Here are all of the symptoms:

Car runs fine but gas mileage is low. Will throw a code 44 once in a while.
Mc Solenoid dwell:

cold start constant 20's open loop
closed loop seems to hover at 30 ish then very shortly goes to 2.9. Very short time at 30......less than a minute.

Changed O2 and temp sensor. O2 seems to be throwing between .4 and .7 volts. When a hook a 1.5 volt battery (positive) to the O2 wire back to the computer and the negative to ground, the dwell rises to above 30. This would indicate a bad O2 but the O2 is new and putting out the correct voltage.

If I blip the throttle the dwell will momentarily increase to 15 to 20's and then immediately back to 2.9 even when revving the engine.

The carb is rebuilt and there are no air leaks. It did the same thing with the original carb so I replaced the carb, O2 and temp sensor. Car seems to idle smooth with the mixture screws out 4 turns. The IAB on top seems to have no effect (I have not cranked it in or out but merely a half turn either way.

I guess I am saying it is not the carb, O2, or temp sensor...Or what am I missing?? I hate to replace the ECM if that is not the problem. No other codes.

Thanks for any advice.

 

My 85 LG4 did that. I changed the O2 also and it actually turned out to be the wire going from the 02 to the ECM. Check your 02 output reading right as it comes out of the sensor. If it is good there then check the reading right at the wire as it goes into the ECM. If the readings are inconsitent you have a bad wire. You will have to skin the wire back a little in both places to take the readings.

Do you have a scan tool at all?

 

many idle air bleeds aren't adjustable, the ones that are will only make very small changes unless you go too far.

to set the idle mixture, you must use the dwell reading.
the best idle isn't what the ECM wants. the ECM wants ~14.7 AFR.
best idle on a stock motor is ~15.2 AFR.

with the key on engine off, O2 sensor unplugged, check the voltage at the ECM side O2 sensor connector. it should be ~0.450. if its close, check the AIR injection system.
the AIR system should only inject air into the exhaust manifolds for a short time when you first start the motor when cold.
its pretty common for the AIR injection valves to start leaking after a few years.
if most of the AIR system has been removed but it still has the check valves and they aren't capped, they will pull fresh into the manifolds
any air leaks into the exhaust will cause the ECM to think the motor is running lean and the ECM will try to richen the motor up.

 

I will check out the air system...thanks. As for the O2 sensor, how can the wire be bad if when I connect a 1.5 V battery to the ecm side I get a change in dwell? And the voltage from the new O@ sensor reads at about 0.5V. I made a better connection (made a jumper) between the O2 and the ecm wire and there was no change in dwell at all. However, I will check. I do not have a scan tool.

 

A rebuilt carb is going to need to be adjusted to your motor. After you've ensured that the TPS is good and reading near 0.40-0.50 volts at idle (and all plugs/wires/cap/rotor are new), set your idle mixture screws at 4 turns out. With the motor warmed up, start at 2.5 turns out on the IAB and turn it out 1/8 turn at a time waiting about 20 seconds between each turn. You want the dwell meter to start wavering as it adjusts for changing O2 readings. Once it's wavering back and forth, maybe +/- 10 degrees, adjust the IAB so that it's nearest 50% (or 30 degrees on the six cylinder scale) at idle.

Don't go more than seven turns out on the IAB. If you don't hit the sweet spot somewhere in there you may need to start with the idle mixture screws in 2.5 turns out and repeat the above process going another 1/2 turn out on the idle mixture screws after each iteration. You want to end up somewhere near 4 turns out on each.

Make sure the idle mixture screws are at the same number of turns out.

I like to plug all of the vacuum ports before proceeding, get a good dwell then re-install each one. If one is leaking the change in dwell will show it right away.

Make sure the dwell is wavering. The dwell will change with throttle position and VAC reading even if it's not receiving feedback from the O2 but it will be an even change. You want to see it bouncing back and forth in response to the O2 lean/rich flag.

Code 44 doesn't necessarily mean the O2 is bad. Your mixture is most likely JUST lean. Try the above and check for vacuum leaks.

 

New info. The car reads about 30 to 33 dwell in open loop. As soon as closed loop occurs, the dwell goes to 2.9. However, the 02 sensor now reads less than 0.1 volts and the volts from the ecm is less than 0.1 volts. I can still get the dwell to rise up over 30 if I connect a 1.5v battery to the ecm side. Could something in the ecm be fried causing the new 02 sensor to go bad???? By the way, I plugged the air system in the exhaust and there was no change in dwell.

 

The ECM does not provide a voltage signal to the O2. The O2 provides a voltage signal to the ECM that is created as it heats up. The ECM ONLY responds to O2 voltage when it crosses (up or down in voltage) the rich/lean threshold. IIRC this is around 800 milivolts?

When you connect a 1.5 volt source to the O2 lead, the ECM sees the voltage cross the rich/lean threshold towards rich and responds by leaning the mixture (higher dwell=more time in the jets=less fuel). Because the ECM doesn't see the voltage cross the threshold back to rich it will peg the dwell full lean.

Don't over think this. The O2 doesn't tell the ECM how FAR it is out of adjustment, just when it crosses from rich to lean (and back). The ECM responds to the cross (rich/lean flag) by richening or leaning the mixture until it sees the flag again. Then it responds in the opposite direction. The ECM always hunts the proper settings, back and forth, from rich to lean. This is why you'll see the needle constantly wavering when it's operating correctly in feedback mode.

 

And don't connect a 1.5 volt source to the ECM lead for the O2. It's not designed for that voltage. I think Denn_Shah typed O2 when he meant 'TPS'.

In closed loop, once warm but without the O2 feedback, the system will operate on its 'last known good' data for dwell based on TPS and VAC sensors. You'll notice the dwell change as throttle and load change but you won't see the 'wavering' needle that indicates it's receiving feedback from the O2.

 

I only connected the 1.5v source to the ecm because there is a Pontiac shop manual posted on the "early third gen" web page that says it is OK for diagnosis. The main reason that I am confused is that I have another TA (1984) with the feedback carb and the dwell in closed loop varies about 30. So, when I see a constant 2.9, i figure something must be wrong. Now that the new o2 sensor reads less than 0.1 volts...is it now bad?? And what is causing the default to full rich?

 

Doesn't mean the O2 is bad just that it's either not getting hot enough or it's actually lean.

It's defaulting to full rich because the ECM is receiving a lean signal and the signal doesn't change (cross the lean/rich point) as the dwell drops. Keep in mind that the ECM is going to change dwell towards rich until it sees the voltage at the O2 change to rich. If this voltage doesn't cross back to rich the dwell will peg full rich and stay there... it's looking for the fence between rich and lean so it can jump back across. If the fence ain't there, it keeps going in the opposite direction.

This is why the carb needs to be adjusted so that the rich/lean flag point occurs near the middle of the scale (30 degrees or 50%). So it has the most room each side for adjustment.

 

Quick way to see if its just the carb running lean, put your hand over the air horn. It should lean it back out on the dwell.

 

In closed loop, when I put my hand over the air horn, the dwell does not change. The idle does not change unless I really choke off the engine. I will have to let it cool down to see in open loop.

 

It will only behave this way if it's in feedback mode and the carb adjustments are close enough for it to flag lean/rich. If it's as far out of whack as this one likely is, the ECM may still be stuck in non-feedback mode mode.

This is a good check to see that it's in closed loop though.

Use a rag to choke the airhorn. It can backfire while you do this.

 

Your hand wont do anyting for open loop.
So the new O2 sensor stays at .1 v?
Did you look at the tps and map..
Maybe clear the ecm memory and see what it does.

 

i did mean the computer side of the O2 sensor harness.
with the O2 sensor unplugged, key on engine off there should be about 0.450 volts on the wire.
the 0.450 volts is the bias voltage. if the bias voltage is too high (above about 0.550) or too low (below about 0.380), the ECM won't react properly to changes in the O2 sensor voltage.

when i test the computers' reaction to changes in O2 voltage, i put a jumper wire into the computer side O2 connector and hold the other end of the jumper wire with 1 hand and move my other hand between battery positive and negative.
if the system is reacting properly to O2 sensor input, you can vary the dwell from rich to lean by keeping your hand on the appropriate post longer.

with everything hooked up and with the system in closed loop, richening the mixture should cause a change in O2 voltage which should change the dwell.
propane, spray carb cleaner, or closing the choke should force it the run richer.

some kind of scan tool would be very helpful for what your doing.
with a scanner, you can see what all the sensors are reading along with changes in dwell. if you have a laptop, you can make either buy or make an ALDL cable and download the software to have a decent scan tool.
you can get the old Snap-On MT2500 pretty cheap on E-Bay now.
some for ~$100.00. if you go with one from E-Bay, make sure you buy from someone with a lot of great feedback and preferably local to you.

 

You have your loop's backwards. Open is a set map, looking at your normal sensors(tps/map). Closed loop is when its in feed back with the O2.
Once warmed up, it should be in closed loop. Just over part throttle it goes back into open loop, since these cars have a narrow band O2..

 

First thanks for all of the advice / suggestions. I want to make sure everyone has the proper info:

Open loop (cold engine start) - Dwell around 30 as high as 33. Engine seems to run smooth.

Closed loop occurs when temp is about 180 / 190 deg F. While watching the dwell meter, it tumbles right to 2.9 / 3.0. Runs very smooth. I blip the throttle and the dwell rises the first few times and then subsequent blips result in a steady 2.9.

Shut the car off for a few minutes. Restart and the dwell is again 30 ish until the temp rises and then the dwell drops to 2.9.

I disconnect the O2 sensor and apply a 1.5 VDC to the ecm wire and ground (per the Pontiac service manual). Dwell climbs to over 30. Disconnect and the dwell goes right back to 2.9. Placing my hand over the primaries does not change the dwell or RPM for that matter.

I have a 1984 TA same motor / set up and it does what it is supposed to. I do not believe I have a leak as no change in engine speed when partially choking the engine or pulling a vacuum line off. Carb and sensors check out. I just replaced the o2 again today to ensure that is not the issue. I have not measured its voltage for fear of ruining it. Temp sensor is new and checks out. If I put a high ohm resistor across the temp sensor it goes back into open loop and dwell rises. ???????????

Only code is 44 sometimes.

 

Fixed it, it was late in the afternoon, thanks.

 

It's functioning exactly how it's supposed to.

There are three (3) operating modes for the system: warm-up, open loop and closed loop. Your system is not going completely into closed loop.

When the CTS reaches set point, the ECM begins relying on the TPS and VAC sensors for input on varying dwell. The O2 is not yet providing feedback though and it is using the 'last known good' data stored (the ECM re-writes the blocks constantly while in closed loop based on O2 feedback). In this mode the dwell will change as you rev it but you won't see the needle waver as it adjusts.

As soon as your ECM sees data from the O2 it begins trying to compensate for the initial lean or rich flag it sees. In your case it sees a lean flag and it starts decreasing dwell to richen the mixture. Well it keeps decreasing the dwell but it never sees the rich flag telling it to go the other way. So it pegs out.

Bear in mind that this initial lean flag doesn't necessarily mean that the mixture is initially lean (although it is likely). The O2 sensor is not a very sophisticated device and is only reliable near the 'flag' voltage of 800-900mv.

I'm not sure I can explain it any better.