So I got HPT delivered a couple days ago, and decided today to see if I could read my GM SC recalibration... I knew I would probably get the checksum error, and did. I was doing this right as I left work, and had already started my car when I just decided to try. So I'm sitting in the parking lot with the engine idling, when the read process got to "preparing VCM" the engine died like the IAC valve closed, not quite "key off" quick, but it was fast and didn't stumble/surge at all before it died. That was when I remembered the engine has to be off. I never remember stuff in the right order
. So I wait for the read to finish, get the checksum error, and put my laptop back in the carrying bag.
When I tried to start the engine, it would crank but wouldn't even try to start. I pressed the gas and tried again and it fired right up and died as soon as I took my foot off the gas. I started it again, and very slowly let the RPM down to 800, at which time it started idling on it's own, and after a couple seconds the IAC took over and raised the RPM to about 1100 and then dropped back down to 900. So at this point I figure it needs to relearn the idle (which I never had to do before when disconnecting the battery on any J body), so I start driving home. At first the engine was a bit sluggish with less than 15% throttle, but that went away after a couple miles. It died at the first stop sign. Fired right back up (with the TB open a bit) but there was traffic so I didn't try to get it to idle on it's own. At the next 4 stop signs I left in in gear until 800 RPM and it died as soon as I pressed the clutch pedal. When I got home (15 miles) I started it back up, got it idling and then revved it up and let off the gas, and it died.
I have a "ScanGauge2" in my car. While I was driving on the highway, it read 50% engine load, which is right where it usually is with the absolute PSI (can't change measurements) at 7 or so. At higher throttle the load would go up to 99% as soon as the MAP got to 14.3 (which is what it reads for BARO). It still reads up to at least 24 PSI MAP (again, absolute pressure, not boost. There's been some confusion with 'absolute' in the past), but why would the load go to 99% as soon as it got to BARO PSI? Normally it doesn't go to 99% load until the MAP gets to 20 or so.
I also noticed that in 2nd gear at 1k RPM and about 20% throttle (rolling through a stop sign to keep from having to restart) the spark went way up to 7* ATDC. I had never seen anything later than 0* before. But normally I don't bog the engine down either.
I have never had to run a vehicle for more than a few minutes to relearn the idle, and I have never had to do it on a J body at all. I cleaned the IAC and passage a couple thousand miles ago, so I'm sure it's not sticking (and how it's acting it doesn't seem like a mechanical problem) Plus I don't know what could screw up the load reading. I also noticed the air bag light flashing 3 times at startup, which I had never noticed before, but it's possible that I only noticed it because there's a real problem now. I'll have to look that one up on ShopKey tomorrow along with checking codes. I have a used PCM coming from a local salvage yard that should be at the shop on Friday at the latest and driving it like this for 2 days isn't a concern at all, but I had told another member that I would trade him my GM SC PCM for his stock PCM. Did I ruin the thing or what?
Thanks,
Jason
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'04 Cavalier
2.2 Ecotec Supercharged w/ 2.9" pulley
Charge air cooler
Poly bushings - lower control arm and engine/trans
Well, some good news... got in the car this morning and it fired right up and ran 100% like normal, same thing after work too. Maybe the PCM just had to power down? If anyone knows what happened, I am still curious.
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'04 Cavalier
2.2 Ecotec Supercharged w/ 2.9" pulley
Charge air cooler
Poly bushings - lower control arm and engine/trans
Quote:
If anyone knows what happened, I am still curious.
you already know what you did
Quote:
So I'm sitting in the parking lot with the engine idling, when the read process
you're not supposed to do a read when the engine is running.
you may have tripped some form of theft protection.
sometimes they 'work themselves out' and go back to normal, other times you'll fry the thing and the best use for it is a paperweight.
be more careful because next time you may not be so lucky.
HPT can't do anything but datalog with our cars running. It's a sad fact of life. I'm glad you didn't fry something important though.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:Quote:
If anyone knows what happened, I am still curious.
you already know what you did
Yeah, I knew
what I did... I asked that wrong, I should have asked why what I did caused it to do what it did. The second part of your answer was exactly what I was looking for, thanks. I'm accustomed to using the Tech-2, Genisys, and MODIS at work, they all tell you before you do something stupid... and if you ignore it they won't continue. I knew the engine had to be off at some point, but after 7 years of waiting for the tool to tell me before the engine has to be off, I just figured I'd get a pop-up before I had to shut it off.
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'04 Cavalier
2.2 Ecotec Supercharged w/ 2.9" pulley
Charge air cooler
Poly bushings - lower control arm and engine/trans
