engine mis firing at idle

[bradical]

anyone familiar with the 2.9L 88 ranger v-6? its got 220000k on it. when i start it lately it doesnt run smooth, like it is skipping. it does ok once you are driving it. doesnt seem to matter hot or cold start. replaced the O2 sensor yesterday, that didnt cure it. has relatilvely new(1 yr old)plugs and even newer wires. any suggestions would be helpful. check engine light is not on. not many machanics want to deal with something this old. thanks in advance, brad

 

[dgndngrngr]

unfortunately too familiar haha
rpm surging?
could be the timing
but probably the throttle position sensor (its on the left side of the throttle body) looks likes this: http://www.autozone.com/R,1416058/vehicleId,1127502/initialAction,partProductDetail/store,2258/partType,00136/shopping/partProductDetail.htm

i think

 

[ruppy22000]

Change the plugs. I have had plugs crap out on me in 3 months, time doesn't matter with them (in my truck anyway).

 

[bradical]

throttle pos sensor. ive heard this term before. i have no idea what it does, but it looks like an inexpensive treatment. every now and then, now less frequent than before, ill adjust the idle screw on the TPS bc it will occasionally want to knock off at idle. someone told me not too long ago not to be doing that. the exhaust also gets too smelling a bit different, not full time though. it has a slow oil/coolant leak at the front of the engine, to the tune of about 1 qt every 1000-1500 miles. i plan to fix that in the near fututre. its "only" got 220000 on it like i said, so i feel that ive been fortunite.
i may try the plug thing too, i had to replace the wires not too far back b/c it was definately missing at highway speed, so i got to pulling wires off with it running, and isolated the one that didnt make it run different then replaced it temporarily, then the whole set.

thanks for your advice, any further will be appreciated as well

 

[dgndngrngr]

does it sound like the lifters (quick ticking) or do the rpms fluctuate at idle? could be a bad plug like ruppy said

if you pull the plugs check the compression on each cylinder with a compression tester. it gives you a pretty good idea off whats going on with your engine. if one cylinder shows 20% less compression than the rest id suspect a cracked head near that cylinder.
some other signs of a cracked head or blown head gasket are coolant smell in the exhaust, "snot" under oil cap after driving a while, milky or sudsy looking oil.

and with 220k on it and no major problems yet sounds like someone actually took care of their truck! it would probably go another 100k even if you didnt fix anything

 

[bradical]

well thank you. it is my first car, bought it used in 93. i have babied it, but at the same time used it like a dumb teenage redneck boy does. anyway, i got to work today, stared pulling wires, and the same plug isnt firing again. gonna get on that first thing in the morning. thanks for the help guys. will try to check back later.