I've been working on a 97 12 valve, it has no power at all. it takes it 2 miles to get up 70mph. any ideas would be great. They said they took it along time ago for a bad head and it hasn't had the same power since but that was 70,000 miles ago and it is getting worse pulling a horse trailer it will barely run 60.

 

What other symptoms do you have, black smoke, white smoke, odd noises, etc? Bad head would be easy to check for with oil in the coolant or coolant in the oil, but wouldn't cause a huge decrease in power unless it was really bad and leaking horribly.

Low power is usually caused by lack of fuel (clogged fuel filter, bad lift pump, injection pump out of timing) or lack of boost pressure (clogged air filter, torn/loose intake boot).

 

There is no oil in the coolant it only black smokes a little when you punch it the lift pump is working new fuel filter I checked the timing, new air filter. I t doesn't have boost gauge so I don't know what the boost is but it never seems like it has any. I know no fuel no boost but could the wastegate be stuck open and not letting it get any boost?

 

check the turbo wastegate it should move with 10psi air pressure,it may have a blown waste gate valve.you will hear it leak.also check the pressure
relief valve on the fuel pump ( in the return line off the pump) if it has a broken spring the check ball stays open and won't let pressure stay built up.
also consider the possiblitiy that the injection pump may need to pulled and sent out for a major recalibrration.if it has never been done do it.these were famous for coming from the factory with the internal timing not set to spec.or the fuel delievery was set real low.if you send the pump to a bosch pump dealer/rebuilder and ask for it to be recalibrated to the top end specs you will be amazed at the difference in preformance. good luck quindel

 

Check the throttle travel first, make sure its hitting the stops. Its possible you have a stretched or frayed cable.
Then check the overflow valve, then check the wastegate.

 

Thanks I will check that.