Chevy & GMC Vans

Just got a 98 awd that is in fantastic shape The van starts runs and shifts fine It has new plugs wires cap rotor fuel filter and a relatively new cat The problem is when I really try to push it up hill (60 mph and get on the gas) it seems to start to shudder and loses almost all power and seems to start to search around for or come out of gear It will then run really rough until I let off the gas for awhile It also has a general lack of power and seems to always be in a taller gear than it should Before the tune up this problem was significantly worse but now only happens when I push it a little I have not done a fuel pressure test but seems unlikly to be the problem or could it?

This thread might help CLICK

update--- did fuel pressure check seems 100% and did not go low at all when the problem is occuring also seemed to hold pressure fine after turned off for awhile does this rule out fuel system related? was suspecting my spider as I have read a lot about them on the forums but not so sure now :-k

As per your description of the fault I would be suspecting a plugged/restricted exhaust. This can be tested with a low pressure (10 PSI) gauge put in place of an pre-cat O2 sensor hole. A good reading would be less than 1 psi@ 2500 rpm. Or you an loosen off the exhaust at the manifolds & take it for a drive. If it runs good now then this confirms the exhaust is the source of the problem.

Thanx for the input v8famvan I was getting ready to throw in the towel and bring it to a shop my thoughts were it was timing related But I don't have a drop in the bucket of experience that you do I will try to do the psi test asap It has a new shiny cat welded into it I was wardering if you have any specific symptoms of a plugged exhaust as I live in Portland OR and driving around without the exhaust is not an option It also had an alarm that I disabled and the fuel gauge buzzes and the oil pressure gauge is kinda jumpy Thanx for your help hugely appreciated

Well I took it to a shop and it turns out bad compression in cyl # 6 When I got it back it had a noticeable exhaust leak at the manifold and runs terrible now for the big decision change the heads and have them machined at $250 myself or have it done for $1800

If you have the know how and tools to do it your self, the money seems to dictate doing that. Oh that and the time.

Well I have a torque wrench basic tools a Haynes manual and plenty of time The "know how" is suspect I have built several vw engines from the block up and was a small engine mechanic for a stint but this will be the biggest job to date if I decide to give it a try I am going to post a thread on the subject and see what I come up with Any advise?

That would be great to see.