3fe Increasing idle, dies when accelerating (1 Viewer)

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So... I've done everything I could find on the forums. I've adjusted the new tps I put in. Bought and replace IAC. Replaced fuel pump. Bought new intake boots. Bought new afm, new TB gasket, adjust and lubed the dashpot. Replaced efi relay etc... I still get the issue. I drove it for about a week after I replaced everything and it was fine until yesterday morning. Not sure what else to do short of replacing the entire harness. Any other suggestions?
 
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No sir, it will give me problems unless I shut the key off completely and wait 10-15 seconds minimum and even then struggles a bit. If I dont shut the key off at all it won't start at all
 
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Seems to run fine when I let the electronics reset with the positive battery cable disconnected. After driving and getting hot for a while it reverts back to this issue. If I dont let it stay warm for a while, <20 minutes, I don't have the issue. CEL comes on very briefly when the issue comes back but always goes away and is never persistent enough for me to read it.
The ECU will keep stored codes until a reset. You can read them even if the CEL is not illuminated.
 
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No sir, it will give me problems unless I shut the key off completely and wait 10-15 seconds minimum and even then struggles a bit. If I dont shut the key off at all it won't start at all
When the engine stalls and you leave the key in the ON/RUN position, is the CEL illuminated?
 
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So the CEL is on before the issue occurs. Once the idle increases the CEL shuts off and doesn't come back on until get it started again.

So short answer no.
 
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So the CEL is on before the issue occurs. Once the idle increases the CEL shuts off and doesn't come back on until get it started again.

So short answer no.
You misunderstand.
When the motor stalls out BEFORE YOU SHUT OFF THE IGNITION SWITCH, is the CEL illuminated.
I ask this specifically because WITHOUT THE MOTOR RUNNING with the ignition switch in the ON/RUN position, the CEL MUST BE ON FOR THE MOTOR TO RUN.
If the CEL is not on with the key in the ON position WITHOUT the motor running, it indicates the the ECU is not in a "ready" state.
 
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Got it thank you.

Yeah the CEL is off after motor dies, when key is left in the on/run position
OK. You need to verify that the ECU is still receiving power when it is in that state.
First check would be to verify that pin 8 (B+) of the diagnostic connector on the firewall is at +12. This verifies that the EFI relay has closed and is feeding +12 to the ECU and the rest of the sensors.
I would also replace the 3 fusible links off the positive battery terminal if that hasn't been done. They should be changed with every battery replacement as they are susceptible to vibration fatigue and can become intermittent.
 

tlc1995

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Maybe something with your battery itself or the wiring from it is loose or shorting something causing a Domino effect or it's Chyna Wu flu Covid 20. I pray it's not the latter.
 
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I had a high idle issue in my 92 that wasn’t quite like yours, but after all the FSM diagnostics, it turned out to be caused by clogged coolant lines in/out of the IAC. Wouldn’t hurt to make sure yours are clear.
Sorry for this but what is the IAC?
 
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So, I did a few more things that include changing the fusible link that looked like it was the original, new oem vacuum lines, reset timing and again adjusting the dashpot. Is definitely running better but the issue persisted enough for me to take it to a garage. Their first guess is the cold start injector sensor on the t-stat housing which snapped off when I changed out the old cracked housing. Saw a few threads that basically say it doesn't affect much if broken off except longer start times. Their second guess is the distributor. I can do both of those jobs myself so I picked up the truck and am hoping to hear your guys thoughts on those 2 possibilities.
 
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So, I did a few more things that include changing the fusible link that looked like it was the original, new oem vacuum lines, reset timing and again adjusting the dashpot. Is definitely running better but the issue persisted enough for me to take it to a garage. Their first guess is the cold start injector sensor on the t-stat housing which snapped off when I changed out the old cracked housing. Saw a few threads that basically say it doesn't affect much if broken off except longer start times. Their second guess is the distributor. I can do both of those jobs myself so I picked up the truck and am hoping to hear your guys thoughts on those 2 possibilities.
Once again...
If the CEL is NOT illuminated with the key in the ON/RUN position, the ECU is not in a "ready" state and this engine WILL NOT RUN.
The distributor will not effect the CEL.
The cold start injector will not effect the CEL.
The ignition coil will not effect the CEL.
The igniter will not effect the CEL.

I suspect you have an intermittent electrical connection. You are not popping fuses, so you don't have a short.

Have you downloaded the 3FE EFI troubleshooting document that I posted?
 
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Sorry Jon, forgot to add in my synopsis I did find an intermittent ground to the ecu. I fixed that and the cel is now on when the key is on pre-start up.

Bought new grounding cables from a fellow mudder.

Got the efi troubleshooting guide and I bought the FSM although that hasn't arrived yet
 
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Sorry Jon, forgot to add in my synopsis I did find an intermittent ground to the ecu. I fixed that and the cel is now on when the key is on pre-start up.

Bought new grounding cables from a fellow mudder.

Got the efi troubleshooting guide and I bought the FSM although that hasn't arrived yet
Please elaborate. Where was the intermittent ground to the ECU?
 

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