1987 454 TBI stalls at idle after a short time

[gmbellew]

^Both yalls problem could be a random short somewhere? IMO if a condition is random it’s less likely to be a bad component. Maybe talkin out my …. But my 2c anyway

I've had intermittent short to ground issues on ECMB and ECMI circuits kill the engine. usually it blows a fuse. but sometimes I think it might interfere just enough to kill the engine, but not blow the fuse until it really shorts.

I've also had a cracked distributor cap cause similar intermittent issues bc it sends stray currents on the ICM wiring.

 

[beady]

This is so similar to my intermittant problem where the truck just shuts off randomly - it hadn't happend for a few months and then just Tuesday I was riding along and had total power loss (but ignition was still on/live because all gauges were still responding, alternator was still outputting 13+ volts, radio still on, etc). I was going fast enough that the tranmission stayed engaged - which still weirds me out because I didn't think automatics could do that - so I rolled the key back to "OFF" and back to "ON". Engine immediately refired and ran fine. When it happens at idle I can confirm there is no spark/injector pulse until key is switched off, and then works properly immediately when turned back on.

I have been trying for almost a year now to hunt down anything that can provide live ALDL data - I hear rumors of such devices existing but have yet to meet a single person who has ever actually seen/used one. I figure its either an internet rumor or for some reason they have all been pulled from circulation. Maybe they no longer exist because of legal/intellectual property complications (since it is a GM propriatary system)?

I had an OTC scanner that would show you data. But not graphically, and it got stolen. I ordered an ALDL usb cable yesterday, hopefully I can get it to work. It seems very difficult to find any of the scanners that read ALDL data currently for some reason

Previously, I did have a problem with some of the small positive wires down by the starter. One was crushed btwn the sheet metal heat shield and block and had been worn through but for a single strand. If that strand grounded it would kill power to half the ecu, intermittently, and without blowing a fuse. It would stop the fuel pump circuit part of the ecu, but it would still crank and run on ether. Took a lot of schematic tracing and meter checking wires to find that one. That’s not what it’s doing currently though.

Timing is on point, with and without esc wire connected, rechecked fuel pressure and is solid 12 psig, even when it stalls out.

Going to try adjusting and resetting tps next, while waiting for ALDL cable.

Mike

 

[beady]

I bought the allocable.com usb cable. I could not get it to work. When my truck comes back from the rest shop I need to use it.

It is a Windows issue and I have not been able to get the software to see it even though windows sees it.

I ordered a cable. That’s my concern too, that it’s going to be a pita to get working without downloading a bunch of different softwares. I just want the easy button approach. Nothing fancy, no timing, etc., for now, just be able to see live data.

 

[Bill USN-1]

I ordered a cable. That’s my concern too, that it’s going to be a pita to get working without downloading a bunch of different software. I just want the easy button approach. Nothing fancy, no timing, etc., for now, just be able to see live data.

The cable comes with a CD or optional thumb drive full of free software.
For the C3 ECM like your 1227747, I prefer to use winaldl. Much easier than tunerpro for beginners.
Following directions is key.
Everyone want to just grab the cable and plug it in and then complain when it doesn't work.
NO, it's not an OBDII reader.
Live data is very limited.
The cable/laptop allows it to provide live data and more important, historical data logs so an entire log can be recorded and viewed from key on to key off.
I do not believe in part swappers.
I trouble shoot with data.

Interesting that you mentioned a previous problem that was shorting the system.
That could be the source of your problem.
These are computers.
If you short the voltage or connect a battery backwards or leave a ground disconnected/broken after doing poor maintenance, it will damage the electronics.
Just as someone just mentioned, a bad distr cap/plug/wire will cause the spark to jump to the closest ground it can find.
If you can clip a timing light on the plug wire and read timing, that same pulse will be sensed by the ECM.
RPM will falsely spike and the ECM will try to adjust timing and fuel to the false RPM.
A half second later it tries to go back to normal.
Never allow plug/coil wires to lay on the engine or wiring.

I have been building custom systems for over 20yrs using the GM TBI/MPFI system.
I have them on everything from amphicars to flatheads to updraft industrial cranes.
The system works.
It's people that mess it up.

 

[Bill USN-1]

For all of you, here's a couple basics.
The ECM connectors can built up light corrosion and cause intermittent issues.
Unplug the ECM and use some electrical cleaner or WD to clean both sides then blow out any residue.
Open the little 2 screw cover and rock the large chip slightly so it will clean contacts then push straight down to make sure it's seated.
I don't recommend removing the chip carrier if you're not familiar, you can damage one of the legs on the chip.

GM TBI basics.
There's only 3 parts to make spark and the ECM has nothing to do with it.
1. Distr pickup creates a small sine wave that is sent to the ignition module.
2. The module has 2 functions.
Amplify and convert the signal to fire the coil and also send the tach/DRP-distr ref pulse to the ECM.
3. coil

Fuel
For safety, there is no fuel if there's no spark.
on key-on, the ECM will prime the system by running the pump for 2sec. Some HD 7.4 included a fuel pump module that operated the pump for up to 30sec to help clear heat/vapor from the lines.
Pump will not turn back on until the ECM receives the DRP from the ign module.
You must have the key off for 7sec before you can prime the pump again due to the shut down cycle of the ECM.

Once the engine gets above 400rpm, the ecm will apply the modified timing signal to the ign module for timing control.
This allows an easy cranking with just the base timing, normally 0*.

WINALDL
DO NOT LET IT INSTALL TO THE DEFAULT DIRECTORY.

You must be registered for see images attach

CHANGE TO THIS.

You must be registered for see images attach

IT SHOULD NOW BE IN IT'S OWN FOLDER ON THE C: DRIVE.

You must be registered for see images attach

SETUP DATALOGGER LIKE THIS.

You must be registered for see images attach

INSTALL CABLE DRIVER INCLUDED ON CD
CONNECT CABLE
TOGGLE COM PORT IN CONFIGURATION UNTIL YOU GET AN "OK"

You must be registered for see images attach

GO KOEO
YOU SHOULD GET A BLINKING GREEN 20 IN THAT LITTLE BOX IN THE MIDDLE OF THE TOOL BAR.

 

[beady]

The cable comes with a CD or optional thumb drive full of free software.
For the C3 ECM like your 1227747, I prefer to use winaldl. Much easier than tunerpro for beginners.
Following directions is key.
Everyone want to just grab the cable and plug it in and then complain when it doesn't work.
NO, it's not an OBDII reader.
Live data is very limited.
The cable/laptop allows it to provide live data and more important, historical data logs so an entire log can be recorded and viewed from key on to key off.
I do not believe in part swappers.
I trouble shoot with data.

Interesting that you mentioned a previous problem that was shorting the system.
That could be the source of your problem.
These are computers.
If you short the voltage or connect a battery backwards or leave a ground disconnected/broken after doing poor maintenance, it will damage the electronics.
Just as someone just mentioned, a bad distr cap/plug/wire will cause the spark to jump to the closest ground it can find.
If you can clip a timing light on the plug wire and read timing, that same pulse will be sensed by the ECM.
RPM will falsely spike and the ECM will try to adjust timing and fuel to the false RPM.
A half second later it tries to go back to normal.
Never allow plug/coil wires to lay on the engine or wiring.

I have been building custom systems for over 20yrs using the GM TBI/MPFI system.
I have them on everything from amphicars to flatheads to updraft industrial cranes.
The system works.
It's people that mess it up.

Thanks Bill,

Sorry, for the long post below:

When I said I don’t need “timing” in that post, I had typed “tuning” and it got autocorrected. For now I just want the easiest software install that isn’t going to give me fits about PC operating system not being the right version, etc. I can worry about the extra bells and whistles like being able to actually tune later.

That previous shorting issue, there were two wires off the starter solenoid (as I recall, it was many months ago). One had been worn through the insulation, and you could see it had been like that for a while. The other wire had actually been worn completely through, and that was my issue at that time. I drove the truck for an hour with zero issues, turned it off for 2 mins, and when I went to fire it up again, it would crank (turn over) fine, but no fuel from the injectors. The last strand of wire that had been hanging on must have failed during the drive/right when the engine was turned off. I had to have it towed home. It would run fine on staring fluid. All fuses were fine, and after tracing schematics and what parts of which circuits weren’t getting power, I traced the issue back to the failed wire off the starter solenoid. I cut back, soldered and heat shrinked them for a secure repair. The truck started immediately and ran the same as it had before that for a couple months. So I don’t think that had any lasting effects.

The truck has had several of the ground wires replaced. I bought the truck this summer, so I don’t know what all was done to it in its past.

I pulled the EGR and it looked clean and worked fine with vacuum. The diaphragm is not ruptured, and didn’t leak. I reinstalled the EGR.

I went to check the vacuum (it looked about 17-18” at idle) and found the vacuum line to the smog pump/solenoid was off. I plugged that line temporarily (to take a pump/solenoid leak out of the equation) and it didn’t make any difference. I disconnected the battery for 30 seconds to clear any codes, and still no difference.

The tank still read about 1/8 th tank, and I wasn’t 100% if the last few gallons of gas I had gotten might not have had some water in it, so I went and got a few gallons from a different station and put it in the truck. Started the truck from dead cold, it idled happily and I walked away. A few minutes later it just stopped. No surge or trying to catch itself.

I disconnected the ESC wire and started truck again. Idle wasn’t as smooth or as low, but it seemed mostly happy. I let it warm up idling with the ESC wire disconnected for 10-15 mins with zero issues. Turned off truck, and reconnected ESC wire and started truck. Idled great, and smoothly. Let it run maybe 10 mins like that, no issues.

Drove truck to gas station and put in 5 more gallons. Drove for 30-40 mins, zero issues. Added another 5 gallons (turning truck off each time), and drove another 30-40 mins with no issues at all.

So wondering if perhaps my first issue was the vacuum line had come loose, and perhaps some crappy fuel and/or it was at the point of running out of fuel? (Not sure I’d run the tank that low before, so don’t know how accurate the gauge is/isn’t).

I still want to get the ALDL cable working with a laptop so I can really see what’s going on with all the sensor readings, etc.

Thanks again for your help,

Mike

 

[beady]

For all of you, here's a couple basics.
The ECM connectors can built up light corrosion and cause intermittent issues.
Unplug the ECM and use some electrical cleaner or WD to clean both sides then blow out any residue.
Open the little 2 screw cover and rock the large chip slightly so it will clean contacts then push straight down to make sure it's seated.
I don't recommend removing the chip carrier if you're not familiar, you can damage one of the legs on the chip.

GM TBI basics.
There's only 3 parts to make spark and the ECM has nothing to do with it.
1. Distr pickup creates a small sine wave that is sent to the ignition module.
2. The module has 2 functions.
Amplify and convert the signal to fire the coil and also send the tach/DRP-distr ref pulse to the ECM.
3. coil

Fuel
For safety, there is no fuel if there's no spark.
on key-on, the ECM will prime the system by running the pump for 2sec. Some HD 7.4 included a fuel pump module that operated the pump for up to 30sec to help clear heat/vapor from the lines.
Pump will not turn back on until the ECM receives the DRP from the ign module.
You must have the key off for 7sec before you can prime the pump again due to the shut down cycle of the ECM.

Once the engine gets above 400rpm, the ecm will apply the modified timing signal to the ign module for timing control.
This allows an easy cranking with just the base timing, normally 0*.

WINALDL
DO NOT LET IT INSTALL TO THE DEFAULT DIRECTORY.

You must be registered for see images attach

CHANGE TO THIS.

You must be registered for see images attach

IT SHOULD NOW BE IN IT'S OWN FOLDER ON THE C: DRIVE.

You must be registered for see images attach

SETUP DATALOGGER LIKE THIS.

You must be registered for see images attach

INSTALL CABLE DRIVER INCLUDED ON CD
CONNECT CABLE
TOGGLE COM PORT IN CONFIGURATION UNTIL YOU GET AN "OK"

You must be registered for see images attach

GO KOEO
YOU SHOULD GET A BLINKING GREEN 20 IN THAT LITTLE BOX IN THE MIDDLE OF THE TOOL BAR.

That’s super helpful info on the WINALDL, thanks!

Cable should be here Thursday it says. It’s one of my son’s old laptops, I think he said windows 7? I need to boot it up and check.

Mike

 

[edgephoto]

My Laptop is running Windows 10 and keeps trying to get my to go to Win 11.

I am not saying the cable is no good. I only tried for a few minutes and when it didn't work I put it away. My truck was headed to the body shop that day and I just needed to check/set the TPS voltage. When it comes back from restoration I will mess with it some more.

I plugged in the cable like it said in the instructions but it never popped up asking for a driver. When I loaded WinALDL nothing would communicate and on closing the program it gave a warning about COM port 4. In Device manager under COM port it showed the cable as being connected. I tried updating the driver using the one on the USB drive and it would not load it, said it was the latest already installed.

Beyond that I have not tried to trouble shoot it. Maybe things are different for Win 10?

I diagnose before replacing parts. I am a Field Engineer for a major car manufacturer and I do this for my day job. Albeit with much more sophisticated equipment than we had available to us back in 1987. I have been in the auto service business since 1985. I just want to read the data the ECM is getting. I don't need to tune, I don't need to graph or any fancy features. Just the fault codes and the data stream.