won't boost when warm

[Beefmalone]

I just picked up a '99 Lariat 7.3. It runs fine just putting around, but it won't boost up properly. As long as you're just driving normally you don't really notice, but if you floor it to pass someone there is just no extra power. It doesn't smoke or make any weird noises. No blowby in the engine either. My buddy is a Ford tech, but usually only works on 6.0s. He dropped the tank and replaced the in-tank sock and says he checked the turbo as well. He doesn't know what else to do without throwing parts at it. Said the fuel pressure at the engine is fine as well. Also, it boosts up fine when cold. Only starts acting up when the engine is fully warm. Made a quick vid.

You Tube

You Tube

Ideas?

[Beefmalone]

anybody? Bueller? anybody?

[Turbostang500]

Are you sure that it isnt building boost?

I have to watch the vid again when im on my computer (cant hear dung on this phone)
But it seemed like there is something holding it back.
heck does it have a cat on it? That might be plugged up.

Do you have any gauges to monitor things (boost, egt)?

[Turbostang500]

ok just watched it on my pc.

I am more curious now if this thing has a converter on it. It kinda sounds like the exhaust is plugged up and not letting the engine breathe.

at first I was thinking maybe a trans problem or brakes not releasing but now not so sure.

gonna wait to hear back from you as far as some feedback.

[Beefmalone]

Thanks for the help. I'll take a look tomorrow and check. I guess maybe "won't boost" isn't exactly accurate...more like "won't accelerate" past a certain point. Just not sure why it acts fine when cold though. I'll look tomorrow for a cat and post back. thanks

[jesilvas]

What was fuel pressure at idle then at WOT?
You'd have to watch boost levels, ICP/IPR levels at idle then WOT too to diagnose any further.

[Turbostang500]

I dont know about diesel cat converters but gas ones will change when they are hot and start becoming a restriction.

A couple tell tales would be extreme heat before the cat and alot cooler after.
you could also gauge how much air is coming out of the exhaust compared to another psd.

This is all if you do have a catalytic converter on your truck. Some came with them and some didnt.

[Beefmalone]

I called myself looking today and didn't see one. Shot a quick vid.

1999 Ford F250 undercarriage - YouTube

1999 Ford F250 undercarriage - YouTube

[Turbostang500]

Hey i dont think i saw it either but it will be further forward before the trans crossmember.

Since i dont think it is there, i would go with jesilvas and start diagnosing the fuel system.

Something definately isnt right!

Get a gauge in the fuel system and mount/tape it somewhere you can watch it while driving.

[the trav]

definitely no converter.

you need to watch the ICP/IPRcommand% and find a way to watch your boost and fuel pressure.

that should tell you all you need to know.