The customer brought us a 67 Firebird that he swapped with the l94 and 6l80e out of a 2012 Escalade complaining about a "dead spot" in the throttle. After some initial inspecting, a combination of the Holley lo-ram intake manifold he installed and a shorted MAF signal circuit within the ECM has caused the fueling in certain areas to be really lean (>20:1 AFR), especially on throttle transitions. Because of the MAF signal circuit failure within the ECM, and the lack of availability of replacement ECMs, I'm trying to tune the car to just run in speed density. Also, the Holley intake manifold points the injector towards the center of the engine, rather than the top of the intake valve like the stock manifold would, which I suspect is causing a bunch of the fuel being injected to pool up in the intake runner and just dribble down into the cylinder once the valve opens. Despite having taken The Tuning School's course on GM gen 3 and gen 4 tuning and being pretty familiar with the tuning process, they don't cover anything about aftermarket intake manifold upgrades, transient fueling, or injector timing in the course, and this is the first aftermarket intake manifold that has given me any major problems. I've messed with the injection boundary table [13336], normal ECT [13337], impact factor gas [13624], impact factor gain [12284], evap factor gas [13627], and evap factor gain [13630] to little avail, in addition to trying to clean up my VVE table somewhat, and trying to account for the lean spots. I thought I was making some progress until I got to the point where I was flooding the engine on startup, despite not touching a single table directly related to cranking.
I really just need some pointing in the right direction, as I feel like I'm flying blind and adjusting things little by little randomly. Everything about the engine is stock except for the intake manifold and a set of long tube headers. DoD is disabled and cam timing is at 0.0 degrees until over 4000rpm, but all of my issue is in low rpm throttle tip in. I can watch on my wideband that any throttle delta sends the AFRs super lean, despite my injector duty cycle closely following my throttle position.
I've got the original tune that I pulled from the car, with just the MAF disabled, and then my latest tune that successfully made the car run, where my throttle response was a bit better, but floods the motor on startup (or possibly on shutoff, I can't say for sure). Because of the way the ignition switch is wired, I can't log cranking since the OBD2 port loses power in the run position of the key, so unfortunately I don't have that information.
Any help or advice would be greatly appreciated.
67firebird_62_6l80e_rev2.hpt
67firebird_62_6l80e_rev16_refresh.hpt
67firebird_62_6l80e_rev19.hpt
67firebird_62_6l80e_drive1.hpl
67firebird_62_6l80e_idleandrevs.hpl
67firebird_62_6l80e_idleandrevs11.hpl
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Originally Posted by edcmat-l1
