My stock 86 SVO 39000 miles. I have an erratic misfire under light accel below 3000 RPM that started a week ago. Before this it was purring. I cleaned the VAM and the ducting of oil. I ran codes and nothing showed up. Misfire was getting worse. I measured the resistance on the coil both primary and secondary. Secondary was 35k ohms. The coil was OEM and so i replaced it. Car is running better. Still misfires but not as severe. I bought a TFI and was going to test the old TFI. Upon removal of the old orig. TFI the contacts broke off, no test. This was an OEM motorcraft part. I installed the new TFI, set base timing at 10 deg. with computer out of loop, and checked 30deg with it in loop. Still missing but also a bit better. I started pulling the wires off the dist. with the motor running and cyl. 3 was dead. I got zapped so there is current. I pulled the plug checked gap and compression. There was over 120 psi on 3 cranks. Reinstalled the plug and wires. Inspected the harnesses, did a wiggle test no changes. Next day I suspected that maybe i have a bad injector in hole 3 (these were changed out a year ago with new from Advance auto). Started motor and guess what, misfire is gone engine is idling smooth. I listen to all the injectors with a long screwdriver and i can hear them all clicking with the same frequency. Car warms enough that the electric fan cycles. I go for a 15 minute ride. Car runs great on the way out. Then starts to hesitate under light accel, getting worse. I get back to the drivway and the motor is shaking and missing. I am stumped?
86 Svo Misfire
- Thread starter stockman1
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fess40
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fess40
Founding Member
Odd that it wouldn't throw a code at all running that rough. Did you change the PIP when you changed out the TFI. I haven't had to change either one before but I've heard they can effect things when the car warms up. It's been a few months, any changes?
65ShelbyClone
Founding Member
Did you only spin it over three times? Was the throttle wide open? Usually a compression test is done with the throttle open and the engine cranked until pressure stops rising.
I observed mid-140s with an SVO that had at least 180,000mi on it. The 214k mile 2.3T I'm wrenching on now registered more than 120psi on the lowest hole after it had been sitting for about seven years.
There is a special test mode available in many of Ford's EEC-IV systems called the Continuous Monitor Diagnostic Test Mode or "wiggle test." It is designed to trip a code whenever there is a fault detected, even if the fault wouldn't normally trip one. I'm just not sure if the 2.3T systems had it. Here is a good rundown of how to use it: http://www.ford-trucks.com/forums/1026682-special-test-mode-what-does-this-do.html
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