[rmfavero1]

When in 1st gear (not L), but 1st, the truck builds power quickly until the governed 2,300 ish rpms. Under full throttle, about the half the time it seems to cut out and smoke a little blue smoke at that rpm....sometimes it doesn't. If not WOT, it will rev smoothly and higher. In higher gears it doesn't stumble at all. Is the cutting out a simple function of the gsk, or do I have a leak or something?

 

[Evel486]

What model year and tranny? The governor will not cause smoke at cut-off.

 

[Boa550]

Check/Replace your Fuel Filter and blue smoke sounds like you need to let er warm up some more to operating temps before stabbing the go pedal. The stumble in a stock 94-98 non-VP44 pump will more likely be a fueling issue.

 

[rmfavero1]

Sorry. It is a 95, nv4500 ..... I need to add my sig. I usually do let it warm up really well, and I didn't think it was a fueling problem since it doesn't do it in any other gear, not even in L.

Thanks

 

[Boa550]

It sounds like an air leak. That is air is leaking into the fuel lines (hard to see) when the rpms rise. A fuel pressure gauge will determine if the lift pump isn't doing its job and needs to be replaced. And it should rev smooth to the governed speed and not stumble. The stumble or cut out is much like running out of fuel and the truck wanting to stall (done that so many times).

 

[rmfavero1]

Just to clarify, it runs perfectly smooth UP TO the 2200-2300 rmp governed limit.....it is beyond that that it will stumble sometimes under WOT. under 3/4 throttle, it will rev all the way about 3k smoothly.

Thanks for the help.....I had better install the fuel pressure gauge anyway and check for air leaks. I have replaced a couple lines for fuel leaks, but haven't tackled the air leak yet.

1995 4x4 5 speed, mostly stock.....