Let's see... first of all, the car stalls at idle.
Cranking the engine doesn't start the car too well unless you tap the gas while cranking it...and if you don't hold the gas it'll fire, rev up to about 2200, and die.
Once it's warm it's usually fine...but the stalling usually happens when approaching a stoplight--pressing in the clutch while braking makes the engine rpms drop to 0, or in some cases drop to about 500, pick up to 1000, and then die.
At idle there is a constant put-put of minor backfires in the exhaust. and revving it up sounds nice, but letting off results in a loud crack.

Hooker long-tubes, O/R X pipe, Magnaflow straight-through mufflers.
Pulstar pulse plugs.
BBK 78mm Throttle Body/Upper plenum, K&N cold air intake (passenger side bumper area).
Oh, and the ECU is a Steeda unit, programmed for a vortech supercharger with about 7psi... Possibly the tune on the ECU is the source of all my problems.

 

The tune is probably the cause, yes.

Firstly, Vortech/Steeda sends out very conservative tunes so they don't blow up their customer's cars. This is good for liability reasons, but terrible for the end user. You are most likely going to have to get yourself a better tune somehow.

One of the biggest problems is that Vortech puts the IAC before the blower. This is really, really bad because you don't know how hot the air actually is going into your engine. Thus, they have to retard the ignition fiercely so you don't get detonation. However, that means that your engine never really knows how hot the air going into it is, which means all of your tuning is based on the guess of someone who has never even seen your car before. Not good.

I would guess that your timing is so retarded that your car can't start itself reliably. Once the blower heats the air up, the timing is back on track which is why it runs well when warm. Giving it some gas changes the position on the timing map, presumably to a cell that is good enough to start the engine.

Now, when you press the clutch in and the RPMs fall and even stall, this is probably caused by a combination of poor timing control, dashpot functionality, and fuel mixture.

We already went over timing. Basically, if the timing is retarded too far when you clutch in, the engine can't get a good ignition and loses power and RPMs.

The dashpot controls how much air is let into the intake when the throttle is closed, and how much air to bleed off when the car is coasting. If the settings are wrong, then there is either too littler air to keep it going (so it stalls), or the RPMs fall so fast that the car can't catch itself in time (which is where it can stall or stop at 300 RPMs). When you add a blower, you add a lot of parasitic drag to the engine. This drag needs to be compensated for in the dashpot.

Finally, the mixture. You really need a wideband O2 gauge to monitor this, as this is one of the most important parts of a supercharged car. Since Vortech/Steeda makes the mixtures rich, the car may be flooding itself when you press the clutch in. This causes it to lose power and RPMs. A wideband gauge will be able to tell you if you're rich or lean when the car stalls, which will tell you what part you need to look at.

I would bet that the tune is certainly causing a lot of problems. At the very least, hook up a datalogger and see what your fuel trims are doing. At idle, your backfire is probably being caused by a combination of timing issues and mixture issues. A datalogger and a wideband will be able to tell you with much greater clarity where the problem is and what to do about it.

 

Wow, that is one of the most informative replies I've ever seen.
Thanks a lot.

(My wife was logged in when I made the original post)

Anyway, the car isn't supercharged right now--it's running N/A since I sold the blower and my Diablosport...
But the guy hasn't paid up and it's been awhile, so I'll be reverting to the supercharger. Lucky I never took off the supercharged badges.

Anyway I work at a car dealership now, so I'll see if they can hook me up with a new PCM or at least a reflash.

I just changed the air filter (a K&N but ridiculously deformed and dirty) for a new wider K&N...and the problem with stalling seems to have gone away. Too bad it seems I'm leaking coolant and oil slowly.

 

No problem! I'm also glad it seems to only have been the air filter, as tuning out some of those problems can be a nightmare.

A big problem could have been running the blower tune without a blower. Again, those tunes retard timing immensely, as well as change the fueling tables up top. They also have to adapt the airflow readings, temperature readings, load calculations, etc, to compensate for the extra air. If your engine was expecting a blower and wasn't getting one, then everything would be screwy.

I would be surprised if reflashing to stock didn't fix many of your problems. However, be advised that if you made any supporting mods for the Vortech (like a MAF upgrade, injector upgrade, etc) and try to use a stock PCM file, it won't run well at all. Heck, it might not even start. If you added parts for your supercharger, your PCM needs to be modified to accept the new parts.

I guess what I'm trying to say is that you'll need different tunes for if you have the blower or if you don't. If you delete the blower, you need an NA tune. If you put a blower on, you need a blower tune. Without updating the tune, the engine will run poorly, as you've experienced.

Good luck!

 

Thanks alot.

The stalling came back, my heater core blew, and all sorts of fun has been had.

Anyway, I'll try to reflash and then play around with my Diablosport to try to make things work out...
Hopefully, being a car salesman will cut some of the cost out of the service appointment.

 

Ouch. Yeah I read about your other thread where the smoke leaked into the cabin and made you and your wife feel sick. Certainly not good, lol.

The first thing you need to do is decide what tune you need. Since you're taking the blower off, you will obviously want to get a tune that isn't based around a supercharger. However, like I said before, if you've changed injectors or MAF since stock, you absolutely do not want to use a stock tune. At best your car will run terribly, and at worst you could damage something.

Can you give me a list of mods for your car? If you do then I can tell you if the stock tune will work or not.

Also, you said you have a diablosport something-or-other. Is it a full-fledged tuner (with an LCD screen and buttons such) or just a chip? If it's a tuner then you don't even need to go to the dealership, because those tuners save the stock tune in their memory. To get back to stock, all you should have to do is re-upload the stock tune. It shouldn't take more than 5 minutes.

Once you get that taken care of, we can make all the tuning changes and upload the new tune directly to your car. I'll be glad to help you through the process, although it's pretty straightforward. For the most part you'll just be entering info about your car, and the tuner will generate a tune for you.