2001 astro bucking before shift? not tranny

[Leconte]

Recently I started my own business and got a 2001 astro as my work van. So i've only owned it about a month. 155k miles 2wd. soon after getting it, i noticed it will hesitate and buck a little at the top of gears before shifting, i thought it was a transmission problem and went to the tranny shop i always use in town, they said it was nothing in the transmission. error codes saying o2 sensor was bad, so i changed it, that code went away. random misfiring code also went away when I replaced plugs/wires/fuel filter/fuel pump. the problem was still there, but much less pronounced, with check engine light coming on randomly, then off again whenever the hell it felt like it.

It does this every gear, just before shift, much more noticeable in first and second gear, and more often when the motor is hot. it was dealer serviced from the day it was purchased new by the original owner. transmission fluid is clean, as is oil, and the air filters. managed to zip into an auto zone when the light was on this week, got code for the o2 sensor again, and cam shaft position sensor. light has since been off. but the problem persists. it has power when I put the peddle down, no trouble climbing hills, i can bypass the bucking/stutter if i act like im driving a manual, backing off the gas just before shifting, or even giving more gas, its just that sweet spot in the middle that it does it. i can reproduce it by putting transmission in d1/d2

I don't know much about these things yet, and i have talked to some people, all having different opinions, i'd like to find a problem without throwing parts at this van.

other things that I have noticed that may or may not be involved with this problem are: noticeable drop in rpm for a second when going into reverse, no high speed for the heat/ac blower, heat selector doesnt seem to anything, stuck in windsheild defrost i think. rpm seems a little high before it tries to shift out of first (could be normal? never driven an astro before this)

[LiftedAWDAstro]

The defroster not switching is common and is due to a vacuum leak. Look under climate control section for defroster diverter valve.

You mentioned doing plugs and wires, were the cap and rotor also done using only AC Delco parts?

[MountainManJoe]

What was the P code you got?

[1Gary]

Connecting the dots with a defrost not working I agree with Lifted to look for a vacuum leak.As stated it is a common problem with these vans we have read about over the yrs.

[Leconte]

The defroster not switching is common and is due to a vacuum leak. Look under climate control section for defroster diverter valve.

You mentioned doing plugs and wires, were the cap and rotor also done using only AC Delco parts?

Didnt change them myself (which i should have) but according to my bill, cap/rotor were not changed.


codes i got last time, were p0135 and p0341

[LiftedAWDAstro]

If you can, change the cap and rotor with AC Delco parts and then you know they are done. They may not be the problem but they need to be done every 100k anyways. I would also look at getting a code reader like the Actron Autoscanner CP9575. This will allow you to read codes including pending codes as well as some live sensor data like O2 sensors.

[Leconte]

Got the cap/rotor changed, seems to have remedied the problem, though i didnt get to put much road time on it to test it out. but of course, another check engine light came on shorty after finishing. didnt get to scan it, time is tight this week. while pulling the thing aprat , I found a wire plugged into the doghouse on a spade terminal, what is this wire for? the spade terminal rivet is loose and kinda just flaps around. i want to be sure that won't cause a problem for me as well.

[LiftedAWDAstro]

I think that is just a ground for radio interference.

[Leconte]

thanks for the help, the thing is running like a champ now. people can't believe the cap/rotor was causing that problem, they all believe that it would have happened constantly, not only when it was hot.

[LiftedAWDAstro]

It's amazing how many times we see weird running issues fixed with a new cap and rotor. Glad it's running great!