loss of power

I have a 95 astro with 128K I recently replaced the fi spider and cleaned the egr . my problem is when i start it in the morning it runs great but when it warms up it seams to almost lose power when trying to accelerate past maybe a third throttle almost like its not getting enough gas. I replaced the fuel filter because i thought that might be it but no change. Any Ideas?

first thing to check is for a plugged exhaust, usually the cat breaks apart and jams it up.

when i get it reved up with my foot in it, it doesn't go as good as it should but it does go. I thought if it had a plugged exhaust it would fall flat on a rev.

has anyone heard of a knock sensor going bad and causing this?

I haven't. But after seeing the link you posted in that other thread.... It sure seems like a possibility.

I recall reading an older thread in this forum regarding a bad knock sensor causing this problem. I think it is a distinct possibility.

I plan to replace mine (if I can find the dang thing). Based on the diagrams I have of where it should be, I find only an empty threaded hole in the back end of the block. There is also a white wire and connector coming off the ignition coil with nothing attached to it. I'm beginning to suspect my father's trusted mechanic removed it entirely. Or I could just be suffering from temporary blindness.
Anyway, once I get it replaced (or reinstalled) I'll let you know how it comes out. :banghead:

I think the KS should be found on passenger side of the block. At least is was on my 89 Caprice, since the 4.3 is based off the 350 block, I assume it would be in the same place.

The wire at the coil is a tach signal. Unused on the Astro van. Well I used it to run my tach...

Ok, found the knock sensor and replaced it. It did help with the power noticably. I've still got some misfire problems. So the knock sensor wasn't the sole problem.
Good luck Mac

thats great about the knock sensor. I'll try that as soon as I get a second and let you know how it goes for me as for your missfire problem this may help...

http://www.obdii.com/ubb/Forum1/HTML/001357.html

Thanks, I saw that link in your other post. Ton of information there.
Reading it is what made me suspect my knock sensor. My 89 gets up and goes now. I've got water and steam coming out the tail pipe and some slow coolant consumption which points to intake manifold gasket or head gasket. I think the remainder of the misfire problem is related to this. I'll leave this one to my mechanic.

I did the usual things in chasing this problem -
new plugs
new distributor cap
new rotor
new wires
new ignition coil.
new pcv valve
After reading the thread in the link you posted, I started checking wires and found some evidence of arcing from the coil ignition wire, although I believe this was from the previous set of wires.
Thanks again.

mac, you ever solve your problem?
Thought I'd throw my last bit of info your way.
My egr valve wasn't clogged and "looked" to functioning ok. Bought a new one and pretty much figured out the old egr valve was just worn out.
This helped with the idle when cold, and smoothed out the acceleration quite a bit.
The pig still idled rough when the engine got hot so I changed out the coolant temperature sensor this morning. That did the trick. no more rough idle when hot. Doesn't dog on acceleration anymore.
The opposite of what you thought might be happening. It might be getting too much fuel when warm. Your's is a later year model than mine, so there may be more than one temperature sensor.
Good luck.

hrmm i just read that post about the knock sensor at 80,000kms and i think that might be whats wrong with mine considering that it has 579,000 kms and its never been changed i think itll help quite a bit thx for the post they've helped alot

with a Timing light check and make sure that timing mark is advanced 11 degrees at 825 RPM in Neutral or Parking. if is not, make the necesary adjustments.

hi guys sorry i havent written in a while ive been working constantly. i had the fuel pump go so it was replaced and that didnt repair the problem. scince then i got a full size van for my buisness and havent been using the astro, you know how it is - out of site out of mind

Yup know that well...
When you get back around to it, let us know how it worked out.