. "moving" bank1 to the left side of the engine and bank2 to right side) and nothing changed other than it really confuses the eec when it tries to correct the wrong side of the engine. Checked all grounds and seeing a voltage drop of less than 400mv on all grounds. Plugs replaced several times. Plug wires 3 times, I did initially have one bad wire which was obvious--but replaced several times since. Dist is a new 351w truck distributor from the parts store, and I swapped a motorcraft TFI module onto it just for giggles--no change. Sent ECU out for check-they found nothing wrong but put new caps in it anyway since that's common failure point. No change.

I think if I can fix this right bank lean issue it may solve issue #1 too but which direction to go? I'm tired of throwing parts at it. I've done all I know to do to eliminate possibilities other than replacing harnesses. Tried injectors too. Swapped #1-4 to the left bank and #5-8 to the right bank and that didn't change anything at all other than make me work.

You guys got any ideas that I can try?
 
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nickyb

WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
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nevada
When you did smoke test did you slightly open throttle? Maybe,just maybe vacuum leak? I mean you did check out all possible reasons.
 

junkyardwarrior

Active Member
Jan 10, 2011
349
87
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When you did smoke test did you slightly open throttle? Maybe,just maybe vacuum leak? I mean you did check out all possible reasons.
Yes. Tried all throttle positions. Just did 3 different tests. One, smoke test (clear). Two, intake pressure test (soapy water, about 10 psi in the manifold/throttle body). Flying colors....nothing under the dash either (checked and triple checked). Three vacuum test, used my electric vacuum pump on the intake and listened for leaks-none. Used a stethoscope to listen around everything that has a hose or line and even around all 8 injectors, as well as along the top of the intake manifold where it meets the cylinder head. Nothing. I mean it's sealed up pretty good. Even turned the A/C and heat control to all positions listening and watching-nothing. No leak at the speed control, not at the vacuum reservoir, and not at the booster (listened/looked under the dash). I had an inline ball valve rigged to the vacuum pump and turned the valve off, then the pump-and listened for leaks. It holds over 10"/hg for about 3 min, or a little longer. I had it at max 25"/hg and it will slowly drop off after about 3 minutes or so. I'm satisfied that it's sealed up good.

Then smoke tested the maf tube, removed the sensor and put a cap on the end of the tube in the fender well. All fine--zero leaks in any of that tubing not even at the fresh air tube connection or the filler tube (valve cover). So at this point I'm ruling out a vacuum leak or air leak between the maf and throttle body.
 
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