Bad pcm symptoms?
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
Bad pcm symptoms? I've been having issues with my car under performing after a fast 102 swap. Car has been having misfires lately. Cruising is in affected but idle and my track times are shot. When I roll to a stop the car idles down and sometimes won't catch itself stalling. My tuner can't fix the problem go figure. I went from trapping 116 with an ls6 to 108 some times slower. I know the car can't be running on 8 cylinders. Do these seem like bad pcm symptoms? Checked compression changed injectors and plugs. After the swap while writing a tune my tuners laptop died.. would that fry a pcm or are these cases too mild?
The only bad Gen III PCM I've personally experienced over several years, several cars, countless flashes and so on was my 2002 F Body that suddenly gave me an intermittent misfire on cylinder 5. I'm told the 1997-1998 Y body and 1998 F Body PCM's weren't as robust as the 1999 and up variants. I have never flashed a 1998 or older PCM so I can't say.
In short, in my experience PCM hardware issues are pretty rare.
If your tuners laptop died while flashing the PCM, this can cause odd issues (even a no-start condition) if the flash was corrupted. You probably need to do a complete rewrite of the PCM to recover it before attempting to swap parts.
In short, in my experience PCM hardware issues are pretty rare.
If your tuners laptop died while flashing the PCM, this can cause odd issues (even a no-start condition) if the flash was corrupted. You probably need to do a complete rewrite of the PCM to recover it before attempting to swap parts.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
This is where a wideband would be very useful. You might be going lean at WOT causing some knock which results in a reduction in advance. The combo of lean and reduced advance would cause a big reduction in power.
Were the injectors or the fuel system changed?
Any way to check the fuel pressure?
Were the MAF or MAP sensors changed?
Assuming your tuner has HP Tuners or EFI Live, he/she should be able to log a WOT run which would help diagnose this problem.
However, as suggested, getting a complete Write made to the PCM should be the first step.
Were the injectors or the fuel system changed?
Any way to check the fuel pressure?
Were the MAF or MAP sensors changed?
Assuming your tuner has HP Tuners or EFI Live, he/she should be able to log a WOT run which would help diagnose this problem.
However, as suggested, getting a complete Write made to the PCM should be the first step.
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
Sorry for the confusion. I do have a wideband the afr is 12.7 at wot. Injectors were changed to fit the fast. I believe I have a lazy cylinder on bank 2 plugs are new my steps to diagnose are coils wire and injectors swap. Just trying to get info on if the pcm could be bricked. After all my steps are covered.
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
I'm not saying start over with tuning. I'm saying do a complete re-write of the calibration he was trying to load when the laptop died. Stopping the flash in the middle can have strange and unpredictable results. If that doesn't work, then I would try testing / replacing parts. Start with what is free and simple.
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Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
my only concern is if the pcm did get damaged would it be so miniscule that it only affects fueling at wot or when not under load? like I said car cruises perfect wouldn't my afr be erratic? Just seems odd that an intake swap would do this much to a car I'm using proven injectors and new plugs, wires are the same as my ls6 setup. literally everything is the same besides the intake, tb and failed write while tuning. that's what worries me most. honestly car ran good even before tuning and the failed tune for being only tuned for heads and cam to adding the 102 fast little idle issues and leaner wot but no stalling whatsoever. that's what leads me to believe the failed tune made the pcm a paperweight.
I don't think it is bricked because it still runs.
I accidentally knocked the USB cable out of my laptop because it wasn't fully seated while flashing one of my 411 PCM's with HP Tuners. Car wouldn't start, fuel pump wouldn't enable at key on, etc.. I reconnected the cable and tried a write entire, it came up with a window that said "recovering..." A few moments later HP Tuners did an erase and re-flash which cured my problem.
I accidentally knocked the USB cable out of my laptop because it wasn't fully seated while flashing one of my 411 PCM's with HP Tuners. Car wouldn't start, fuel pump wouldn't enable at key on, etc.. I reconnected the cable and tried a write entire, it came up with a window that said "recovering..." A few moments later HP Tuners did an erase and re-flash which cured my problem.
OK if it still runs it's not bricked and you got lucky. Usually when that happens the boot loader gets wiped out. You need to datalog it to see what the performance issues are then.