weird idle problems

[RavoHimself]

so a few days ago i started my truck in the morning. usually it goes right into the cold idle circuit and holds the rpms at about 1500 and slowly drops them. when i started it, it reved up like normal but dropped to like 1000 for a few seconds and then held at 1500. but after the rpms would slowly go up and down between maybe 900 - 1150. it only does that when its cold so maybe part of the cold idle circuit? then when i was leaving school the other day i got stoppd at a light which is on a small hill. after about a minute i felt something shaking and turned my radio off and saw my tach was jumping between like 450 and 600. it did the same thing 3 days in a row but only on a hill. i havent tried this when the engine was fully warm but i think its only when the engine is cold. it sounded and felt like it was flooding itself. my engine has 200000 on it and just last week i replaced the muffler with a straight pipe. i dont know if that is coincidental or not. ive recently done a tune up, new plugs, oil, air filter, cleaned the maf. things i havent done are change the o2 sensors (last time i checked they were pretty grimey looking) or the fuel filter. its not throwing any codes. any idea what it could be or ways to try to fix it

 

[RavoHimself]

any ideas

 

[Kroeter]

I had similar things with my 97 ranger. I cleaned the throttle body, which helped a little. But when I replaced the IAC valve..... BINGO problem solved.

 

[flatblack]

That AIC is a real P.I.T.A. You can clean them out and the throttle body is another issue I have noticed on these motors. Could also be the PCV valve.

 

[kryptonitecb]

You can clean the AIC and see if it helps.

Take it off the intake. Spray the carbon off the inside with electrical cleaner. After it has thoroughly dried put it back together and see how she runs.

 

[Kroeter]

Unless the IAC is different on the 93 then it is on my 97. All I did was unplug it, take it off and put the new one on. Not real expensive either.