Fuel pressure question

[iggy1718]

My truck is running pretty rough lately. Checked all teh electrical stuff and seems to check out fine.

Started to check the fuel pressure. At idel I have 29psi. When you rev the motor the FP goes up but if you hold the throttle open the pressure eventurally settles back to 29psi.
Shouldnt the pressure hold steady at the higer psi when the throttle is held open?

 

[aldive]

What motor do you have?

 

[iggy1718]

sorry 4.0 OHV. And those readings were in park in the driveway. I checked the TPS voltage and its checks out alright. Checked plugs and wires and fuel filter is pretty new. Is there any test I can preform on the MAF? this seems totally random. While driving it will just go away as if nothing is wrong and then come back as if all cyclinders are misfiring. We tested the coil against a new one and it seemed to be fine. Although the ohms on the primary didnt hold steady they just dropped off to zero on both coil packs.

 

[iggy1718]

hmm no response. Good thing I fixed it. Had a cracked spark plug.