Sputtering under load

[Kenneth]

My son's Bronco ll with a 2.9 sputters under load hot or cold . It feels like it is not getting enough gas checked fuel pressure has 30 to 40 psi when running. We have replaced the catalytic converter, o2 sensor, the module on the distributor. Also checked all vacuum lines for leaks, still sputters .

 

[RonD]

Welcome to the forum

I would suspect partially blocked exhaust, but I assume you checked muffler when Cat was replaced

Fuel pressure seems OK, but check again and raise RPMs to 2,500 and hold there for 30-60seconds and see if pressure is slowly dropping, which would be weak fuel pump(s) or dirty fuel filter

Put a can of Seafoam in gas tank to clean injectors, or pull them and clean them

Was this a sudden issue?
Or was it slowly coming up over time?

 

[Kenneth]

Came on over time and has been getting worse. My son has been using injector cleaners along with Marvel mystery oil. I will recheck the fuel pressure. Right now there is no muffler

 

[Kenneth]

Fuel pressure staying right at 30 to 35 psi. But drops off to 10 psi after 10 minutes after shutting off

 

[dvdswan]

So does the psi drop when under load then? If not, I would look at the electrical side. Spark plug, wire, coil may seem fine at idle but can also break down under load and over time.

 

[McWillies]

I'd check spark plugs and wires before messing with anything else. It's usually the stupid little things that everybody thinks aren't the problem that turn out to be.