86 2M4 stock 2.5L 4 cylinder w/ automatic

O2 sensor does the normal rich/lean readings as a response to computer control of the injector.


A/F gauge

If the car idles at a stoplight, the sensor readings slowly go lean to very lean, rpms drop & engine will die.

Also after cruising for about 80 miles at 60-65 mph, the sensor goes lean when going up grades or slight increases in elevations. It will stay lean long enough to trigger the SES light with code 44. I can either floor the gas or hold the cruise switch over to the right, causing the engine to go rich. This will turn off the SES light and the O2 sensor resumes the normal rich/lean reading until the next rise.

During the next rise when the sensor goes lean and before the SES light is triggered again, I can decrease the cruise speed 1mph by momentarly pressing the cruise button in the end of the stalk. This causes the O2 sensor to temporarly resume it's normal readings.

If the A/C is on, it makes the engine more sensitive to load increases such as hills.

Lastly, coming into a 30 mph zone, I let the car coast down. This also causes a very lean situation triggering the SES light. Boot the gas to turn off the light and O2 goes back to normal readings.

Question: Is this an O2 sensor problem? or A computer problem? or Something else?

[This message has been edited by 30+mpg (edited 08-05-2006).]

any way to get winaldl plugged in to see what the computer thinks the TPS is doing?
i think 86 was the last year you could use winaldl on the duke.

I have an Auto Xray Scan tool I can plug in & check the TPS readings.

BTW I noticed the problem on the way back from KCMO this morning.

[This message has been edited by 30+mpg (edited 08-05-2006).]

If that meter is sharing the main O2 sensor... Disconnect your dash meter. The O2 sensor isn't really meant to run more than one thing. The load from your meter could be skewing the reading the ECM gets.

Beyond that, start looking for Vacuum leaks. Even small leaks are unacceptable. Next check fuel pressure. You could have a fuel pump or TBI problem.

Chruise is great for leaking vacuum but any part of the vac lines etc with a small leak can make the engine go lean. You don't want to keep running like that or you could damage the engine.

TPS shows the computer 0.80 volts at no pedal through a steady progression to 3.62 volts at WOT.

Might this be the problem?

Any RTV I've used on the engine reads "Oxygen sensor safe" on the squeeze tube.

I'll swap it for a good one and see if the problem goes away.

Any way to clean the O2 sensor?

Yes, but you need to replace it. It can technically be cleaned but no one can afford the cost or process.

I have heard that you can use tip cleaners that are used in cutting/welding to clean an O2 sensor - never tried it...but then I also have nevered used RTV on the sensor (maybe I should??)

Tim

The only places I use RTV on a 2.5L are oil pan, timing cover, water pump, valve cover, lifter cover & themostat base.

quote Originally posted by 30+mpg: How much heat can the ECM take?

Not sure they have that in any text--if this helps, ex: the Park-Ave-Ultra & other Gm vehicles with 3800SC in them , stick the pcm in the same path as the air box---under the hood..

Switched O2 sensors. Drove 52 miles to Joplin airport on Wed. Last 10 miles, same problem w/ sensor indicating too lean, Code 44 when encountering a load increase.

Drove back from the airport today. Ambient air temperature was about 10 degrees cooler. No problems w/ mixture going lean. Coolant gage indicated same temp in both situations.

[This message has been edited by 30+mpg (edited 08-11-2006).]

I'm chasing down a lean condition on my 85 duke (glowing exhaust, melted throttle cable) which crept up on me. I hve no problems with acceleration (except that it's a Duke, heh) or change in top speed (whatever traffic allows) except that the car takes a while to start. I changed the fuel filter a month after the 10% ethanol switchover because that's whenthe problem strated, and I'm getting NO codes. Car idles at normal speed, even with the AC on.

Anyone else care to suggest a fix? I've had no problems for nearly a year since I got the car on the road, with a lot of repairs prior to that, and I am getting NO CODES. see my posts in this now-archived thread for more details

Well, not sure if this would help, but;

I went and got a little over the wall and picked up an oxygen sensor from a 92 Cadillac Deville. The two-wire one. One is a signal, the other is an additional ground. Splice on the fiero connector to the signal wire, wire up the other one to a good, solid VERY CLEAN ground. Great O2 response now. The exhaust needs to be well grounded to get a good clean signal to the ECM. This helped out alot on crappy idle problems for me.

Just my two cents. BTW - cheap sensor, like 20 bucks or so. Well worth it.

quote Originally posted by Shibbypoopalot: The exhaust needs to be well grounded to get a good clean signal to the ECM.

I think you may be onto something here.

Still goes lean to open loop after about 40 minutes of driving. New O2, TPS & MAP sensors. Also goes lean when A/C is on after about 30 minutes of driving at 65 mph. Switch A/C off, O2 reading goes back to normal, fluctuating and ECM maintains closed loop.

IAC checks out OK.

[This message has been edited by 30+mpg (edited 09-16-2006).]

Can you scan it and tell us what the BLM is when it's in closed loop?

Auto X-ray Data: (Cruisin' in town w/ A/C on.)
Idle air motor 63 steps
Coolant temp 203.6 F
Speed 31mph
MAP 1.64 volts
RPM 1400
Throttle sensor 0.94 volts
Integrator 128
O2 sensor 0 mVolts
Battery 13.2 volts
Block lean 160
Cross counts 164
Voltage High No
Clear Flood Mode Off
Learn Control Enabled
Voltage low No
Rich Lean Flag Lean
Loop Status Open
A/C Requested
Engine Cranking No
Park/Neutral Not Detected
TCC Status Locked
A/C Clutch Enabled

bumper

it is recommended to replace the O2 sensor yearly. if you dont remember when yours was last replaced - do it.
and, if it is new, the next problem may be a real one: bad/clogged injector.

Hmmm,I do remember that I just recently replaced the O2 sensor with a new one.

Maybe a lazy throttle body injector?

[This message has been edited by 30+mpg (edited 10-12-2006).]

We had a Fiero come in with hard starting and driveability problems. Scan tool showed the Block Learn was maxed out (160) and it was still lean. Changed the fuel filter and it was back to normal.

quote Originally posted by 30+mpg: Hmmm,I do remember that I just recently replaced the O2 sensor with a new one. Maybe a lazy throttle body injector?

well, I just looked at your "auto x-ray data" and see you O2 reading is 0 (zero)
the wire or connector might be burnt thru
makes it hard to beleive your A/F meter does anything

It may be because its still showing him to be in open loop, but even with just the key on and no engine started you should have a reading back to your auto x ray data. Your block learn mode is high.

O2 signal is good when it ECM is in closed loop. Read my prior posts carefully.

Fuel filter checks Ok, good flow.

[This message has been edited by 30+mpg (edited 10-13-2006).]