its a 99 and a van.... and a p0171

[Chevy Express]

Guys,

looking for a bit of help. I have a 99 7.4 3500 express van cut away (motor home). p171, and severe bucking under load, when going over a bouncy road. 67k on engine. I have watched a ton of video's on the injectors and fpr replacement. What I haven't seen is one done on a van. Does anyone know if this is possible with an engine still in via the dog house.

ordered a FP gauge, guess I will start at the beginning, i get misfires across all cylinders. LT is +25%.

Any advice would be great.

 

[454cid]

Have you eliminated other problems? The PCM is seeing a lean condition on Bank 1, but misfires on all cylinders suggest that the issue is on both banks. Have you checked 02 readings, and considered vacuum leaks, or a dirty/bad MAF?

Injectors on the Vortec 454, are known to be a bad design, but they tend to leak which I would think would create a rich condition, not lean.

I just watched this video the other day, as I'm having a fuel issue with my Volvo.

xc_hide_links_from_guests_guests_error_hide_media

 

[Schurkey]

Misfire will cause a functioning O2 sensor to report a false "lean" condition. Fuel trims will be affected.

How old are the usual "tune-up" items--cap, rotor, plug wires, plugs, air filter, fuel filter, PCV valve? Does the AIR system work right (if equipped)? Does the EGR work properly?

How old are the O2 sensors?

What is the fuel pressure?