I noticed on my scan- when I'm at low throt. 4- 6 % the mv will go down to the 50's and stay there for around 20 sec... then when I get back on the gas the sensor ' wakes up' and acts more normally crossing 500mv up and down. One other thing on the scan shows the mv around the 50's for 6 or 7 sec., then 645 for 1/2 sec, then back down to the 50's for awhile. Is it time for a new sensor, perhaps?

 

Sounds like it's gone "lazy" and it's probably time for a new one. If the car's in closed loop it should be changing VERY quickly...

 

Are you running headers?.
The O2 has to be HOT to function.
If you're not running a heated O2, and headers, that might be your problem.

And, yes, they do get old, and lazy.

 

sorry to jump in but since your on the subject of o2 sensor replacement anyone have any tips for removal i have an o2 socket thats cut down the middle for the plug but it stretches too much and the o2 wont budge?? thanks

 

Justlearning, is that a socket you bought, or did you make it?
Grumpy, no I don't have headers, and the car was hot in the scan. Guess I'll go get a new O2.. Thanks for the replies.

 

bought at auto parts store for about six bucks

 

I have one that I bought for about 30.00 CAD and it never flexes... might try some WD-40 or something.....

 

Ill third what they have siad, it sounds like it is dieing or gone already

If u are replacing it, let the car cool off and soak it with some type of penetrating oil.

If that fails, u can try heating the manifold up and then trying to bget the sensor out. Warning here, be careful if u are forced to go this route you can tear up the threads in the manifold. shouldnt be too much of an issue on cast stuff though, least I never had any

Once u break it free take it out and clean the manifold up with some carb spray or brake clean so u dont get oil all over the fresh sensor.

later
Jeremy

 

ok new sensor, problem still persists. Today it got stuck at 13mv for about 6 sec. It gets stuck at low values anywhee from 4 to 50 mv. What else could it be? btw the car is hot and in closed loop when this happens, no headers.

 

Sounds like DFCO to me, maybe a normal occurrence. . .

RBob.

 

RBob, thanks for the reply, I have DFCO disabled, however - until I figure out how to make it work properly.

 

mine's doing the same thing. 4.44 mv for a few seconds - which quickly makes the blms rise. Going to try an AC Delco o2 sensor this weeked

 

Is this the '88 with the '165 ECM? Mask? The reason I ask is that I know with the $8D code there is a minimum allowed PW. Once the PW goes below that value the injectors are shut off. This can happen under very light load at medium engine speeds (above idle at least).

What is happening PW wise when the O2 drops? Are you running the stock injectors and fuel pressure?

RBob.

 

RBob, yes I'm running '165 , $6E , ARAP with ford 19 # inj's. Stock FPR . The inj PW doesn't seem to do anything strange when this happens, acts as it normally would with throttle input. Matter of fact, the BLM's don't seem to do anything strange at the time, either.

 

Could it be that I need a heated O2? I have stock manifolds, but no cat, and Hooker catback. I thought I only needed a heated O2 if I had headers....

 

with my reading here - everybody praises the AC Delco 02 sensors while saying the others exhibit the problems we are both having. Stock manifolds should be plenty hot to get your 02 sensor to work properly.

 

OK just one more development on my last scan of the evening... I noticed that the O2 only locks up at really low, constant throttle - around 4.7 % or less, and when I either jab the trrottle, or let it off, the O2 returns to normal, swinging up and down.

 

What are the pulse width and BLM's doing when this happens? Any oher sensors jumoing around at the same time?

 

Colder weather and climates can indeed even cool of a delco non heated 02 to where the car can go into open loop even with stock manifolds.

I have seen it on my GTA and my Formula when stock.

This is on colder days and prolonged idling is when I found it most often.


Just noticed that he is in BC and its late in the year

later
Jeremy

 

For example, an occasion where O2 drops slowly from 9 to get stuck on 4 for 8 seconds, BLM stays at 128, BPW varies from 1.65 - 1.94. No other values are doing anything strange at all. Could the prob. still be a cold O2 even though as soon as I change throttle position - + or - the O2 returns to normal ?

 

Is it entering into highway mode when this is happening? Look at the desired AFR in the datalog and/or if the BLM learn bit is marked as active during the event.

 

AFR during the event is 14.71 in the datalog, and not in hwy mode, happens at any speed, only at low throttle position, usually about 1.8-2.8 %. As soon as I change the throttle up or down, O2 acts normally. Has NO effect on blm's at all.