Hello, I am new to this board.

I have a 98 Riviera s/c 145k miles, I bought at 78k miles.
It's a beautiful car still, and I love it, I just have a slight (hopefully) problem i'd like to get cleard up.
A while ago, it started stumbling/missing when given slight throttle at about 45mph, it would go away when given more throttle. It then started doing this off idle, when first started in the morning (cold), and would clear up quickly.

My first instinct was Tranny problems. I brought to mech. and he checked for codes and drove it, said tranny was fine, no codes. He thought the motor was missing at that particular shift point/rpm combo for various reasons. We tried new fuel filter, and both o2 sensors. It seemed better for a while, and is now back to acting the same. I put new plugs in about 6 months ago.

Service Engine light IS ON. Mech flashed it off, and it came back on about 2 weeks later.

Mileage has gone down about 10% over the past 6+ months.

Any info to help would be appreciated...I'd really like to not have to chase this problem forever, and keep throwing $ at it.

Thanks
Greg

what code does it show? have you cleaned the intake with sea foam yet? and you are running prem gas right?

I don't have a code for the Service Engine light.
No, I have not cleaned the intake with Seafoam...I haven't heard of that before.
Yes to the Premium gas.

Thanks
G

here is a great resource, it was a co-op site created by a fellow riv owner,myself, and some other members. it has instructions on how to clean the top end of a GM car. the sea foam can be found at autozone,advance,napa,etc. it is wonderful stuff. i do my car about once every 2 years or 15k miles. you may want to clean up the MAF and throttle body while your doing some maint., if they look bad.
http://rivfaq.freespaces.com/
btw the gm top clean procedure says to use the special gm stuff (and you can) but sea foam is a little bit cheaper and the same exact thing (pure petrol) and the tube they say to get is also used as air lines in fish tanks ;)
if you have any more Q's please post them, and if you can get autozone to scan for any codes that could also help. (they do it for free)
matthew