nocf6

when a 94 lt1 goes into limp mode because of a ses light on a failing optispark or knock sensor what sensors are disabled and what changes when it goes into limp mode.

some sensor apears to have failed while not being used and is now cousing the car to run badly after it i changed the opti and knock sensor and the ses light dissapeard

shbox

I don't think any are disabled. If you had stuff failing, trouble codes would indicate what.

nocf6

i thought at least that the maf sensor was disabled, only codes it comes up with is the opti but i have changed that now twice and everything in the ignition system so i am not listening to codes any more, i know it ran fine in limp mode exept from the slight miss from the opti but now when it is suspose to be fine it isin't

jaycenk

iTrader: (1)

Limp mode is for the automatic transmission. Open and closed loop are the two modes for the engine system. If a sensor drops out to an unacceptable level the pcm is pre set to determine if it will be able to run or not and in which mode open or closed loop usually it is a lot harder to get it to go into open loop with just one senor out of range. it usually needs it to be non registering meaning like it not plugged in or multiple sensors out of range. One way to test if it's a problem in closed loop is to disconnect the MAF and see if it runs better. This forces the PCM to run in open loop. You might want to list specifics as to what you have already done and what the codes are and where before you started swapping parts. This will help people on the site understand better what might be going on with your car. Also list some basics about the car. 94, LT1, What transmission? Is the engine stock? Do you have any boltons? Is everything else stock or has anything been rebuilt? What brand opti did you install? Did you change the Opti harness? What knock sensor did you install? Was it for the correct year?

nocf6

it is a 94firebird formula with a t56
it had a code for opti and knock sensor when i bought it and was missing a bit, but ran fine, both fans were always on so it never got hoter than 210°.
I changed the opti (not sure what brand) and knock sensor, first got for the wrong year,then got the right one. After that ses light went away and now it heats up normaly, fans come on at the right time. but if i turn it of while hoter than 210° it barely turnes the engine over once and it wont start. also if i let it run for a while after having reached 210° it starts backfireing badly at 3000rpm and wont rev higher that then at 2500 then 2000 and so on until it dies

it somtimes did show a ses light so i had a shop scan for codes and it came up with a code for the opti, the shop was guesing that the opti i got was bad, so i changed that again but no difference

i tryed unpluging the maf and let it run like that and it ran just like the day i got it exept no missing from a failing opti. and of course never got hoter than 200°

now i am thinking does it run fine with the maf unpluged, because the maf is failing or because it never reaches the temperature it was failing at with it plugged in

sorry about the bad english