Hi everyone,
I’m currently trying to diagnose an issue with my 1990 Mustang GT 5.0 HO with an A9L ECU, and I’m running out of ideas.
Recently I removed and reinstalled the intake manifold. The distributor was also removed during the work. I replaced the distributor O-ring and afterward reset the ignition timing to 10° BTDC with the SPOUT connector removed.
I also refilled and bled the cooling system and replaced the previously installed 180°F thermostat with the factory-spec 195°F thermostat.
After putting everything back together, the engine initially ran fine. During one extended idle session (burping cooling system) it ran for approximately 1.5 hours before it suddenly started shutting off. At first I suspected a heat-related issue, but now it can sometimes happen only a few minutes after a cold start.
Symptoms
The engine starts and initially runs normally. It responds normally to throttle.
Then, without warning, it shuts off instantly. There is no stumbling, sputtering, or gradual drop in RPM beforehand. It feels almost exactly like somebody turned the ignition key off.
It will then restart immediately.
I have also manually operated the throttle at the throttle body and held the engine above idle. It has still shut off suddenly while doing this, so I’m starting to think this is probably not simply an IAC/base-idle issue.
When the engine shuts off, the tachometer drops very quickly/instantly to zero. I can also sometimes hear several relays clicking immediately after the engine dies.
What I have checked/done so far
My current main suspect is the PIP sensor (Hall-effect sensor) inside the distributor, especially since this is still the original Ford distributor.
What makes me hesitant is that the problem appeared immediately after the intake/distributor work, so I’m also considering a damaged/loose distributor or TFI connector, wiring issue, EEC power relay, ignition coil, fuel pump relay, or another power-supply issue.
Has anyone experienced this exact behavior on a Foxbody?
In particular, can a failing PIP cause this exact pattern:
Runs normally → instantly shuts off like the key was turned off → immediately restarts
And is there a good way to monitor/test the PIP/TFI/EEC signals on an A9L car while the failure occurs, so I can confirm what signal is disappearing before replacing the distributor or PIP?
Thanks!
Florian from Germany
I’m currently trying to diagnose an issue with my 1990 Mustang GT 5.0 HO with an A9L ECU, and I’m running out of ideas.
Recently I removed and reinstalled the intake manifold. The distributor was also removed during the work. I replaced the distributor O-ring and afterward reset the ignition timing to 10° BTDC with the SPOUT connector removed.
I also refilled and bled the cooling system and replaced the previously installed 180°F thermostat with the factory-spec 195°F thermostat.
After putting everything back together, the engine initially ran fine. During one extended idle session (burping cooling system) it ran for approximately 1.5 hours before it suddenly started shutting off. At first I suspected a heat-related issue, but now it can sometimes happen only a few minutes after a cold start.
Symptoms
The engine starts and initially runs normally. It responds normally to throttle.
Then, without warning, it shuts off instantly. There is no stumbling, sputtering, or gradual drop in RPM beforehand. It feels almost exactly like somebody turned the ignition key off.
It will then restart immediately.
I have also manually operated the throttle at the throttle body and held the engine above idle. It has still shut off suddenly while doing this, so I’m starting to think this is probably not simply an IAC/base-idle issue.
When the engine shuts off, the tachometer drops very quickly/instantly to zero. I can also sometimes hear several relays clicking immediately after the engine dies.
What I have checked/done so far
- Replaced/swapped the TFI ignition module – no change
- Ignition timing set to 10° BTDC with SPOUT disconnected
- Distributor is still the original Ford distributor
- Distributor was removed during the intake manifold work
- Replaced distributor O-ring
- Engine responds normally to throttle
- Engine can still shut off with the throttle manually held open
- Disconnected the IAC while running as a test; engine would not continue idling without it
- Cooling system has been refilled and bled
- Checked spark plugs from cylinders 1, 4, 5 and 8 for signs of coolant entering the cylinders – nothing abnormal found
- No obvious evidence of coolant entering the combustion chambers
- Engine otherwise sounds mechanically normal
- It immediately restarts every time it shuts off
My current main suspect is the PIP sensor (Hall-effect sensor) inside the distributor, especially since this is still the original Ford distributor.
What makes me hesitant is that the problem appeared immediately after the intake/distributor work, so I’m also considering a damaged/loose distributor or TFI connector, wiring issue, EEC power relay, ignition coil, fuel pump relay, or another power-supply issue.
Has anyone experienced this exact behavior on a Foxbody?
In particular, can a failing PIP cause this exact pattern:
Runs normally → instantly shuts off like the key was turned off → immediately restarts
And is there a good way to monitor/test the PIP/TFI/EEC signals on an A9L car while the failure occurs, so I can confirm what signal is disappearing before replacing the distributor or PIP?
Thanks!
Florian from Germany
