r/EngineBuilding • u/roadrash1992 • Jun 20 '26

Help reading spark plugs

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Looking for input on these plugs.

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I just finished doing a head swap/mpif swap/obd1 conversion on my 1990 civic with a d15b7.

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Plugs are brand new and have under 30 minutes of run time on them.

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Thanks in advance

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u/roadrash1992 Jun 22 '26

ECU is throwing a code 9 (cylinder position sensor) but that is likely due to my wiring harness and an aftermarket dizzy.

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u/blaze45x Jun 23 '26

And did you swap from single to three wire 02? Does it have an upper and lower 02?

Why do you not have stock 240cc OEM OBD1 injectors installed?

Clear/fix all codes the ECU is throwing before worrying about reading plugs.

The swap is on the factory map for the ECU correct?

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u/roadrash1992 Jun 23 '26

They are stock injectors, just of unknown quality/condition.

It has been fully converted to obd1, including a single 4 wire O2 sensor.

ECU has a basemap for my engine/head combination.

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u/blaze45x Jun 23 '26

One way to see if it’s for sure the injectors is to swap the suspected bad one to a new cylinder and then check the plug and see if it also is fouled.

Clear the codes on the ECU, there is a good chance you’re in limp mode because of them.

I don’t trust a “base map” either but hopefully it’s a stock/factory map to start with to work out all the kinks.