About a week ago I took a long drive and my car started acting crazy. I would have to gun the gas for it to move and all it wanted to do is stall out. It now does this most of the time unless the car is fully warmed up. If the temperature guage is a dot below where it should be the car acts crazy and the RPM is very unsteady. But once it hits the point where its fully warmed up it runs perfect. So far I have changed the temperature sensor and throttle position sensor and its still the same. I also noticed other weird things like if the car isnt fully warmed up and I drive it, it actually gets colder as im trying to keep it from stalling. The gas meter also jumped from a half a tank to empty back to a 1/4 if this has anything to do with it. My car is a 89 SE automatic. I would appreciate any possible help. Thanks

 

It might be your O2 sensor, which is attached to the passenger side of your y-pipe. You see when the engine is cold the O2 sensor runs in open loop and once its warmed up it goes into closed loop (I might have the open/close thing backwards). Maybe the sensor is malfunctioning or not reading when the engine is cold. I'm not totally sure if this is your problem, but if I had this problem, the O2 sensor would probably be the first thing I'd check.

Goodluck,
Kevin

 

lessee. If I recall right, the engine ignores the o2 sensor while it's cold 'open loop'. Once the o2 sensor warms to a specific temperature (400F?). It begins to generate a signal, which is then used by the ECU for 'closed loop' operation. Hopefully someone who knows their stuff will fill in the gaps. I know for a fact my o2 sensor is going, and I have a lot of similar problems.

While cold, if I lightly press the gas, the tach actually drops 100 or so before inreasing. While warm, the engine misses and surges while running overly rich, especially at idle.

 

Hmm car's engine temp gets colder is a clue I think. It sounds like a thermostat not working properly(ie.. stuck/opening at the wrong time etc)

The car stalling out when cold sounds like it's running a closed loop a/f(leaner) when the car is actually needs an open loop program(richer). Is there alot of black smoke? Or is it just normal white-ish color exhaust?

 

when cold the ecu does NOT pick up a signal from the O2...so you're wrong in that part.
but u got the open and close loop right...but didn't understand the concept.

 

I'm going to try to change the O2 sensor next. The smoke from the exhaust is a normal white-ish color. Thanks for everyones help. I'll post back after sensor is changed.

 

if it runs right when it's warm..then i wouldn't change it unless you know it's bad..or if it's been on the car for a while.
don't just change a part for the he11 of it in hopes to fix it. find out the problem 1st.

 

I tried to post this last night but the .org was hosed up like always.
Mine failed most of the tests.

http://www.mr2.com/TEXT/O2_Sensor.html

 

If your car gets colder as you try to drive it, maybe the thermostat has been removed? It's common to take the thermostat out entirely during the summer, but if you leave it out as the weather gets colder the engine will not warm-up properly. Does your car take a long time to warm up? It sounds like the problem definitely has something to do with open-loop mode, in which your engine runs on a preset program from the ECU without adjusting ignition timing or fuel/air mixture. Perhaps the ECU has an open-loop glitch. I have to opposite problem on my '94 SE DOHC, it runs great cold and then gets sluggish when the motor hits closed loop mode. good luck

 

I just wanted to let everyone know, I changed the O2 sensor and so far the car is running perfect. Seems like the O2 sensor did have something to do with the car when it was cold. Thanks for everyones help.

 

Exactly like I said...I'm happy to here that your car is running stong again. I myself replace the O2 sensor on my '90 GXE just for the hell of it. My girlfriends parent own a business exporting auto parts, so I got a brand new NTK free of charge. One thing I noticed is that the car seems to have gained some lost power. Its to early to tell, but I think my gas mileage is better. And on my way home from work tonight I was stopped at a light all by myself with the windows down and I swear I couldn't even hear the engine running.

People on here always say not to replace the O2 unless you have a severe loss in gas mileage or power, etc. But damn!! Certain electrical parts can only last sooooo long!! Especially the harsh conditions the O2 sensor is under. I think Bosch even recommend changing the O2 ever 3 years or so.

Later

 

i spent about 100 bucks before getting a new O2 sensor but i got one for 60 bucks.."STANDARD" is this brand any good?... i think the sensor is getting bad again,

if your car is running a rich fuel mixture for about 4-5 hours this will kill the O2 sensor, becasue all that fuel/carbon gets on it and damages it...


just some facts