reeseleblanc

OK. Wits end here. I just changed the plugs and wires. They were WAY overdue. I thought the previous owner changed them when he built the motor. Nope. The wires had 6/13/12 written on them. Daaammn. LOL.

Anyway, the car is acting up. At idle, I'm seeing 14.8-15.0 when I was seeing low to mid 14s.
At cruise, I'll get around 25% throttle and the car will stumble a little. When it does this, the AFR will bounce between 12.9-15.7.
If I go WOT, the car does perfectly fine.

I tried unplugging the MAF. The car ran a little better but still had the stumble.
I tried unplugging both O2 sensors, thinking the car would run rich. Nope. at cruise, it was reading 15.5.
I tried unplugging both the O2 sensors AND the MAF. The car went to 9.5.

I tried reloading my original tune thinking that something might have become corrupted. Nope. Same issues.

I don't want to just throw parts at it.

Engine info: LQ4 bored 30 over. mild cam. full exhaust. Rear O2 deleted. LS3 heads and intake. LS3 throttle body (built in TPS), Pretty sure the MAF is the original LS6 (3 screws to hold it in place, air temp sensor built-in).

Any thoughts?

isis

iTrader: (1)

reeseleblanc

I hooked HP Tuner up and looked at misfire events. Cylinder 1 was showing triple digits while the others were at zero. I went to Walmart and got a new battery (Maxx 78S). The car started slightly faster than it normally does and it seemed to be running better. Another look at HPT showed all cylinders with zero misfires. I suppose it's possible that the battery was bad and causing electrical gremlins? Now that I've changed the battery, the temp gauge isn't registering anything but I found a few mentions of this being normal. It should come back to life in a couple of days.

I'll keep an eye on it for the next day or two but I think the car is back to where it needs to be.

jmilz28

iTrader: (13)

Clean and retighten ALL ground wires.

Also possible the plug wire on cyl 1 was just not perfectly seated. I'd pull it, regrease it, then re-seat it...make sure you get the click.

lollygagger8

iTrader: (7)

^this^

kra86

What year chassis is this car?

reeseleblanc

And now this...
I drove to work with no problems yesterday. I went to the car to leave and the dash lights up but nothing happened when I turned the key. No fuel pump. No crank. A few seconds later, my Service Theft System warning came in. Crap. I had my wife bring my other key. No difference. I tried unplugging the battery, etc. Nothing. I had the car towed to my buddy's shop and he got me with the news... Pcm is totally done. He swapped it into his car to double check... Nothing. No communication. Dead.

So... Do I have to go with a specific PCM or can I use any 411 or 896 PCM as another friend said? Obviously, the later choice is cheaper and easier to acquire. I just don't want to hit a snag running an improper computer. I'm pretty sure my current PCM displayed as being something other than the original one when it was scanned in HP Tuner.