Group, My '90 Isuzu (4 cyl. manual trans) Trooper has an idle problem. When I shift into neutral, (at a red light) the idle goes up and down from
1000 to 1900 rpms. Up and down, up and down.I just had a new head gasket installed. The shop said I needed a new oxy sensor since the old one was contaminated. They said if I didn't change it the worst would be the check engine light would stay on. I told them to throw it back in there, and haven't seen the check engine light yet. But the rpms sure do oscillate.
What do you guys think. How hard would this be to swap out myself, with minimal time, tools and initiative? where is this puppy located?
Thanks!