Hey guys I need some advice since I'm stuck, I have a 91 Camaro, that I converted from v6 to v8 (I have a post documenting it) a couple years ago, its unfortunately still running a stock tune due to real life getting in the way, such is the way of project cars, I've finally be able to get back to it, and I want to work on tuning it but I can' t seem to get it to run "normally" to be able to start.

To break it down I'll describe what its doing at different stages

Idle:

Cold Start runs rough, rich with fuel (know the issue, 30lb injectors, stock tune) smooths out as it warms up
Idling after driving it for a bit, like pulling into a drive through and putting it in park, idles really high (~1500-2000 rpm based on sound, tach is dead)
Warm start, idles a little higher than id like but otherwise fine, Eventually raises as it goes into closed loop

Driving
If I start moving it while its still cold, it will either die right as it is put into gear, if it doesn't, it runs rough till I get to speed and better as it warms up
Once it is warmed up it drives perfectly fine in town and on the highway, easily able to get to 70+ mph no issues
If I keep a light foot on the pedal engine is fine, if I push the pedal past ~60% travel, the engine will act like it has no fuel, constantly misfiring, stumbles, no power whatsoever to the point the car is essentially coasting, but once I back the pedal off below a certain point, it clears out immediately and drives like any normal car would, but does not do that in open loop while warming up or a warm start.


Does this sound like its just a tuning problem that will be ironed out once I start tuning it, or more?

I've ran out of ideas on what to check. Advice?

TLDR
High Idle when Warm/Closed Loop
Normal Idle when Warm/Open loop
Rough Idle cold Start smoothing out over time (fuel smell)
Little power open loop
Drives fine closed loop
Engine misfires/acts like no fuel/stumbles past 60% throttle in closed loop, clears up once the pedal is below a certain threshold
Engine has no issue with Pedal position in open loop

 

Need some more details on the engine setup.

TPI or TBI?
MAF or MAP (if TPI).
Heads? Cam? Manifold?

 

TPI/MAP
Vortec Heads,
HSR
Comp's XE268AH-10 (Part# 2-242-12)
224/230 Duration, .477/.480 lift with stock rockers, 110LSA

Sorry for the late reply, had to make a emergency trip out of state

 

I can't say for sure that 100% of your driveability issues are a result of the calibration vs your engine setup. Don't know what condition the ignition system is, fuel system, sensors, the engine itself, etc...

But I can say that if you're running the stock calibration of a MAP TPI on that setup, you're definitely going to have a host of driveability problems.

The other thing to note is that engine swaps are often fraught with residual gremlins from the swap. Something not getting hooked up right.... a missing or bad ground, a forgotten vacuum line, some sensor not connected, etc. If someone swaps in a bone stock TPI engine and it's running well on a stock tune, at least there's a baseline to say that the swap was good. Then when modifications are done, it's already known that the swap was good.

On yours, I'm assuming it got swapped in with the mods you described already on the engine? In which case, now there's the additional variables of engine mods plus the swap, so there's no baseline reference to compare to.

Two ways you can go here...

1.) Try to get it tuned yourself. You can repost in the DIY PROM section where there are lots of knowledgeable folks who can help guide you. You'd have to download Tunerpro or some other tuning software along with the hardware needed. With tunerpro, you can take running data and do the tuning.

2.) Get a mail order tune.

Either way, you need to be 100% certain that the swap was done correctly such that the only thing to iron out is retuning for the engine mods. If there are swap issues, you could be seriously chasing your tail.

Just to give you an indication of MAP TPI sensitivity to modifications... My engine is farily well modified too, but I have a good running baseline. Over the weekend, I installed some 1.6 roller rockers. All that did was give me a couple of more degrees duration on valve timing and a little more valve lift. I could see the non-trivial changes in the fuel trims while datalogging and had to retune for it. The open loop cold start fueling had to be adjusted as well.

Now if someone is "flying blind" and not looking at running data after a small modification like that, they'd probably say it feels pretty good and drive it like that without retuning. But, as I started to get the fuel trims back inline, I could feel the performance and driveability improve. So, modifying the engine without retuning can leave some performance on driveability on the table.

But again, if just some 1.6 rockers needed some retuning, you can imagine how much is needed on your engine vs the stock calibration.