This is driving me crazy, I have a 1993 civic Si with 105000 Kms.
For about the last 8 months the car has been running rich and popping and missing at idle. Most people dont notice but its my car I know its not right. Im sure this is not oil consumption and my compression is good. New plugs rotor cap and coil. Idle is more rough than usual, there is a large buildup of black soot around the tailpipe. Im kinda annoyed and I have checked the timing, I have also had the valves adjusted. Just had my timing belt done (after the problem started) Im freaking out. No CEL either.... What could it be???
Help!
Steve

 

If this makes a diff. I have a short ram intake and also have a header, its a fairly simple stock setup. Thanks
Steve

 

You never said you changed the wires. Have you?


Edit: and are the plugs gapped correctly?

 

What kinda oil you use?, what header and is their a proper bung hole for the right o2 sensor?. Did you possible burn out you're O2 sensor from the aftermarket header and you're just running rich because of that?, get a new o2 sensor. If thats not it is you're timing advance a little, either way sounds like you should get some iridiums like i had too just yesterday, cost 55$ for the four of them but they sure as hell fire like they are suppose to now that taking into consideration im running pretty rich my self on a d15b8, pfft ha...

 

Could be the fuel pressure regulator I think.

 

I did not change the plug wires, I did test the resistance. Its just a regular 421 header. I think that its possible the o2 sensor but with no CEL im worried. ANyone have an o2 sensor make the car run so rich without a CEL???
Steve

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s_vares &raquo;</TD></TR><TR><TD CLASS="quote">I did not change the plug wires, I did test the resistance. Its just a regular 421 header. I think that its possible the o2 sensor but with no CEL im worried. ANyone have an o2 sensor make the car run so rich without a CEL???
Steve</TD></TR></TABLE>

your o2 can definitely make you run rich before you get a cel. I bet this is your problem, unless you have changed anything else in the fuel system (fuel pump for instance).

 

Could be many things, you need to diagnose the problem or take it to a shop and have it diagnosed, otherwise you'll just be throwing parts at it.

Running rich can be caused by a bad O2 sensor, MAP sensor, or ECT Sensor. Seeing black carbon/soot buildup on the tailpipe is a bad way to diagnose a rich condition however, as buildup there is pretty normal. I'd work on fixing the miss at idle, then see if you're running rich or not.

 

u said this happened right after u did the timing belt... is the belt off a tooth?? check out the timing

 

Timing belt is good, fuel prssure is good, timing is BANG on.... no cel

 

maybe a bat catalytic converter??
that was just off the top of my head.

and exactly what all mods to you have?

 

I have no cat, Header, Short ram, lowering springs, thants all.

 

HAHA atlast, this is STUPID i found the problem... well sorta, I disconnceted my air fuel guage and it runs much better. Beens like even with the wire off and taped up the guage still shows between lean and stoch. STrange i guess either the guage is bad or my wire is shorted or grounded out somewhere.... Hrmmmm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s_vares &raquo;</TD></TR><TR><TD CLASS="quote">HAHA atlast, this is STUPID i found the problem... well sorta, I disconnceted my air fuel guage and it runs much better. Beens like even with the wire off and taped up the guage still shows between lean and stoch. STrange i guess either the guage is bad or my wire is shorted or grounded out somewhere.... Hrmmmm</TD></TR></TABLE>

did you solder the guage in? if you don't solder your wires, your connections can change the signal the ecu sees. Glad you figured it out though.