'99 Firebird - jerks from 1st to 2nd

Car is an automatic, 3.8 V6. After a trip of 170miles or so whenever going from 1st to 2nd there is quite a 'jerk', and a smaller one from 2nd to 3rd. I've found I can make this stop by taking the gas cap off for about
15 seconds or so then everything is fine. Another problem I've noticed is that sometimes up until about 65mph the car will run rough or hesitate, above that it seems to run fine. I don't notice any drop in rpms though. The converter was just replaced last year, the car has a bit over 84k on it. Any ideas on what to check?
Thanks Chris
--
Chris RLU 283774 Mandriva 10.1 Official
20:26:05 up 3 days, 14:16, 1 user, load average: 0.55, 0.45, 0.30
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Is it just a 'jerk' or 'surge' forward or is there a 'thunk' noise included?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
dle wrote:

I'd have to say it's just a 'jerk', enough to throw you forward in the seat. I might add that this is the same 'jerk' I got one day when I had to make a trip from my house to Austin, Tx and on the way back not only did it 'jerk' but the 'check engine light' came on. Got home and found that when I had gotten gas that morning I'd neglected to tighten the gas cap. After I'd tightned it everything was fine. Now that I think of it, the 'hesitation' I'm getting is actually a light 'jerk'. Could the gas cap be bad?
--
Chris RLU 283774 Mandriva 10.1 Official
09:06:11 up 4 days, 2:56, 1 user, load average: 0.23, 0.23, 0.13
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
That could be a possibility I imagine. One thing I would do is either scan your car to see exactly what the code you are throwing is. If you don't have a scanner, go to an AutoZone (if they have one out there, they do out here in CA) or another autoparts store the will allow you to borrow an OBDII (or is your car OBDI?) hand scanner. See what the code is that your are throwing. If the 'check engine light' isn't on anymore, you might try to see if the scanner they have includes 'freeze data'. This should also pull codes that have 'cleared the light' but are still in the PCM. That should also be able to give you a lot of different data about the car at the time the code was thrown.
You might be having MAF problems or an O2 sensor has gone out. A code scan would tell you also if you are having any misfires. But that is where I would start, get a scan and find out what code you are throwing.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
dle wrote:

Got an AutoZone just down the street. Thanks for the help, I'll give that a try. The 'check engine light' went off after I tightned the gas cap, hasn't been on since.
Appreciate the help
--
Chris RLU 283774 Mandriva 10.1 Official
12:54:28 up 4 days, 6:45, 1 user, load average: 0.16, 0.11, 0.09
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.