Recurring misfire with code P1131

1999 FORD CROWN VICTORIA
270,000 MILES • 4.6L • V8 • 2WD • AUTOMATIC
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TFABE
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Had cylinder misfire when purchased car. Replaced spark plugs and coils, ran great for couple days,started running rough.trouble code said misfire #4 and 5.cleaned plugs,ran good for couple days then rough again trouble code said misfire #3 and 4, clean plugs and MAF. Ran good couple days, then rough again. Trouble code said misfire #4 and 5, cleaned, re-gapped plugs, reset PCM.ran good for about 4 days now rough. Trouble code now says misfire #1 and 3, also new trouble code P1131. What do I check or repair/replace next?
May 16, 2021 at 9:02 AM
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ASEMASTER6371
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Good afternoon,

I would check the compression to be sure it is not an internal engine issue.

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

I would also check the fuel pressure to be sure there is good pressure. Low fuel pressure will cause this issue.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Roy
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May 16, 2021 at 12:44 PM
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HARRY P
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Also if you bought aftermarket coils, they could be the issue. You might try sticking a few of the old ones back in if you still have them. In particular cylinders 1, 3, 4, and 5.
May 16, 2021 at 6:54 PM
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