Bad hesitation and stall. HELP!!
07-17-2015, 02:53 PM
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Bad hesitation and stall. HELP!!
Hello fellow f150forum members. My dad has a 92' F-150 with a 351 5.8L.
The engine will do one of two things:
1) Not start at all
2) Run anywhere between 5-30 seconds normally then have severe hesitation for a few seconds before stalling.
Fuel system is at 35 PSI (spec is 30-40PSI KOER), flowing approximately 5oz. in 15 seconds. Most likely not fuel system related or bad gas as switching tanks makes no difference. The other tank was filled up at a different station.
Ignition coil is throwing a purple/blue spark and has very good fire.
No codes present.
Anyone have an idea what is going on?
New symptom...
Once engine dies, the coil continues to fire. Is this normal?
The TPS was replaced with motorcraft and adjusted to .9V CT and 4.5V WOT. Cleaned EEC connector at bulkhead.
Here is a video of it running then stalling.
The engine will do one of two things:
1) Not start at all
2) Run anywhere between 5-30 seconds normally then have severe hesitation for a few seconds before stalling.
Fuel system is at 35 PSI (spec is 30-40PSI KOER), flowing approximately 5oz. in 15 seconds. Most likely not fuel system related or bad gas as switching tanks makes no difference. The other tank was filled up at a different station.
Ignition coil is throwing a purple/blue spark and has very good fire.
No codes present.
Anyone have an idea what is going on?
New symptom...
Once engine dies, the coil continues to fire. Is this normal?
The TPS was replaced with motorcraft and adjusted to .9V CT and 4.5V WOT. Cleaned EEC connector at bulkhead.
Here is a video of it running then stalling.
07-17-2015, 03:31 PM
#2
Hello fellow f150forum members. My dad has a 92' F-150 with a 351 5.8L. The engine will do one of two things: 1) Not start at all 2) Run anywhere between 5-30 seconds normally then have severe hesitation for a few seconds before stalling. Fuel system is at 35 PSI (spec is 30-40PSI KOER), flowing approximately 5oz. in 15 seconds. Most likely not fuel system related or bad gas as switching tanks makes no difference. The other tank was filled up at a different station. Ignition coil is throwing a purple/blue spark and has very good fire. No codes present. Anyone have an idea what is going on? New symptom... Once engine dies, the coil continues to fire. Is this normal? The TPS was replaced with motorcraft and adjusted to .9V CT and 4.5V WOT. Cleaned EEC connector at bulkhead. Here is a video of it running then stalling. Video Link: https://www.youtube.com/watch?v=rn8LDNSHNng
Your computer that controls the electronic fuel injection might be going out if not already . When it was running did it use a lot of gas going short distances???
If it did, thats your problem . The computer was importing two much gas into the cylinders at once causing it to burn off before it gets to the engines combustion chamber .
07-17-2015, 05:03 PM
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Problem solved
I swapped out the computer with a friends truck and it stalled as well. Looks like its a bad PCM. Going to see if I can find one locally. Thank you for all the help!
07-17-2015, 10:35 PM
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Problem solved
These were my symptoms. Ignition coil fired and the IAC actuated even after engine was shut off!
Found a new EEC/PCM/ECM at a salvage yard off of a 92' F-150 that looked to be in good shape. The problem is solved.
Reason why the computer failed is simply this. The gasket in front of the computer was in poor shape and the case was rusty allowing moisture inside. Make sure your gasket is in good shape, this is critical because the PCM is not a sealed unit! After further investigation, all the electrolytic capacitors two 47uF and one 10uF have corroded into dust just about. Also worth noting, the electrolyte had leaked out of the capacitors and when this occurs, the PCB is eaten away by the acid it contains. I've attempted replacing them by wearing away the factory applied rubber coating off the solder side of PCB with a plastic spudger, not to cause more damage, but the pads where the capacitors go were too far gone, even after bridging a trace with a capacitor lead.
I'm surprised it ran as long as it did in that condition!
Found a new EEC/PCM/ECM at a salvage yard off of a 92' F-150 that looked to be in good shape. The problem is solved.
Reason why the computer failed is simply this. The gasket in front of the computer was in poor shape and the case was rusty allowing moisture inside. Make sure your gasket is in good shape, this is critical because the PCM is not a sealed unit! After further investigation, all the electrolytic capacitors two 47uF and one 10uF have corroded into dust just about. Also worth noting, the electrolyte had leaked out of the capacitors and when this occurs, the PCB is eaten away by the acid it contains. I've attempted replacing them by wearing away the factory applied rubber coating off the solder side of PCB with a plastic spudger, not to cause more damage, but the pads where the capacitors go were too far gone, even after bridging a trace with a capacitor lead.
I'm surprised it ran as long as it did in that condition!