Engine misfires only slightly?

1995 FORD F-250
72,000 MILES • 7.5L • V8 • 4WD • MANUAL
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WJBARNICKOL
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95 ford 460 engine has injector fire pulse of 5us but with a 0.2 us flicker. engine misfires only slightly. Does not change with RPM. drivability is very good. wont quite pass smog of less than 1 percent CO have replaced plugs, wires, ICM, coil. have tested fuel pressure, MAP, EGR idle air control. TPS,
Apr 18, 2026 at 4:56 PM
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STRAILER
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So there are a few things that can cause this issue.

1. Leaking or dirty injectors
2. Fuel pressure regulator
3. Engine coolant temperature sensor
4. O2 sensor lazy or biased rich
5. Exhaust leak ahead of O2
6. Compression issue on one cylinder
7. Base engine timing / distributor issue

Here is a guide to help fix the problem

https://www.2carpros.com/articles/why-an-automotive-engine-will-run-rich

Have you run the codes? This guide will show you how

https://www.2carpros.com/articles/ford-lincoln-mercury-obd1-1995-and-earlier-diagnostic-trouble-code-definition-and-retrieval

Also, please go over this video to help check the compression. If we have a problem here nothing above will fix it.

https://www.youtube.com/watch?v=KOxIm1F8AW0

Please go over these guides and get back to us.
Apr 19, 2026 at 8:48 AM
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WJBARNICKOL
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I get decent looking fire pluses from coil when cranking it into a spark plug,( no engine firing). When running the fire pulses are wildly erratic, vary by 10 to 1 voltage. And they are the same on all plugs.
Apr 22, 2026 at 7:48 PM
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STRAILER
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Did you run the codes to see if any are stored? Also I would check for vacuum leaks and I would replace the MAP sensor. What are the compression readings? Here is a video to help with the vacuum leak test.

https://www.youtube.com/watch?v=LRKWV4Are5c

Please go over this guide and get back to us.



Apr 23, 2026 at 7:49 AM