HELP! .....what happened?

[LS1999TA]

Well the alternator died on the car on tuesday, right after i got the t-stat installed. i started working on it on friday night and while i was under it on saturday I installed an underdrive pulley too. Everything works with the excption of high RPM passes.

the battery was left unplugged for about 20 hours (if that makes any difference).

It pulls extremly harder on the lower end after the pulley, but 5000-5500 it kinda hesitates and 5500-6000 it falls on its face. (actually bogs down).

It used to pull smooth and hard all the way to 6000, but now it acts like its floating valves like a crappy 305 i used to have.

It seems to have better throttle response and rev way faster up to 5000, i was thinking that maybe its reving so fast the lifters dont have time to bleed down now and it might be floating valves........what do yall think?

[justinakajuice]

Maybe its not getting enough juice to the plugs......I've heard of problems with the 25% underdrive pulleys before. None from the 10-15% underdrive ones, though. I think you can check it by holding the wire away from the plug and revving the engine up to the rpm ranges you're having the problem and if the spark is weaker in that range, you might have a charging problem.

[LS1999TA]

thank you for the reply. thats a good idea, however, the only time i have seen it go below 13v is at 700 rpm(idle) with the headlights on & fans manually on high. I have this "floating" problem constantly......but i thought about that voltage idea as well.

[LS1999TA]

it revs to 6000+ fine with the clutch pushed in, but it only makes it to about 5500 during an actual acceleration.

[mr._bowtie]

And it just started doing this after the install of the under drive pulley? Did you do any other mods?

[LS1999TA]

t-stat and pulley.....thats it

[mustang muncher]

the pulleys have a history of messing with alternators and batteries where the alternator can't charge the battery very well.

[LS1999TA]

it has a brand new alternator. HAVE NOT seen it drop below 13V yet....... it swings up to 6G fine with the clutch in.....its only on passes!

[LS1999TA]

My car has no programming, however, i dont want that to be an easy excuse to close this thread, i'd like to know specifically what is causing this problem

[Lyle A]

Make sure you didn't knock a connector off a sensor or something like that.

[mr._bowtie]

This ones got me stumped... I cant imagine why your car wouldnt be able to pass up 5500 rpm. Adding the pulley should just make it rev easier, so that shouldnt be it. The pulley thats on it isnt rubbing against something would it? There could be something in the pcm that is acting goofy. Did you try disconnecting the battery for about 15 min and letting it sit then restarting it. I know that shouldnt be an issue becuase you just changed the alternator but ya never know. I would pull the pcm fuses as well.

[mustang muncher]

I guess i should have read the entire thread i was thinking ur battery wasn't charging. My bad. SInce its doing it only underload i would have to vote that it has to do with the drivetrain like u stated it might be that have some valve float happening.

[mr._bowtie]

Its possible that the clutch is slipping but usually if the clutch is the problem it will slip at low rpm as well as high. Generally speaking youll notice a clutch slipping right after you let the pedal out and the clutch re-engages. Not once its already clamped down and has been for a while.

[LS1999TA]

put the stock pulley on and it fixed it