AdsoYo

iTrader: (1)

Lately I've been having a horrible time with this P0353. Car is a 24x LT1 TransAm so the code is actually for cylinder #2 not #3. This happened before last October with the same code. It would actually start missing during normal driving and then fix itself shortly after. I replaced the coil anyway and haven't had problems until these last 2 weeks now that I'm driving it again since the snow is gone and it's dry out.

I took the car on a 250 mile round trip and it did great until just before getting home, I noticed it was missing. Hptuners showed a P0353 again. Checked plugs and noticed #2 was dark so I put a brand new coil in, checked all wires and got 40 ohms on all of them, changed plugs to TR55's gapped at 0.055". It ran fine for a about a second then started missing again.

Put my last new spare coil on, didn't make a difference. Checked the coil harness and got continuity on all wires. Checked continuity from connector at coil #2 to PCM and it was fine. Although I couldn't find the 12v reference pinout on the PCM if anyone has that info.

So the other day I changed out the fuel injectors to stock 24#ers (I was troubleshooting a separate minor issue that these injectors didn't fix) and it ran fine for the 20ish minutes I drove it. Put my 30's back in randomly and it drove fine again until today.

Now I attempted to drive it again and it ran fine for about a minute then started missing, P0353. So I came back home, swapped coils with a good cylinder, made sure all wires were connected nice and tight and tried it again. Worked fine for another minute so I went WOT real quick and came to a stop for a light. When I tried to go again, it was missing. P0353.

I don't know what else to do besides try a new PCM. Harness is from BP Automotive so it's new and constructed well. I'm using AC Delco D514A coils, MSD wires, 0411 PCM from EFI Connection.

jimmyg

Do u mean ls1? Lt 1 has opti spark I thought. If it's an ls1 try a crank relearn. So times the crank sensor ***** up and u will get a misfire code .actually just googled it. It is coil 3. Bad coil or open circut. Or bad pcm.try swapping coil 3

AdsoYo

iTrader: (1)

I converted to 24x meaning I'm running an LS1 PCM with coil-per-cylinder ignition. Since the LT1 has a different firing order than the LS1, cylinders 2 and 3 had to be swapped in the wire harness. I don't think a crank relearn will help because I really am getting a miss on cylinder #2. I can't think of what else to try besides another PCM but how common is that for a PCM to cause a problem like this?

jimmyg

Well when I looked it up bad pcm was cause no 3. try another pcm if u can get one cheap. Just saw one on e bay 90$

AdsoYo

iTrader: (1)

Yeah I just did a bunch of searching and found one guy in a thread from 2014 who said he had intermittent misfiring on #5 that kept getting worse and swapping PCM's solved it. They even put the PCM in a different car and the problem followed. Unfortunately I don't have anyone around here I can swap PCM's with so I'll probably just buy another one. I saw ebay had them for cheap but I want a little more piece of mind so I'll be buying from EFI Connection for $200. Still better than $350 at rockauto.

AdsoYo

iTrader: (1)

Bought a remanufactured 0411 PCM and have been driving with it for a few weeks now and no more P0353. I heard these PCM's are good for around 1000 flashes so maybe I hit that limit since getting HP Tuners on my problematic PCM.

Pop N Wood

iTrader: (1)

Good to hear you resolved the problem. I was betting on an intermittent connection in the harness.

Thanks for closing the loop and posting the solution. Hopefully you save someone else from future problems.