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Today I was doing a second gear pull and at about 6000 I had a huge hesitation as if I had let off the gas and a huge pop/backfire. My power band has also been acting really funky lately, the car feels like it goes in and out of power almost. I pulled my spark plugs to check the overall health and I'll be compression testing soon, just waiting on my buddy to head over with the tester.

Any opinions or thoughts on what I should check out first? I'm thinking it has something to do with fuel as I run into more problems on a low fuel tank.

It seems like there might be oil on the threads of the spark plugs? The previous owner had a compression test done about 1 year and 7 months ago, I've included pictures of the test and all of the plugs. 

I'm still running the stock injectors and I don't know when the fuel filter was last replaced. Spark plug is a BCPR7EIX.

Mods-

HKS Downpipe

Catback Exhaust

Apexi Intake

Splitfire Coils

Tomei Fuel Pump

New WS coil pack harness

Re-soldered and cleaned MAF Sensors

 

 

 

 

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2 photos are a little darker on the insulator than the others. That would tend to suggest that if there's any fueling issue, it's not across the whole engine (ie, not necessarily related to the pump or tank level). Maybe the pale ones are all lean and somehow the dark ones are not....but that's a stretch.

Anyway, It's not caused by the plugs. They all look fine enough. The darker plugs may be being caused by the coils on those (that?) plug being weak.

You can't guess this stuff though. The smart move is to put a fuel pressure gauge onto it and run it under load to see what the pump is doing. Wideband up the tail pipe at the same time will help. Knock ears on at the same time will also be good.

You can get it nice and hot on a dyno to see if it happens only when warm enough.

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47 minutes ago, GTSBoy said:

2 photos are a little darker on the insulator than the others. That would tend to suggest that if there's any fueling issue, it's not across the whole engine (ie, not necessarily related to the pump or tank level). Maybe the pale ones are all lean and somehow the dark ones are not....but that's a stretch.

Anyway, It's not caused by the plugs. They all look fine enough. The darker plugs may be being caused by the coils on those (that?) plug being weak.

You can't guess this stuff though. The smart move is to put a fuel pressure gauge onto it and run it under load to see what the pump is doing. Wideband up the tail pipe at the same time will help. Knock ears on at the same time will also be good.

You can get it nice and hot on a dyno to see if it happens only when warm enough.

I accidentally uploaded the same picture twice, its just cylinder # 4 that is dark like that on one side. All of the rest seem to be the same with slight color on them.

So its probably an injector issue at high load? I'm afraid that it is an issue of my engine leaning out because I have my downpipe, exhaust and intakes on without a tune. Also my o2 sensor on my cat was chopped by the previous owner.

I just don't understand how it could be the coils or the fuel pump when I just replaced them

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Well, we didn't know that the coils and pump were new....

Given that, they are less likely to be causing your problem. Running without O2 feedback is definitely a problem unless you are under high load all the time. It will cruise on O2 feedback, and if it doesn't have it, the mixtures could just be lean enough to whiten the plugs. But, that won't cause a miss at 6000 under load.

And, you really really should not be leaning on an engine that has had breathing mods etc, without having it tuned**. Just asking for trouble. And given that, the number of possible causes for your shenanigans goes up by a large number. Put it on a dyno. Even if not for the tune, at least to try to fault find in a controlled environment.

 

**I will stipulate that your mods are not all that extreme and many cars have had mods just like that without a tune because it's not like you've ported it and put cams in and wound the boost up to 11ty. Just sayin', mods + no tune + misbehaviour is not an unexpected combination.

Edited by GTSBoy

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Why are you running BPR 7 ?  Would have thought 6 would be better on stock boost. Don't know if that is your problem though.

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Random internet guesses aren't going to help you here. Get it on a a dyno or at least get a wideband.

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