Well i have to look for help...having asked a few professionals only problem a,d seeing the cost per/hr ..i prefer to attempt this things on my own..I have 25 yr mech experience...my career in aviation ,jet engine an such..turning a wrench is nothing new....i also have reduilt many muscle cars and maintaining my own vehicles as much as possible.(save me alot of $$....)

this is my delema, i have the gret little truck...i have had only the heads off..rebuilt. now it will start on 1st turn over. and idle smooth as silk...but once in gear and takin off...it willact lick its running out of gas,,fall on its face..then rev up like it going to take off..then fals off again...20-30 mph max alll while doing this..NO CODES.?? this boggles me...when i stop and just let it idle ..its all smooth .no misfires..it actually runs better than before i had the heads redone..

what i have done.
disconnected the Cat..... still the same....disconnected the muffler...still the same ( this done to see if any were collapsed of clogged) ,fuel pressure is good..filter was changed,oil was changed. ..timing is set( preset by correct alignment of arrows on dist and such).
like i said "no codes" are being recorded... make no sense to me.
plug wires are routed correctly.. new plugs, dist and wires,,.

its a great truck..my son wants it..so we gotta fix it...

 

What year? What brand did you use for the tune up? Have you cleaned the MAF sensor?

 

1st off we need to know what year, make, model.

 

1998 Jimmy sls..v6 vortex


HX..have done everything mentioned...and finally after all this ..i fixed it...
i was going to remove the top half of the intake , to make sure my spider injectors were properly installed ..and thats when i saw it,,the metal hold down for the fuel injector lines ,into the spider assy .top of the intake..was installed upside down..the lines were not held down in the cavity complete..the shoulder on the metal piece must face down. NOT up....it can be installed either way.. and looks fine..
so at idle .just enough gas...but it was leakin inside the manifold..so u wouldnt see anything...wouldnt smell anything..no rich burn out the exhaust...just an engine lacking power to do anything..no codes..no lean misfire, or lean banks..nothin....
wow ,what a PITA....//and well now it runs like a champ at 120thou miles,