Runs rough and backfires

Hi and thanks for using 2CarPros.

The fuel pressure is right where it should be. Has this engine ever run correctly since it was installed? Have you checked for vacuum leaks? Have you checked to make sure the catalytic converters aren't plugged.

Take a look through these links and let me know if anything mirrors what you are experiencing and if it is helpful.

https://www.2carpros.com/articles/engine-backfires-while-running

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

The reason I asked if it ever ran properly is because the engine you got could have timing issues, burnt valves and the list goes on, However, most times, it is a vacuum leak causing what you described.

Let me know if this helps.

Joe

Welcome back:

Lets start at the beginning. I need you to check engine compression. Sometimes a "running" engine from a salvage yard is just that. Running, but no one indicates how it is running. At least if we have compression readings, we will know if there is a weak cylinder, timing is out, or if it is the engine itself rather than trying to find problems with other things on the vehicle that aren't bad. You know the car, but the engine is new.

Here is a link that shows how to check compression in general:

https://www.2carpros.com/articles/how-to-test-engine-compression

Here are the specific direction for testing compression on your vehicle:

AllData Editors Note - Ford does not provide a cranking pressure specification, only an acceptable range.

1. Make sure oil in crankcase is of the correct viscosity and at proper level and battery is properly charged. Operate vehicle until engine is at normal operating temperature. Turn ignition switch to the OFF position, then remove all spark plugs.
2. Install a compression gauge such as Rotunda Compression Tester 164-R0250 or equivalent in No.1 cylinder.
3. Install an auxiliary starter switch in starting circuit. With ignition switch in the OFF position, and using auxiliary starter switch, crank engine a minimum of five compression strokes and record highest reading. Note the approximate number of compression strokes required to obtain the highest reading.
4. Repeat test on each cylinder, cranking the engine approximately the same number of compression strokes.

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Compression Analysis, see two attached pics.

Ford does not provide a cranking pressure specification, only an acceptable range.

The indicated compression pressures are considered within specification if the lowest reading cylinder is within 75 percent of the highest reading. Refer to the Compression Pressure Limit Chart.

If one or more cylinders reads low, squirt approximately one tablespoon of clean engine oil meeting Ford specification WSS-M2C153-G on top of the pistons in the low-reading cylinders. Repeat the compression pressure check on these cylinders.

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We need to determine if the engine is the problem. This is what I feel needs done first.

Let me know the results or if you have other questions.

Joe