gutless towing?

2008 expy. I recently updated all timing components, rollers and cams included. Melling 360hv oil pump as well.

On regular trips, fuel economy and power seem back where they were before, but towing a travel trailer or boat, the top end seems lacking. On flat highway, it feels like it pulls fine, and bottom end power seems good, its only when going up grade that it sucks. I capped out at 50-55mph going up a 8% grade pulling probably 5-6k pounds. Fuel economy is also low when towing (versus before, a few years back)

its got around 196k, i just replaced O2 sensors, didnt seem to make much difference, plugs are relatively new.

Using a scanner, power contribution test did not show any misfires or cylinders of concern. Relative compression check was also good.

Fuel pressure is 65-70psi... 70psi at idle, 65 being worst at full load, high rpm.


Could it be a clogged cat? that would explain why high rpm seems lacking, but low rpm seems better.

Vdubnick said:

Could it be a clogged cat?

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get a laser thermometer ($20) and check the temperature (while hot) before and after the cats.

Yupster Dog said:

get a laser thermometer ($20) and check the temperature (while hot) before and after the cats.

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great idea thank you... i have one, even have a thermal camera, not sure why i overlooked that.

ill check next time i run it.

Our 2013 5.4 truck is a turd with a trailer behind it. I finally committed to a 5 star tune and exhaust mods. I'll update in a few weeks, I'm pulling a car from florida to south Carolina . Really hoping the tune improves the throttle response and the shift schedule.

I’m pulling a 30 ft 4920 dry GVWR 6500 trailer with my 2008. The only time I noticed overheating was when I was dragging the trailer out of a canyon and it was very minimal on the gauge. Might want to look into a regear to something deeper. Not saying it’ll be a draft horse but it may help engine and trans strain. I noticed that mine would ramp up to 3000 rpm with O/D off and it would hang around 2000 on flat pulls or in hilly country with O/D on.

My truck has always sucked towing more than ~3k or so up hill, though it sucks slightly less in tow/haul mode (missing on '08 obviously). Was there a time when it towed better?

Towing is why I got my 17, the Ecoboost is way better for it. The thing I've learned with the 4.6, 5.4, and 6.8 is they need to rev. Don't be afraid of 5000rpm when towing, that's where max power is anyway. The power curve is from 3700-6000rpm. In the mountains my RV is always above 3500rpm.

ManUpOrShutUp said:

My truck has always sucked towing more than ~3k or so up hill, though it sucks slightly less in tow/haul mode (missing on '08 obviously). Was there a time when it towed better?

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yes, 3 years ago when we first got the trailer, got 10mpg on a 300mi trip, mostly flat highway, towing without a an equalizer, so the ass end was overloaded for sure. then the next two years, same trip, got 8mpg, and then almost 6-7mpg. wind was not a factor.

i do question the cat, as it may have had fueling issues due to the failed timing components, or the warped RH manifold...

oh, and my 08 does have o/d tow/haul mode. it just keeps it from going into OD, avoiding the frequent downshifts if the ground isnt flat

Timo2824 said:

Towing is why I got my 17, the Ecoboost is way better for it. The thing I've learned with the 4.6, 5.4, and 6.8 is they need to rev. Don't be afraid of 5000rpm when towing, that's where max power is anyway. The power curve is from 3700-6000rpm. In the mountains my RV is always above 3500rpm.

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oh i totally understand that... it just feels like the high rpms (4.5-5k) have same power as at 3k. downshift wouldnt bother me if it felt like it was making power.

Roast4570 said:

I’m pulling a 30 ft 4920 dry GVWR 6500 trailer with my 2008. The only time I noticed overheating was when I was dragging the trailer out of a canyon and it was very minimal on the gauge. Might want to look into a regear to something deeper. Not saying it’ll be a draft horse but it may help engine and trans strain. I noticed that mine would ramp up to 3000 rpm with O/D off and it would hang around 2000 on flat pulls or in hilly country with O/D on.

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yeah, i was worried about that on the hill, its a couple mile stretch at grade, so i kept an eye on temp, i was surprised there was no change.