1987 454 TBI stalls at idle after a short time

[beady]

Well. So far i've been wondering why the speedometer is inop and I keep wondering about the exhaust manifolds you referenced more than once.
I also wondered if the rear air works and what color the truck is.

Cuz see there's no pix.
It's hard to tell what's goin on...buncha wondering!

This has been my favorite song before;

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Back to the manifolds though.
Maybe i'm wrong? but in some vehicles I know i've seen a fairly considerable ground strap attached to a manifold bolt through an "o ring". Yes.
AND THEN I questioned how the starter wires got hacked. Transmission RnR

OR

Has the motor been out too? The underhood presents very well but i'm not convinced. More information and some Dying Fetus IS necessary!
Tearing through the Womb - like your BigBlock!

Remember about the other ground strap that connects through the bellhousing?
AND what does the oil change sticker say FFS? F v ck Around and Fix It (FAFI) with some 10-30 and a Wix! wouldnt be the first time

How am I supposed to fix it when I don't even know what color it is?
MIKE

Th400 was rebuilt just before I bought it, so trans was definitely out. Don’t think engine was, but don’t know.

Rear AC doesn’t work (yet). I replaced the compressor, condenser, evaporator, dryer. I pulled and flushed rear evaporator and flushed all lines and hoses. I haven’t vacuumed everything and put r134 yet as I’ve been working on getting it running 100% now.

My plan was to replace most of the engine stuff I have already anyway, as it is supposed to be our backup horse trailer setup and I wanted to reset everything so it was reliable when we are hours from home.

Mike

 

[Rusty Nail]

Omg it's pretty!

You and Bill are gonna get it fixed - I was only helpin!
Yay! Go Team Swuarr Pody!


If the trans has been out I think chasing down the ground that is between the bell housing and the block is prolly a good idea. Wtf anyways??
You were talkin about fixing the starter wires. What else was over there that coulda got damaged also cuz why speedometer no work then?

Can we fix that too?

Trans rebuild
Speedometer
Starter wires
Rear Air
Ground at trans? Does that even exist? It's all in my imagination again Mike?

Lots of damage through that way. Wonder what they ran over or if they lost a u joint/driveshaft/somethin

Feel like i'm missing something but im madf sleepy. Good luck!

 

[Sgt Gus]

Th400 was rebuilt just before I bought it, so trans was definitely out. Don’t think engine was, but don’t know.

Rear AC doesn’t work (yet). I replaced the compressor, condenser, evaporator, dryer. I pulled and flushed rear evaporator and flushed all lines and hoses. I haven’t vacuumed everything and put r134 yet as I’ve been working on getting it running 100% now.

My plan was to replace most of the engine stuff I have already anyway, as it is supposed to be our backup horse trailer setup and I wanted to reset everything so it was reliable when we are hours from home.

Mike

Sweet burb. Horse trailering is one big reason my daughter wanted her 87 pickup.

 

[beady]

Been off on a dozen other things, and bought a 2005 LLY Duramax 3500 with blown head gasket, but back on trying to figure out what’s up with the Suburban.

Here are the cold engine, key on, engine off readings. I had a battery charger on the truck.

Resistance btwn D7 o2 sensor pin at ecu (unplugged) and o2 connector is 8-10 ohms. That’s through an aligator lead and a jumper cable to my meter, so is really a little lower probably.

I’m starting to wonder if it’s not the ECU/tune issue. The ECU is a reman, but I can’t read what was on the sticker. I looked up AZFT and it looks to be for 454/TH400 (correct for this truck). Which chip gets replaced if you get an aftermarket chip?

I’m considering just buying another stock AZFT chip to try. But that won’t tell me if the ECU itself is the problem.

Thoughts?

Thanks

 

[Bill USN-1]

about gave up on you.
Yes, AZFT is 454
You pinout shows that the O2 and the CTS readings are wrong.
But the log you sent shows a correct temp on it.
So you may have unplugged it.

I recommend checking/repairing the O2 wire from sensor to ECM or just run a new one and splice in on both ends.

If temp sensor is bad or disconnected, resistance will be high and the system will think it's -40* all the time.
Your logs showed ~190*
I doubt the ECM or chip is bad but...you could always send it to me and I can run it in one of mine.

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[beady]

about gave up on you.
Yes, AZFT is 454
You pinout shows that the O2 and the CTS readings are wrong.
But the log you sent shows a correct temp on it.
So you may have unplugged it.

I recommend checking/repairing the O2 wire from sensor to ECM or just run a new one and splice in on both ends.

If temp sensor is bad or disconnected, resistance will be high and the system will think it's -40* all the time.
Your logs showed ~190*
I doubt the ECM or chip is bad but...you could always send it to me and I can run it in one of mine.

You must be registered for see images attach

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Bill,

Temp sensor wasn’t unplugged or disturbed, don’t know what to say about that. On winALDL the temp matches reality, i.e., if it’s in the 60’s out and truck is cold it reads 60’s, then it climbs up to 190 ish or whatever as truck warms up. So it seems to behave normally?

So it seems the ECM uses the o2 reading to adjust the INT, which causes the BLM to adjust? So I started looking at the O2 more closely. With the sensor heated powered and the engine running, I backpinned the signal wire at the O2 sensor plug. The readings sits consistently high, just over 1 volt (wasn’t fully warmed up yet). I used to min/max function on the meter to be sure it just wasn’t fluctuating faster than I could see, but it was not. Video linked here:

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Next, I took a brand new single wire O2 sensor and bench tested it with a torch to make sure the way I was going to test the 3-wire would work. You can see the 1-wire produces a moving voltage as I heat/remove torch. Video:

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Next, I removed the heated 3-wire sensor from the truck and bench tested it in the same way, and it seems to react normally. Video:

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Then I put the 3-wire sensor back in the truck and backpinned the O2 sensor pin at the ECM. It read about the same reading. Then, after idling for a long time, it seemed to enter closed loop and the readings bounced from .1-.2 to .8-.9. Took the truck for a drive, but it doesn’t seem to ever enter closed loop. Video:

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So I get home and let it idle. And lo and behold it enters closed loop again for a few seconds. But that was it. It wouldn’t go back into closed loop again;

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Now, here’s maybe where you can tell me what’s going on. These are readings with the heated, 3-wire sensor (basically brand new, I tested it with torch in previous video), heater is ENERGIZED for these readings. Readings are taken by backpinnig the ECM O2 pin at the ECM connector. You can see in the video below that the voltage at the ECM pin has basically zero correlation with what winALDL is reporting what the ECM “thinks” the O2 readings are. What’s going on here?

https://youtu.be/OOb4IVnVoPY?si=wG75qmxMyzcc4qAH

I feel like this has to be the crux of whatever my issue is.

Thanks

Mike

 

[gmbellew]

how does the reading at the O2 sensor, if you backprobe it, compare to winALDL? wondering if you are probing the wrong pin?

some 454, I think, were set up to idle in open loop. that wouldn't explain why it wouldn't hit closed loop when off idle, especially if winALDL is showing the O2 voltage varying and the CTS is close to temp.

I dont remember if your truck is stock. but O2 being constantly above 0.9v while driving down the road is odd. is it really running that rich.

this is from the 91 drivability manual...

Run Mode The Run mode has two conditions called "Open Loop” and "Closed Loop.” Open Loop When the engine is first started, and it is above 400 rpm, the system goes into "Open Loop” operation. In "Open Loop,” the ECM/PCM ignores the signal from the O2 sensor, and calculates the air/fuel ratio based on inputs from the coolant temperature and MAP sensors. The system stays in "Open Loop” until the following conditions are met: 1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature.) 2. The Coolant Temperature Sensor (CTS) is above a specified temperature. 3. A specific amount of time has elapsed after starting the engine. The 7.4L engine is designed to operate "Open Loop” at idle. The system will go to "Closed Loop” when the rpm is increased and all conditions above are met. A normal functioning system may go into "Open Loop” at idle if O2 sensor temperature drops below the minimum requirement to produce voltage fluxuation. Closed Loop The specific values for the above conditions vary with different engines, and are stored in the Programmable Read Only Memory (PROM). When these conditions are met, the systems goes into "Closed Loop” operation. In "Closed Loop,” the ECM/PCM calculates the air/fuel ratio (injector on-time) based on the signal from the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.

 

[Bill USN-1]

You didn't show the connections on the 3 wire during testing but, the 2 wires that are the same color are the heater.
Makes no difference to + and-.
Most are blk.
The other wire is the sensor which is normally wht.

You should not need the torch to change voltage on a heated O2.
The heater will make it too hot to hold with power applied.
That's the only purpose of the heater.
When I bench test my systems I can go into closed loop on the bench.

I only use them when running long tube headers when the sensor is more than 18" from the engine and the sensor gets mounted in the collector.
A 1 wire would still work but it will drop into open loop in rain and winter conditions.
Not an issue if your base tune is correct.

 

[beady]

You didn't show the connections on the 3 wire during testing but, the 2 wires that are the same color are the heater.
Makes no difference to + and-.
Most are blk.
The other wire is the sensor which is normally wht.

You should not need the torch to change voltage on a heated O2.
The heater will make it too hot to hold with power applied.
That's the only purpose of the heater.
When I bench test my systems I can go into closed loop on the bench.

I only use them when running long tube headers when the sensor is more than 18" from the engine and the sensor gets mounted in the collector.
A 1 wire would still work but it will drop into open loop in rain and winter conditions.
Not an issue if your base tune is correct.

3-wire O2 was unpowered, unheated while I was bench testing it. I was only measuring the element response. One probe to sensor pin/wire, the other to O2 case/ground.

The 3-wire sensor WAS heated when installed in the truck and showing readings at the ECM pin.

Is there any reason that winALDL would return values that don’t correspond to what the voltage is on the O2 sensor pin at the ECM connector reads? Because that is what I’m seeing.

how does the reading at the O2 sensor, if you backprobe it, compare to winALDL? wondering if you are probing the wrong pin?

some 454, I think, were set up to idle in open loop. that wouldn't explain why it wouldn't hit closed loop when off idle, especially if winALDL is showing the O2 voltage varying and the CTS is close to temp.

I dont remember if your truck is stock. but O2 being constantly above 0.9v while driving down the road is odd. is it really running that rich.

this is from the 91 drivability manual...

Run Mode The Run mode has two conditions called "Open Loop” and "Closed Loop.” Open Loop When the engine is first started, and it is above 400 rpm, the system goes into "Open Loop” operation. In "Open Loop,” the ECM/PCM ignores the signal from the O2 sensor, and calculates the air/fuel ratio based on inputs from the coolant temperature and MAP sensors. The system stays in "Open Loop” until the following conditions are met: 1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature.) 2. The Coolant Temperature Sensor (CTS) is above a specified temperature. 3. A specific amount of time has elapsed after starting the engine. The 7.4L engine is designed to operate "Open Loop” at idle. The system will go to "Closed Loop” when the rpm is increased and all conditions above are met. A normal functioning system may go into "Open Loop” at idle if O2 sensor temperature drops below the minimum requirement to produce voltage fluxuation. Closed Loop The specific values for the above conditions vary with different engines, and are stored in the Programmable Read Only Memory (PROM). When these conditions are met, the systems goes into "Closed Loop” operation. In "Closed Loop,” the ECM/PCM calculates the air/fuel ratio (injector on-time) based on the signal from the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.

It does smell rich when driving.

I was reading voltage at the O2 pin at the ECM and the readings are far different than winALDL reports (see last video in my previous post). I checked continuity of the wire from ECM pin to o2 connector pin, and the voltage readings at the ECM pin fluctuate in the range an o2 sensor would, so confident the pin I’m metering is correct.

Thanks

 

[Sgt Gus]

Great read to learn from.
I was thinking of getting a backup ecm, and chip burn gear so I can work with a programmer/tuner.

 

[Bill USN-1]

If you feel the sensor is good but the ECM is not reading it correctly, then it's possible the input circuit of the ECM was damaged.
The logs you did shows the O2 at .451-.455 which is normal cold engine reading but, as we discussed early on, it is also what the ECM will display if you unplug the O2 sensor.
The ECM does not go into closed loop until the O2 gets to .600mv.

The O2 uses a signal and a gnd provided by the ECM.
Did you verify the sensor gnd to the engine from D6?
Your voltage checks did not list any of the ground readings for the system or the sensor grounds.

There's normally a protection circuit on the input to the ECM.
If, voltage was connected to D6 or D7 during the wiring change to a heated O2, it could have damaged the input circuit.

You must be registered for see images attach

 

[Bill USN-1]

Great read to learn from.
I was thinking of getting a backup ecm, and chip burn gear so I can work with a programmer/tuner.

All you need is the aldlcable to log a good data drive and someone to adjust the tune and burn it to a new chip.
If someone is going to just send you a tune, they are not the right person to use.
I've been helping DIY guys for over 20yrs.
Everything is documented in the injection forum at www.binderplanet.com
I'm Bill Hamilton of HamiltonFuelInjection.com
28yrs retired Navy.

 

[beady]

If you feel the sensor is good but the ECM is not reading it correctly, then it's possible the input circuit of the ECM was damaged.
The logs you did shows the O2 at .451-.455 which is normal cold engine reading but, as we discussed early on, it is also what the ECM will display if you unplug the O2 sensor.
The ECM does not go into closed loop until the O2 gets to .600mv.
The O2 uses a signal and a gnd provided by the ECM.
Did you verify the sensor gnd to the engine from D6?
There's normally a protection circuit on the input to the ECM.
If, voltage was connected to D6 or D7 during the wiring change to a heated O2, it could have damaged the input circuit.

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Bill, I have not checked d6 to ground, will today after work.

I used a 3-wire to 1-wire adapter harness. It just has flying leads for +12 and ground and a mating cylindrical connector for the existing 1-wire connector on the factory body loom. So I didn’t do anything to have put power on d6 or d7.

Also, the truck behaved this way the 1-wire o2 that was on it when I bought it, and with the name brand replacement 1-wire o2 sensor I tried after that, and before trying the heated 3-wire to see if it would help.

Thanks,

Mike

 

[beady]

If you feel the sensor is good but the ECM is not reading it correctly, then it's possible the input circuit of the ECM was damaged.
The logs you did shows the O2 at .451-.455 which is normal cold engine reading but, as we discussed early on, it is also what the ECM will display if you unplug the O2 sensor.
The ECM does not go into closed loop until the O2 gets to .600mv.

The O2 uses a signal and a gnd provided by the ECM.
Did you verify the sensor gnd to the engine from D6?
Your voltage checks did not list any of the ground readings for the system or the sensor grounds.

There's normally a protection circuit on the input to the ECM.
If, voltage was connected to D6 or D7 during the wiring change to a heated O2, it could have damaged the input circuit.

You must be registered for see images attach

Bill, just found this thread where the OP sounds like he has the same issue I do (no O2, int, blm cells populate). His issue was a chip burned to ignore the o2. I did get the o2 cells to populate a couple cells one time on one of the earlier data logs I posted, so I’m not sure it’s apples to apples, but figure I’d throw it out there.

https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050119-2-054370.html

 

[Bill USN-1]

Bill, just found this thread where the OP sounds like he has the same issue I do (no O2, int, blm cells populate). His issue was a chip burned to ignore the o2. I did get the o2 cells to populate a couple cells one time on one of the earlier data logs I posted, so I’m not sure it’s apples to apples, but figure I’d throw it out there.

https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050119-2-054370.html

I would recommend going back to the voltage/ground check sheet and testing all the grounds.
Here's the checklist in an Excel sheet