I changed plugs a couple weeks ago to BPR8EIX. I pulled them a week later to change the gap and noticed that 1 was not blackish/brown like the others. Didnt think much of it, regapped and reinstalled. Today I pulled them to change the gap again and its the same. Thinking oh no..leaking head gasket is cleaning this cylinder, I did a compression test. Results were 155-168. The 168 is the clean plug.... Shined a light down in each cylinder, all pistons look the same...black. Motor has 110k on it. Im planning to replace the HG this winter as well as a few more things. No sign of cloudy oil, no sign of oil in coolant. Id love to think I can keep beating on this thing for the rest of the summer before the minor top end rebuild planned this winter. Suggestions?

 

valve seals?

 

Doubtful. I think the black ones are normal. The clean one is suspect.

 

I suppose it is on cylinder number 1. My guess is simply because it is the first cylinder that is getting air and probabably run a little leaner than the other cylinders.

 

#3 All three others are exactly the same. Just #3 is clean as a whistle.

 

swap the #3 injector to another cylinder to see if that is the issue. If the issue follows it then replace it.

 

What would other symptoms of 1 bad injector be? Is there anything loggable that I can look for?

I guess it should also be noted that both times I pulled them and saw this was after 1st start in the morning idling in driveway.

Im starting the think that maybe the other 3 are dry fouled. Here is a pic. Some of the "scratches" on the black ones are me scraping with my fingernail to see how thick the soot was. Opinions?

Im probably just going to toss them back in. And while finishing my tune I'll log coolant temp and watch for spikes during pulls. This winter will see cams, inj, porting, and new gaskets. Im just hoping to keep driving it for a couple months.

 

knock count would be up a little if one is not good. AFR may be being compensated for by the ECU to compensate for the slightly lean condition causing the other three to be slightly rich. The three are normal looking, the clean one is indicating a real problem.

I just thought of something, you might check the harness to see if that one injector isnt being fired..

Other than that , just replace the one injector or send them out to RC Engineering to have the full set cleaned.

I would figure out the issue before you starting doing any building...before it goes boom

 

Swapped #3 and #4 coil packs and put some inj cleaner in the tank. Im going to run it for a few days, and recheck plugs again. If the issue moves to #4, its the coil. If it is gone, the inj cleaner worked. If it stays in #3, I'll swap the #3 injector to #4.

Ive been tuning SD fairly extensively lately in open loop. So if it is an injector it wouldnt compensate, but I sure have.

 

Sounds like a plan