I just rebuilt my 92 ton dually 454. Before the rebuild it had the same problem. truck runs and idles good. When on the road unloaded under normal acceleration it will pick up speed like it should. Cruising along at say 55 and go to WOT the truck will shift down like normal but will not pick up speed or RPM. if you let off to about half throttle it will start to pick up speed/rpm. Like said it is a new motor with new O2 sensor and coolant sensor. Any suggestions? It gives no codes. Thanks

 

I would check for clogged cat or low fuel pressure

 

Cat was my first thought. However I cut it off before the rebuild. it has open headers now. As far as the fuel pressure i checked it(the best I could with the inline adaptor) it was reading about 10 psi at Idle. i havent seen any fuel pumps not have low flow as suppose to low pressure or nothing at all but Im leaning toward a fuel pump as well.

 

11 psi is stock for those trucks.

Anything done to the engine over stock....might need a chip to dail in the engine. However, fueling issue could be solved by getting an adjustable pressure regulator and bumping it up to 13 psi to see if that helps.

What type of air intake are you using...if you have a stock tubing...change it out for an open air element since you said you have headers.....

 

You can have pressure without proper flow. I would do the following. 1) Replace the fuel filter with a name brand filter. 2) If that does not cure the problem, get a fuel pressure gauge with a hose. Hook it up to the test port, make absolutely sure you do not have a leak, run the hose to a place where you can observe while driving. Take it for a test drive and watch the gauge and then push it to the limit. When your truck starts to act up, see if you have a reduction in fuel pressure. If the pressure is stable, you have another problem. If not, look at the fuel pump and sock in the tank. 3) In that vintage of trucks, the pickup coil and reluctor wheel were considered to be a "maintenance item". The p/u coil had a decaying magnet inside. If yours is more than three to five years old, replace it. 4) Lastly, did you rebuild your throttle body when you had the engine apart? Each injector in the T/B has a small screen inside that could have dirt and rust inside restricting flow. The rebuild kits are cheap and the job is pretty easy and straight forward. Good luck with your truck, hope this helps!

 

Thanks for the info. Im gonna try a fuel pump, Have already got one ordered. even if it not be the fuel pump Ill be inside the tank to see for leaks or bad hose inside the tank. as far as the injectors I dint know they made a rebuild kit for Tbi throttlebodies. While Im at is I may go ahead and stick a pickup coil in the distributer, I know they do give a lot of trouble on the Tbi stuff.
thanks Fellas
Ill update when I get the pump in

 

BTw It still has the stock breather on it with the Intake tubing deleated.

 

Napa or Oreilly should have a rebuild kit for the throttle body. Its just gaskets, injector orings and most importantly the injector screens. Also comes with a new fuel pressure regulator diaphram.


I would suspect a pump issue. Fuel is critical for a TBI engine to run right. They will run on as little as 2-3 psi but want to stall and stumble with any amount of load applied. I would suggest setting the pressure to about 12 psi if you can. The easiest way to bump the pressure up is to drop a quarter in under the fuel pressure regulator spring before you put the regulator back together.

 

^I guess that would work. ILL try that

 

Idling it will act a Lil funny cold. once warm no funny hesitation at idle when barley touching gas like 2to300 rpm worth. But cold or warm starting at a stop bout 1/4 inch into the throttle I have hesitation then it's fine thru 3/4throttle response wise and power wise seem fine.at wot it falls on its face. No power. But engine roars but no gogo but listen if I back off 1/8 of a inch on that throttle at wot it will catch perfect and take off like a bat outta he'll. What has been replaced is Plugs wires distributor that stupid part within the distributor before I replaced the Distributor All 3 current temperature sensors because one was throwing a code and we're in a code and I didn't know that the 454 had 1 for an electric fan so technically it has 3 versus the normal 2 I learned my lesson that was a pain i* t** a**. The coil's been replaced PCV valve's been replaced even though it seems to be good New injectors Tbi rebuild kit I've had 0 codes except the 1 for 15 which is for the extra electrical fan that the 454 has for current temperature sensor When I put the near distributor in I've never time to vehicle so I took it to a shop and paid 60 bucks he said I was one tooth off I felt pretty proud about that being a certified YouTube mechanic I've seen this post I've seen it before I found it again 6 months later same problem can't figure it out tired of throwing parts at it what do you all think This has the EGR before it had a sensor the sensor that is connected to is that stupid filter filter filter filtration system one that has the tiny little air filter in it but again I'm not throwing any Coats so I'm at a wash on what it could be And I get a feel smell and heavy fumes from the exhaust when I'm hard on it only Exhaust does smell pretty rich