2002 Civic ex Misfiring

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,721
Points
63
Location
St-Hyacinthe, Quebec, Canada
Ok, plz disregard half of what I just wrote. For some reason, I forgot this was a year change, and they went to coil on plug. The accord stayed dizzy till 2002, the civic was a 1.7l seven gen. Sorry, but the rest still applies, live data and etc.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,721
Points
63
Location
St-Hyacinthe, Quebec, Canada
You mean you 'removed' the O2 sensor and it smoothed out? If so, the exhaust is restricted.
But I think he just wrote he unplugged it. But that is a very astute comment, he could do a backpressure test to confirm.

There is a way to do that with live data and a scope. But that is a bit beyond the regular car guy. But being educated is key. I found this video, which is in all intents for educational purposes. But again, GRC is on the ball. ;)

This video is long, but well worth the effort to listen to. @GRC, he is using an autel scope. :mad:

 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,659
Points
48
The OP has not mentioned any power loss while driving, only a rough idle and the codes; is that correct? I'm guessing a plugged cat would show up as power loss long before the idle was noticeably affected. That manifold crack seems likely, throwing the fuel trims off and causing misfire as well as cat codes. If it is cracked, figure on replacing it if you want it to be more than a temporary fix.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,721
Points
63
Location
St-Hyacinthe, Quebec, Canada
Yet again, idle will sometimes fool you, bet when you open WOT, everything goes south.

This is where you need charge readings. What percentage are you at in TIME of load?
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,721
Points
63
Location
St-Hyacinthe, Quebec, Canada
Huge correlations to be seen here, and live data never lies if it is quick enough. If op has a scan tool that can see this, a volumetric equation should suffice to gett sensible data, but he states the 4 bangor is stable on compression, so the engine is in principle, able to BREATH, now we just need to know why it is not reading right, and misfiring.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
10,721
Points
63
Location
St-Hyacinthe, Quebec, Canada
doing a static compression would be viable here, and a very usefull tool to gander at, it relys on amp draw from starter, way more reliable than physical compression check as it, but again, I am getting way ahead of where we should be.

BTW, @billr, my sister is recovering very well. Miracle so to speak. Thx, you helped me in a big on that one while you calmed me down. I kept your e mail, refer to it when my man cave brain thinks better of my ego.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,659
Points
48
Since you pointed out that these engines are prone to cracking the exhaust manifold, that is what I would check immediately. Checking for a crack should be quick/easy to do, and a crack there right above the primary O2 sensor could have a great effect on fueling
 
Top