my father has a 95 jimmy, and as of late, it has been idling very strangely, (surging, stumbling and running VERY rich) he replaced the TPS today, and it just made it worse.

I know NOTHING about these motors aside from what i read in his haynes manual. I was thinking it was the cam or crank position sensor, or perhaps an injector that's sticking open.

it will occasionally miss while running. i haven't driven it since this started happening, but i did hear (and smell) it idle.

any insight would be greatly appreciated.

is it showing a service engine light? sounds like the egr to me.

OK,
I had a similiar problem with my truck, an 88 with a 350 tbi, i replaced the O2 sensor that fixed my run rich, the MAP sensor helped the idle subsantially and finally the knock sensor helped the pinging and miss fire go away, also inspect all your wires and plugs, wires that have arced are also a big problem. I figure we have the same sort of electronics and those things i just listed are quite common things that cause what you are decribing, As for the order i would do them it it would be the wire and plugs then the O2 then the knock and then the map. But try the wires ,plugs, and O2 it doesnt take all that much to have an engine run shitty.
Hope you get your engine running, :)
Dave

P.S. Keep me updated on what it was!

Two of the most common things to check on the engines are the EGR and IAC. The egr passages clog up with carbon, and the IAC will seize up throwing of the airflow in the throttle body.

Check fuel press,plugs wires and everything like that, fuel psi should be around 50 psi if it is any less the engine will not run due to lack of fuel press. The spider injector will not open poppet valves as quickly or effieciently. Hope some of that helps.


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