Cylinder 5 misfire. What gives¿?

[August76]

I went from a cylinder 5 misfire pulled my plug and Gap was about .06
put fresh AC Delco plugs in there then I ended up with the multiple cylinder misfire.that went away and then it was just a cylinder 5 misfire then a few times there was nothing for a while. now almost anytime the truck is idling the check engine light flashes. I checked the compression. I'm 150 psi... I'm at 5200 feet elevation so so that's pretty good.. I'm suspecting the spider injection or something else. My fuel pump was replaced last year. My engine definitely runs rough at an idle. 2 years ago it was getting the distributor code after putting the distributor in but I adjusted it until it went away that was two years ago. this misfire recently started. I guess I should also point out that I have TBI Gibson headers and the EGR valve is is not hooked up. There are no emissions where I live. the previous owner deleted the catalytic converters.
Short of replacing the spider injection system I'd like to know what's wrong first

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[east302]

Does the misfire move if you swap the number five plug with another one?

Here are the diagnostics for the P0172. Maybe it will help. There are a couple of things listed to check for besides the regulator. You’d probably need to buy the extended PIDs for your scanner app if it doesn’t show fuel trims.

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[August76]

I just paid for the extra pids. My CMP retard was off by 9 degrees I got it to .7 degrees I put a new distributor cap on also the old one didn't look too bad but I figured why not replace it so far no check engine light after adjusting the CMP retard the truck is running very smooth

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[east302]

Good deal, glad you got it running smoother. I managed to get mine to +0.4, that was about as good as I could do since it was so sensitive and such a pain to get to in the first place.

The manual says the MAF should be reading 5-7 g/s at idle. Does yours go back down at idle? Not sure if a high reading would indicate a problem that correlates to the codes you had, but it may be something to look into.


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[August76]

Good deal, glad you got it running smoother. I managed to get mine to +0.4, that was about as good as I could do since it was so sensitive and such a pain to get to in the first place.

The manual says the MAF should be reading 5-7 g/s at idle. Does yours go back down at idle? Not sure if a high reading would indicate a problem that correlates to the codes you had, but it may be something to look into.


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Yeah I had to make a lot of little adjustments. The readings seem all over

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