serious throttle hesitation around 35mph

[typhoon1588]

okay, before i begin, please understand that everything i am writing about has been realyed to me from 300 miles away from my father, since i am up at school and far away from my typhoon.

anyways, apparently this thing has lately had a pretty dramatic throttle hesitation around 35mph. From a stop, it pulls pretty normally. At around highway speeds, it is fine. But if, say, the truck is being driven around at about 35mph or going onto a highway entrance ramp, upon hitting the gas, prior to and into boost, the engine feels like and sounds like it is only on 5 cylinders. After a relatively small RPM band, it sounds fine again.

Already, the ECM, fuel pressure and Torque Converter have been checked and ok'd. Plugs, wires, and fuel filter have been replaced with all the correct parts (they were okay to begin with).

Any ideas what might be the cause of this, and what to start looking into to fix it. Right now, the guy who is working on the Typhoon can't seem to find the root of this problem. Thanks,

 

[typhoon1588]

help? please?

 

[TyMeUp]

Sounds like more than one cylinder is misfiring.

What is the tachometer doing at this time? If it is going 'crazy', that's a good sign you have an ignition problem. Check cap & rotor for carbon tracks - worn-cracked rotor button. if OK, bolt on a known good coil.

If that doen't help, 'sweep' test the TPS looking for a dead spot. Also check that the EGR valve isn't hanging open. You can temporarilly disable by unplugging the electrical connector to the normally closed EGR solenoid.

 

[Bill Z]

serious throttle hesitation around 35mph

Mike,

If your dad has not found his problem yet, have him check a few things.

1st. Check all vacuum hoses for cracks. Cracks cause the air/fuel to be on the lean side.

2nd. Check the spark plugs and wires. If the plugs look questionable, replace them. I had a bad wire (#1 Cylinder) that had a burnt spot and only arced under acceleration. I was running a MSD box.

3rd, Like previously mentioned, the TPS could have developed a bad spot. This can be checked with an Ohm meter. It should be a linear increase of resistance.

4th. Check your fuel pressure at the time of hesitation. I doubt that he is having a fuel problem but it should be noted.

I hope one of these suggestions help.

Tell your dad Good luck.