I have a 98 4.3 v6 when i first start it in the morning it gallops and serges, then in awhile it straitens up some. still serges while driving it some, when its first started the exaust is very rich. it starts good. engine light is on.

I can't remember tha name of it but my friend had same problem. Usual worse on a hot sunny day. It's nick named tha shade tree sensor. He could drive to work on morning but got off an it wouldn't start to go home. Il ask him what it was called an get back to u if u like. But was same car same problem

Dead Battery or Starter

You saw that coming or the shop you go to
let you down

plays what?

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It isn't over heating correct? When it starts acting up, what exactly is happening? Any engine light coming on?

Probably the oil filter is blocked.
Warm it all up with a 30-45 minute drive & then change the oil in the gearbox whilst it's still hot. Make sure you also change or thoroughly clean the gearbox oil filter at the same time.
After that you're looking at the tension bands & the dog-clutches, which are a specialist mechanics job.

Likely leaking past the front pump seal.Drain fluid,replace with synthetic fluid and add a seal conditioner with it

I would replace the low pressure AC compressor cycling switch, it may be sticking, it is a fairly common problem. The switch is located in the low side of the AC system hoses or accumulator.

sounds like an engine management fault it will need to go on a computer

defective starter

What does it smell like? If it smells like rotten eggs that is a tell-tale sign that your catalytic convertor is bad.