4.3 Random Sputtering/Stalling

[Atokad]

I recently picked up a '98 C1500 4.3l a/t. It seemingly drove just fine but I have found it has an occasional issue. After driving it for a while it will randomly lose all power and sputter and try to die when you hit the gas. The more throttle you give the worse it gets. It will backfire through the exhaust and sometimes even completely stalls out. This typically only starts happening after it's been stopped for a while like waiting at a stop light. If you don't touch the throttle it idles like normal, but as soon as you touch the throttle again it starts acting like it's choking. I have found that if you completely shut it off and turn it immediately back on it will run just fine again for a while. Seems like it may be a tps issue? Possibly crank/can position sensor? The entire fuel and ignition systems have been replaced recently. There is an engine light on for the O2 sensor since the previous owner straight piped the entire exhaust, however, the issue does not set off any other codes. There are no misfires present at all even when it's not running right.

 

[PlayingWithTBI]

1st thing, without O2 feedback you're running in open loop since the PCM doesn't know how rich/lean it is. That has to be fixed. Even with open pipes, a heated O2 should work.

2nd thing, get a scan tool or some way to data log so you can see what it's doing when it stumbles/dies.

 

[Atokad]

1st thing, without O2 feedback you're running in open loop since the PCM doesn't know how rich/lean it is. That has to be fixed. Even with open pipes, a heated O2 should work.

2nd thing, get a scan tool or some way to data log so you can see what it's doing when it stumbles/dies.

O2 was working, I can read the values coming from it. I have since put a spacer adapter on it and it has gotten rid of all the codes completely. I have had a scan tool on it the whole time and everything looks just fine which is why I'm having so much trouble. Every single sensor reads just fine and acts like it's supposed to. Been messing with the scanner for days and have had an actual technician help me and we're both stumped. Was hoping someone might've had a similar issue.

I know the transmission isn't in great shape so it's the only other thing I can imagine is an issue right now. Is there any way the trans can cause it to act up like this? It seems unlikely but I've seen crazier things happen. It has some minor slip issues right now but I'm wondering if there's anything else going on with it that might be the root of this problem.

 

[evilunclegrimace]

Fuel pressure, fuel pressure.