SES, code 13, running bad

[patgizz]

my 94 euro set the SES light the other day. i was driving on the highway going 70 with the cruise set. it came on for about 30 seconds then went off. i drove another 30 minutes home and didnt set it again. i used my little actron scanner and pulled a code 13 which is listed as: Oxygen sensor voltage stays between 0.35 and 0.55 volts for 25 seconds. The engine had been running for at least 2 minutes and the TPS was above 4%.

i took it out last night to see what was up and it was very sluggish below 3000rpm and not its usual neck breaker from there on up to 6500. also the idle is a little weak and when put in gear it tries to stall.

for all purposes pretend its a 91 cutlass supreme cause that is what my drivetrain/ecm is fromwhat does the low voltage for the o2 sensor mean? i think my book that came with the code scanner said it was running lean. does this point to a bad sensor or am i looking at some other possibilities?

it feels kinda like my van that has a bad fuel pump but unfortunately my pressure tester isnt here right now and its broken as well.

[93LuminaZ34va]

USUALLY..... its a bad sensor. However, I would check the fuel pump first before I buy a o2 sensor. 9 times out of 10 though, its the sensor. How long has that sensor been in there? What kind is it, if you replaced it?

[patgizz]

its the original one off my 94 3.1 so its got 136k on it now(put it on the 3.4 cause i broke off the 3.4 one pulling it out of the donor and i ran out of $ during the swap cause i ran my cooling fans over with my truck).

ive got many a stock one laying around but i'll go buy a new one this time.

[93LuminaZ34va]

Definitely sounds more like a sensor to me. You did DAMN good getting one to last that long.... the one in my Z34 is gonna get replaced, but she's made 110,000 miles.

[patgizz]

checked the voltage and its spot on from the computer. new bosch o2 sensor. no change, still running bad. it almost feels like its got a slight miss in gear idling. it definitely does not sound right. i got my fuel pressure gauge back the other day so i need to take it in to have replaced, then i can test that. i know how tempermental mpfi systems are to low pressure so that might be it. i do not want to drop the tank but if it needs done then it needs done.

[jmgtp]

An easy check (that is if my understanding of how/when the ecm uses the o2 signal is correct) to see if the o2 sensor was the problem would be to just floor it. As far as I know the ecm disregards all o2 sensor input under WOT. If it ran normally at WOT then the problem would point to the o2 sensor. If it still ran poorly, look elsewhere. Maybe you will luck out and its just a severely clogged fuel filter.