Up & down idle 88 Duke when warm

[Fierofool]

Doing some reading on this, if the engine runs rich the oil can be washed from the cylinder walls and the rings will score them.  If it runs lean, overheating is the common issue but you say your engine temp is good.  With the o2 sensor disconnected, there could be damage to the catalytic converter if you still have it installed.  Almost everything I've read says they get better idle and runability with it disconnected.  Common issues created are a slight hesitation at acceleration or a flat spot at a certain rpm.  Lots of people in the Bimmers and Porsches seem to experience bad o2's and disconnect them, or when replacing with a new one start to have runability issues.  Being as it's those cars, they are likely using Bosch replacement parts whether they were owner or dealer installed.   

They say that with the o2 disconnected the ECM reverts to using the base fuel maps and might run a little richer.  When the car is warmed up does the exhaust smell sting your nose or eyes? 

[Donster]

When the car is warmed up does the exhaust smell sting your nose or eyes? 

Can't say it does. We are about to take the car on a 60 mile round trip. I'll sniff when we get back. 

[GTRS Fiero]

Hmmm.  Sniffing a car.

[Raydar]

As I have  not received the new O2 sensor yet, we have been running the car with the sensor disconnected and I must say the engine is running great without.
Doesn't overheat, runs stable, no hunting idle, good mileage, good acceleration.
So, what bad could happen not having the O2 sensor connected?

With the sensor disconnected, the ECM will "plug in" a nominal value. My 4.9 is .445 volts, IIRC. If yours shows .42 volts, then that's what the ECM is plugging in.

Come to think of it, for a long time, "European spec" American cars operated in "open loop" - i.e. without an oxygen sensor - by design. (The ECMs were programmed to run without it.)
This had to do with the unavailability of unleaded gas. The lead would clog up the O2 sensors and the catalysts.
Heck... if it works, run with it.

Odd that it's not setting a code / turning on the light, though. That would lead me to believe there's something wonky with the wiring.

[GTRS Fiero]

IIRC, there was already something wonky with the wiring.  This is a new suspect area.

[Donster]

Wonky wiring or not, for now I am leaving it that way. Need to work on some other things, as this issue has taken up too much of my time already.
Need to get the headliner fixed, A/C, install power windows and the paint job.
If it keeps running the way it does right now, I'm not going to mess with it, albeit it does bother me, as it isn't the way it was meant to be.

[Donster]

When the car is warmed up does the exhaust smell sting your nose or eyes? 

Can't say it does. We are about to take the car on a 60 mile round trip. I'll sniff when we get back. 

No funny smells, however low oil pressure since yesterday. Can’t see how it would be related.

[Fierofool]

Check the pressure with a mechanical gauge before assuming the stock gauge is correct.  Connect the gauge and run it until it reaches operating temperature then check the idle oil pressure. 

[Donster]

I assume its the OPS, not the gauge.
Darn thing is hard to get to, under the TB housing. Plus, the PO installed an 87 OPS. I have an 88 OPS, but can't figure out, how to get the 87 OPS out. Anybody know what size wrench to use on the 87. It is sort of hidden behind the plastic housing that is over the OPS.
Guess I should have removed it while the muffler was out....shame on me.
Thnx,
\D

[Fierofool]

Don, I'm sending you a couple of pictures via email.  I don't have PIP on this computer so I can't post it here.  It will contain pictures of 2 different style senders.

[GTRS Fiero]

The pre-'88 wrench is about 3/8".  I don't have one in front of me.  The '88 will require the oil pressure sender socket.

[TopNotch]

Here are the Fiero Store's pictures of the senders:
85-87


88

[Fierofool]

When I went to Rock Auto and put in 88 Fiero 2.5, I got three senders.  The large old style like the V6's had.  The top one in your post.  The other two were small button-type senders.  One was apparently for a gauge.  The other noted that it was for a warning light.  Did the 88 Duke come with the same sender as the 88 V6? 

[TopNotch]

The 88 duke and the 88 V6 have the same sender.

[GTRS Fiero]

The x84 had a small sender, then there was the '85-'87, then the '88.

Wiring should be in the Feb2019 newsletter.