Sputters/Dies when warm 2003 SS
 

Hey, I really need some help as I’m stumped! I have a 2003 SS 3.8. About a few months ago, the car started to all of a sudden sputters and dies. Seems to only do it when at operating temps. It’s always started back up except for yesterday. Had to let it sit for a while and then started back Up.

I have changed the fuel pump, the filter and the fuel pressure regulator. I hooked a scanner to it and there are no stored or pending codes.

Today, just to trouble shoot, I started it and just let it idle. About 30 min in, it died. I started it back up, needed to feather the gas but it sputters and dies. Let it sit for a few min, started right up and ran great for 45 minutes until I called the quits. I have no idea where to go with no codes and the car runs great until it has an episode.

my only shot in the dark right now is a ignition control module

Do you have a scan tool you can log with?

Id log the main sensor data when it usually happens and see what the sensors say when it stalls.

If not, I'd try unplugging the MAF and see if it happens without the MAF plugged in (it'll fuel based on the MAP sensor instead). Its not uncommon for a MAF to work totally fine, freak out, then go back to normal a second later after the engine has stalled / when restarted.

I do have a scan tool and I can monitor some readings, but nothing seemed off. Unplugging the MAF made no difference, it acted the same way.

What it seems like to me, as the car sits and runs, up to operating temps, something just happens and it dies.

I can start the car, but a few times when I was testing it, it won’t run unless I’m feathering the gas pedal. And with that it runs rough, almost like a miss.

no codes…that is what’s frustrating.

Are you able to post the log of the sensor readings just before it dies / when its running rough? Thats about the only diagnostic data you can send to help us review.

You mention it feels like its missing on restart- is the pcm adding those to the misfire counter? What do O2s + fuel trims look like when it's doing this?

Sounds like you'd previously identified a fuel delivery issue, have you confirmed fuel pressure is in spec, especially when the issues occur?

I wouldnt be too worried about the code thing anyways - since you've got access to the sensor data, you've got all of background info it uses to pull from, just means it hasn't tripped a threshold to trigger a light yet. If its something like an intermittent open in the icm, the pcm isn't going to have visibility to that anyways.

Its clearly losing spark or fuel, so IMO step 1 is confirming which. As you'd spent a lot chasing a fuel issue already - Id check to make sure fueling is rock solid when it occurs / that you fixed whatever issue caused you to deem those parts bad. Narrowing it down to one system will help greatly narrow the suspect list.

The air filter is new. Seems to be a heat related problem….shows its head when the car is fully warmed up.

If your scan tool can monitor each injector, I would pay attention to that when the issue occurs. It could be a faulty injector. I had a mystery issue on my 1991 Firebird with a 3.1L V6 that was fairly similar to yours and after the shop attempted to "fix" it 3 times I did some research and discovered that fuel injectors can intermittently short out and won't throw a check engine light. Any kind of intermittent issue is difficult to track down especially when there's no check engine light. I was tired of messing with it so in a last-ditch effort I bought a set of 6 rebuilt and flow-matched fuel injectors, replaced all of them and never had another problem. Before going through that work though, I would first hook up a scan tool and monitor the spark to see if there are any misfires that occur when this happens. Coil packs can also present issues when hot that may not show up when they're cooler. I'd put my Vegas bet on either a problematic injector or problematic coil pack. Good news about doing the injectors is you can take care of your valve cover gaskets, replace your upper intake manifold (I recommend ATP) and gaskets, and replace your plastic coolant elbows with metal ones while you're in there. That's like 4 birds with one stone.

One more thing I forgot to mention yesterday. Also check your crankshaft sensor. There was a guy on here with a 3.4L a few years ago that had an issue where the crankshaft sensor would stop sending a signal once it got hot.