I recently bought a 95 eclipse Gs AT to give to the girlfriend. I have a 97. I am having a few problems. I work as a auto tech so Ive used good dianostic equipment.The car has a slight mis and no power. It will start then die out when first started in the begining of the day. My 02 bank 1 sensor is reading .08 to .24. Very lean but the weird thing is that stft is pulling fuel around 3%. I have checked the timing, map pressure is around 15psi, fuel pressure is around 45, Good injector pulse, No intake leaks. compression is 180 across. Scanner is reading the ect you can watch it change temp. same thing with the iat. I changed the 02. Vaccum at manifold is 16-17in.The car also has a fresh tune up.
I am starting to lean toward a bad ECU. I was woundering if you guy have any other ideas?

Does the O2 start to cycle after a few minutes of warm-up? I wouldn't be surprised if it was 0.08V-0.24V right at start-up. After a minute, I would expect it to complete 1-2 cycles per second from 0.1V to 0.9V. If it does not cycle through that full range, you may have a problem. Be sure to hook a voltmeter directly to the O2 sensor output and compare that with the O2 output you get from your scanner/logger. If one cycles and the other doesn't, you probably have a bad connection or ECU. With bad input, I'd certainly expect the car to miss and have no power.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire

It only cycles from .08 to .24 at all times. What other conditions would cause the short term fuel to pull fuel when the 02 is reading lean. It should add fuel under a lean condition. Right? Im going to pull it back in the shop this evening.

unplug th o2 sensor and check it directly off the sensor without it being plugged into the ecu. :shrug

Hey bro the O2 only cycling to .24 at a max is of course an issue. You said it's a new O2 though right? If the O2 sensor is new then the issue "should" be something else. When you say the Map is reading 15 psi is that with the car off? The map sensor should see below atmospheric when the car is in vacume. You may want to check the map sensor. The MAP may be dumping fuel while the O2 is leaning the mixture. There are a few things that go into the fueling from the ECU.

You have a bad O2 or a bad connection between the sensor and the ECU.

quick addition here but i noticed your intake pressure was reading 16-17, mine reads 10.3 at start up and 11.5 after warm up? is there a problem with this, i probably should search but i figure theres already a post here so id throw it in, not to steal your post or anything im just wondering if i have a leak or something now. thanks guys
joe

Originally posted by dmt111701
It only cycles from .08 to .24 at all times. What other conditions would cause the short term fuel to pull fuel when the 02 is reading lean. It should add fuel under a lean condition. Right? Im going to pull it back in the shop this evening.

Since the ECU is getting bad input, I would not be surprised if you got funny fuel trims. It may be very confused. Get the O2 cycling and then worry about the fuel trims. When you get back to the shop, hook a voltmeter directly to the O2 sensor output and compare that with the O2 output you get from your scanner/logger. If one cycles and the other doesn't, you have a bad connection or ECU. This happened to my '95 a year ago. The datalogger showed an O2 voltage that drifted in between 0 and 0.1V. A voltmeter on the O2 sensor, right at the ECU, showed a voltage cycling between 0.1 and 0.9V. I cleaned the ECU plug contacts with contact cleaner (of course). That did not fix it, but a new ECU did. After installing the new ECU, the voltmeter essentially matched the datalogger.

Corbin

'95 ESI-T
Now with more power and fewer leaks



Gimme fuel...Gimme fire...Gimme that which I desire

The 15 map pressure is under full throttle it is 5-8 at idle. I did not have much time after work this evening im going to get a reading off the 02 before the ecu tomarrow. I check the wiring today no worn or bad spots. I will let you know what I find out tomarrow.

I forgot to add the the 02 is good. I put it in my 97 and it works great.

Well it's the connection. If that was at idle then your map would be giving incorrect readings. Since that is at full throttle then it is right. check that )2 connection and then go aftere that ECU.

it's official I have a bad ECU!