97 K3500 7.4l spitting, sputtering, backfires, and stalls

[Agibson]

Ok I finally got a chance to work on the truck. Replaced the switch wire on the the starter. It seems to run a little better so I decided to check the fuel pressure again while it's running at idle it was at about 46lbs. So question is that to low or about right. I can't seem to find a spec on it.

 

[Carlaisle]

That's way low. Spec is 58 - 62 if memory serves, although that engine will often run just fine on a somewhat lower pressure. 46 far exceeds the engineering tolerance for the "somewhat lower" range. The fuel pressure regulator, fuel pump, and/or fuel filter are the culprits to inspect/replace as needed.

 

[454cid]

Ok I finally got a chance to work on the truck. Replaced the switch wire on the the starter. It seems to run a little better so I decided to check the fuel pressure again while it's running at idle it was at about 46lbs. So question is that to low or about right. I can't seem to find a spec on it.

That's a little low. The 454 doesn't need as much as the 350, but that's still low.... I don't know what the actual spec is for the 454.

 

[Agibson]

Sorry it took so long but u finally got the fuel pump in. The motor is running better now, but I think I'm having transmission issues. It shifts fine but occasionally if I step on it it just won't kick down. It picks up speed just not very fast.

 

[Schurkey]

Connect a scan tool, look at transmission codes and transmission data stream. I guess while you're connected, also verifying engine codes/data is wise.

 

[Agibson]

I know it been awhile since I last posted. But you know life gets in the way. So I put a new pcm in it and got codes P0785, P0740, and tps code. The power wire for the transmission plug was already replaced from previous owner. So I put the old pcm back in and all but the tps code went away. It has a hard shift 1st to 2nd than a soft shift to 3rd. Then it goes into OD at like 30 mph. I'm just looking for somewhere to start testing any ideas would be greatly appreciated.

 

[Schurkey]

Then it goes into OD at like 30 mph.

Overdrive...or torque converter lockup?

 

[Agibson]

Overdrive...or torque converter lockup?

I believe OD because I give gas and it will pick up speed just really slow. If I put it in 3rd and it seems to be ok

 

[Agibson]

Ok I think I finally found the problem. I put a new pigtail on the TSP and ran new wires to the ECM for the TPS. And so far it's running good and shifting smoother than it ever has