what are the symptoms of one going bad? i have a rough idle when cold (runs like it has a big cam) also have a slight hesitation after warm up when starting off at lights.going down the road runs normal,thanks for the help.oh its a 91 t/a 305 tpi. new tps,map, sensors.unhooked coolant temp sensor,ran worse,hooked it back runs better, jimmy

 

run it with the aldl jumpered and check if it falls out of closed loop, a slow flashing CEL = closed loop (flash = crosscount), fast = open loop (probing for V signal)

 

thanks man ill try this and see, uncle has a scanner but havent had time to get it , maybe wed.i have long tube headers on it too thats why im running a heated sensor. i just didnt know what it did when it starts to go bad ( its used anyway ) so i have a feeling this may be the culprit,thanks for the reply ,jimmy

 

To check O2 use scanner it should see about 5 cross counts, pull brake booster vac line and watch to make sure it goes lean 2v then spray some carb cleaner to make it go rich .75-.8v. This is a rough test but if it doesn’t do the full sweep then its bad. Make sure its hot! With motor running at 2000rmp it should switch from rich to lean pretty quick. Check TPS and make sure it is adjusted to .56v if its adjustable, with engine of watch volt meter or scan tool and watch voltage to make sure it does not “jump” as you slowly open throttle. TPS is a common cause for hesitation off idle. Is rough running only a one cylinder misfire or is entire motor running bad?

 

At what temp?
O2 sensor only works when in closed loop which is determined by engine temp amounst other things ; so while warming up a bad O2 would not be a factor because it is not being used

 

thanks for the replies fellas ill see if i can get the scanner ,ill hookup volt meter tomorrow. it really runs rough when warming up so may be its not o2. payed more attention to it tonight coming home kinda acts like bad tps.again thanks,jimmy

 

did you run it with the aldl jumpered? no need for a scanner, just a paperclip

 

no not yet may try it tomorrow just got of work havent had time may do it later tonight,jimmy

 

ok got the codes .22-24-34-44,jimmy

 

One more and you would have hit the jackpot
Looking like a TPS problem

http://www.troublecodes.net/GM/90-91_50F.shtml

 

unhooked battery cleared codes (most were set by me unplugging sensors to see what effect they would have) replaced coolant temp sensor runs a lot better still a little rich though,jimmy

 

oxygen sensor is working, 1 down, new coolant temp sensor,2 down, tps is working (according to meter)3 down? anyone have a working used one they want to sell so i dont waste a lot of money? it runs kinda good after warm up,but if i press throttle enough to go to 2,000 rpm it stumbles all over itself for like 4-5 seconds revs up runs right ,let off press it again revs right up. i think its the tps but not sure. what do you guys think,thanks for all the replies,jimmy