These are the symptoms...

1)Lack of power
2)Bad gas mileage
3)Black spark plugs

My lude has intake and exhaust w/ 35k. Right now I am running NGK's w/ 8.5mm Magnecore plug wires. I use Mobil 1 10W30 and I am on top of things when it comes to preventative maintenence. I used to get around 300K to the tank. Recently I have been getting around 200K to the tank and my car seems much more sluggish. My lude has not been my daily driver, so I have been working on finishing upgrading my suspension and brakes. I rarely drove it. But now, I want it to be my daily driver, but it isn't running tiptop. My spark plugs are black at the tips like I am running rich. I recently changed the fuel filter, pcv valve, and k&n filter. I think it might be a timing problem, but my buddy thinks it is something else. Any suggestions would be greatly appreciated.

 

what mods on the car?

how many tanks have you run through her since you started to drive her again?

 

Check your O2 sensor. Having a bad one will mess up your air/fuel ratio.

 

I did a search and found this
https://honda-tech.com/zerothread?id=962209

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Shakes &raquo;</TD></TR><TR><TD CLASS="quote">what mods on the car?

how many tanks have you run through her since you started to drive her again?</TD></TR></TABLE>

The only mods that I have that would affect anything are intake and exhaust. I have probably ran about 3 or 4 tanks driving her as a daily driver. When I bought my lude w/ 34K, I probably only ran through 4 or 5 tanks the whole time it sat in my driveway, which was over a year. Would an O2 sensor go bad after 35K? I will definetly check that out though. By the way, I have no CELs.

 

I would imagine it is not to common but it could happen. My car suffers from some of the same symptoms and that is a problem I have. Next pay check I'm going to replace mine, I think they are only like $80. When my car really starts to run all messed up and throws a code that is the code I get. I am running an 02 sensor from a S model on my H22 and I am not sure they are exactly the same.

ProjectPenny, you should try resetting your ECU and see if that helps anything. Check for codes too, My check engine light did not come on all of the time but it still threw the O2 sensor code.

 

This might seem like a silly suggestion, but... get new NGK Copper Plugs. And check to see if both ends of your plug wires are nice and secure.

 

also you said the plugs are black? is there any oil on them? if so, thread side or connection side. do a compression test if there is, oil in the chamber will kill power

 

Man, you are getting less than 300 miles to a tank?? I average 380-400 miles on my 92 Si.

Do you drive your car hard??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AndyD &raquo;</TD></TR><TR><TD CLASS="quote">Man, you are getting less than 300 miles to a tank?? I average 380-400 miles on my 92 Si.

Do you drive your car hard??</TD></TR></TABLE>

i think 300 is pretty normal...at least it is for me

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AndyD &raquo;</TD></TR><TR><TD CLASS="quote">Man, you are getting less than 300 miles to a tank?? </TD></TR></TABLE>

thats what i normally get.... best ever was around 350 and that was highway driving with the cruise on the whole time

 

Lack of power and bad gas mileage would lead me to a bad cat at first..but the black plugs and I have no idea.

 

I'm not sure how O2 sensors normally fail(gradually or all at once), so this is just a guess.....

Perhaps the O2 sensor is failing and returning a lower voltage than normal(but enough to avoid a cell), causing the ECU to read it as lean, inturn running the engine rich(black plugs)???

Like I said....just a guess, but it seems feasible to me.

 

Thanks everybody for the suggestions . I am going to look at it today at work. The plugs are black on the ground electrode side, not the thread side. I will definetly be checking for codes and the 02 sensors. I'll post back w/ what the problem was.