89 GT-S odd raving during start up

I have 8o GT-S 3sge, with 101k miles, in V.GOOD shape inside and out, but the old lady who owned it her brother said it had this problem that rarely happened, and one day it happened to me. It's like a strange revving of the engine from maybe 750-2500 aprox. It has only happened once, I just opened the throttle a few times and it stopped the fluctuations. But I'm stumped. It has entered happened again yet but I want to find this problem before it comes back on the regular. If any has any good ideas. I figure it could by something with the fuel pump, I know this engine has a odd design with the full line running through the crankcase. But idk. Lmk huh.

 

Not 8o. 89' GT-S

 

No its unstable it's revving between about 750-2500, up then down, the I step on the gas and it stopped. Like an up and down idle as if we're almost about to stall but then catches and the rpms increase to 2500, about, then drop back down low.

 

Well I changed the air filter and I don't see any VISIBLE damaged or messed up Vac hoses. But I did slap some Lucas fuel additive and oil treatment/ stanilizer in her and took it down the interstate and opened it up wot, haven't heard anything yet. But the guy who's Sister owned it before said she only noticed it happen rarely. It was her to work and church car and it the city that means slow speed and short distances. So idfk. We shall see. But it seems like when I put the over drive on it shifts funny at highway speeds. I just had the transmission serviced by a specialist shop and the said there was no hot points. So idfk. Not slips or lags in shifting just it seems odd.

 

No cracks or anything, the sputtering happened again yesterday that the 2nd time since I bought it is February. But this time it seemed less intense. But I'm going to seafoam the shit out of the throttle body and go from there.

 

I have and it seems tip top man. BUT I'll check again. But it is a sporadic thing. And only during rare startups. The guys I got if from told me about it I figured it was a fuel problem, or that the fact its 28 yo.

 

So I asked around and some guy says there's a hose that feeds violent to the throttle body little hose on the very underside he claims it gets closed with silicone and can cause uneven idle. I haven't checked since it hasent happened this summer.

 

So my biggest worry now is a wayward head light that works on it's own time. So.e times it comes up and sometimes it don't. The light is on but it won't raise. Then one night is will. Getting me right pissed that thing.

 

Is this a hint? :/

 

Yeah it's just shot needs new motor or at least a re-man for the headlight. But I haven't had an issue since end of March so who knows maybe it is a cold start injectors. I don't think it's fuel pressure. Or timing I pray. But come September I'm takin it in for a complete tune.