kapedogg

iTrader: (5)

Here's my story, I had this same problem before, and took it to a shop that got it up and running again about 3 months ago. The car would sputter and sometimes jerk hard under light load around 2300 rpms. They found a little leak in the intake, swapped the coolant temp sender, the plugs and wires, and also the PCM and retuned it. When they would drove the car, and it would start to sputter, and their computer read out would show no values whatsoever.

Now the car is doing the exact same thing! Last Friday I went to the track, the car ran fine, no problems, and it started acting up today out of nowhere. I have driven just a few miles here and there since the track, and the only change from before is that I ran a cut out at the track and hadn't put the blocking plate back on yet. Could that possibly be causing this? I'm going to check the plugs/wires tomorrow when it's light out.

Thanks for your help guys.

BigBadWolf

Anything like this?

https://ls1tech.com/forums/pcm-diagnostics-tuning/286823-hesitating-miss-fire-something-else.html

jimmyblue

iTrader: (11)

If they swapped the temp sender then they might have
been seeing bogus temp readings (presuming they had
tried to read anything?). Bad ECT data will really jack
your spark and open-loop mixture around. ECT also
determines whether your part-throttle is open or closed
loop. Thing is it's just as easy to get bad data from a
bad connection as a bad ECT sender; probably more so
in fact, since the sender is basically a protected hard
piece while the connector just hangs on by a spring
contact and the wire can easily brush a header tube, etc.
Intermittent action like this indicates something loose
and I've seen this particular thing. Try pulling and reseating
the ECT sender connector a couple of times and inspect
the wire at least as far as it's outside the wire-loom.

But a cutout left open and driven at low speeds also has
the potential to bend the closed loop fuel trims by fresh
air reversion, if it's within a couple feet of the front O2s.

kapedogg

iTrader: (5)

Before they swapped the ETC sensor and put on a new "pigtail," the temp. gauge was not working at all. After the swap, it has worked fine, and still is working fine, but I'll be sure to check the wiring after work today, perhaps the wire sending the signal to the PCM but not the gauge is burnt.

The cut out is located in the piece of pipe just before the cat-back. I probably drove it 10 times or so just 3-5 miles a trip. The first time it happened, I was fighting traffic for about 30 minutes, parked, and then it had trouble getting started and the rpm's jumped around a bit. On the way home, it started sputtering again like last time.

I did a quick visual check before work today of the ignition wires, which all seemed to look ok. Tonight, I'll pull the plugs I can get to and see how they look(maybe I'll get lucky). I originally had Taylor 10.4mm wires, which became "stringy" at least that's what they said, so they put on a set of stock wires they had lying around.

By the way, here’s my setup: Lingenfelter ported/polished LS1 heads, GT2-3 cam, Ported Throttle Body, TR-6 plugs, Air lid, Mac mid lengths, ORY, Borla, Free mods including removal of EGR/AIR. TNT wet kit installed, but never used. Various stereo equipment with 2 amps.

Could the amps pulling on the alternator/battery have anything to do with this?

kapedogg

iTrader: (5)

Reinspected everything visually, and it all seems fine. Realized I don't have the right combinations with my ratchet set since I moved and couldn't pull the plugs. Still no SES codes. The wiring to the ECT sending unit looked alright as well.

Could something be shorting out the PCM or maybe I fried it somehow? After they fixed it, the car has ran fine for about 3000 miles.

Any ideas on troubleshooting this? I'm afraid the only shop I know/trust since I moved might not want to work on it again.

I took it for another drive, and it was alright under light load, shifting around 2100-2600 rpms for a few miles, then I hit the highway and gave it half throttle/full throttle and it stumble at 2600 rpms, 3500 and 4000 rpms too, but pull alright in between. Under normal driving around town, it typically stumbles under light load around 2500-2700 rpms. These are the exact same symptoms as last time, there really has to be a simple explanation for all of this! Please help guys. Here's a long shot, but is it possible that the computer somehow lost its tune?

Also, the first day it happened, it was about 80 degrees and I was fighting traffic for about 30 minutes so it was getting pretty warm under the hood, but nothing exceptionally hot.