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Problems idling with "mild" camshaft.

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  • Problems idling with "mild" camshaft.

    Backstory. I'm doing an LSx swap into a 1991 Firebird. Before the swap, I wanted to make sure I have most everything up & running and bugs ironed out before doing the swap into the car. So I build an engine run stand, which has already saved my butt on a few little issues that were way easier to fix on the stand versus having the engine in the car. I have a fuel system, radiator, and a control stand for the Terminator X and 3.5" TSLCD and switches and relays, etc. I'm also using a laptop with the CAN Bus cable when needed.

    I can get the engine to run on the base LSx tune with some parameters changed for my engine. It's a 421 cid LS3 stroker, 58x crank, with Frankenstein LS3 ported 823 casting heads and a BTR Stage 3 400+ci N/A cam (0.631"/0.610" lift, 239°/254° @ 0.050" duration, 114° LSA. Kind of a bigger cam, but only a tad bit of overlap IMO) and a FAST LSXR 103mm intake and DBC throttle body.

    The engine runs pretty damn good if I keep the throttle cracked and keep it above 1500 RPM. But as soon as I let go of the throttle it surges a few times and dies. I've adjusted the throttle stop and recalibrated the TPS sensor a few times and I can get it to idle at like 1750 RPM, but can't manage anything much lower than that. I also see AFRs in the 25-30:1 range at 2000 RPM on my AFR, but I'm almost positive it's because in between exhaust pulses, raw air is coming back to the WBO2 sensor since I just have the Holley BlackHeart Headers and no collector extensions (which I just put some on, but haven't checked it yet to see if that changed anything). The plugs look rich if anything and not anything indicating that lean (it shouldn't really run at all that lean). That's lean misfire territory.

    Some videos for reference are on my car's IG page. Here's a link to the post you can see a few videos.

  • #2
    If you don't have at least two feet past the WBO2 sensor, the ECU will start adding A LOT of fuel once the engine drops below 1500-1700 RPM. If I can be of service with the tuning, please email me: projectgattago at gmail dot com. Andrew
    Instagram: @projectgattago
    Offering remote Holley EFI tuning.
    I deliver what EFI promises.
    Please get in touch if I can be of service.


    • #3
      Originally posted by Gunmetal421 View Post
      ...BTR Stage 3 400+ci N/A cam (0.631"/0.610" lift, 239°/254° @ 0.050" duration, 114° LSA. Kind of a bigger cam, but only a tad bit of overlap IMO) and a FAST LSXR 103mm intake and DBC throttle body. (Read 2nd paragraph under "Wideband O2 Sensor Notes".)
      May God's grace bless you in the Lord Jesus Christ.
      '92 Ford Mustang GT: 385"/6.3L SBF, Dart SHP 8.2 block, forged steel crankshaft & H-beam rods, forged pistons, Trick Flow Twisted Wedge 11R 205 CNC Comp Ported heads, 12:1 compression ratio, 232°-244° duration/.623" lift/114° LSA camshaft, TFS R-Series FTI Comp Ported intake, BBK 80mm throttle body, Holley Dominator MPFI & DIS, Holley 36-1 crank trigger, MSD 1x cam sync, PA PMGR starter, PA 200A 3G alternator, Optima 34/78 Red battery, 100HP progressive dry direct-port NOS, R134a A/C, Spal Dual 12" HP 3168 CFM fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, Earl's -6AN fuel system plumbing, Walbro 255 LPH in-tank pump & Pro-M -6AN hanger, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio Ford AOD, 10" 3000 RPM C6 billet converter, B&M Hammer shifter, Stifflers transmission crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.


      • #4
        I use a 6" piece of pipe on one header for my engine run stand. The wideband oxygen sensor is 4" past the collector, then the 6" piece of pipe. It makes a world of difference.


        • #5
          Disable WBO2 in settings and manually tune fuel map in problem RPM range.


          • #6
            That's what I ended up doing just to get some run time on the engine. You'll have a pretty wide range of fueling at idle that you can't tell the difference. Once I found an extension and got it on, the AFR was in the mid 15s, so I adjusted it from low 12s to high 15s and very little difference, but it was a small cam 5.3L.