Lower O2 sensor on a '98 Civic EX coupe.

changing the exhaust system can alter the gas flow and may create problems for the sensors . The HO2s sensor and the O2 sensor may now be operation on the edge of the parameter settings and any exhaust coating on the sensors may be affecting their performance. Run fault codes to check the sensors and sometimes removing them and cleaning them in vinegar to remove the coating will improve the situation. What ever is the problem if it started after the manifold change then that is the area in which to seek answers.

Air filter, ECU, O2 sensor, bad EGR valve, or clogged cat converter.

Onboard diagnostic computer should be throwing codes. Autozone can check these free (as will other part stores).

It is on the lower left side of the engine (side towards firewall - see picture).
Knock sensor failures are pretty rare, why are you looking for it?

If the coil is good and giving out spark and your ICM is good the cap can have a missing button which will not allow spark to go to the spark plugs through the plug wires do replace the distributor cap and rotor and spark plug wires

the one at the bottom of the exhaust manifold as shown in below picture.

This pic MIGHT be helpful (it's from a 98):


Hope that it helps. If not leave a comment and I will try to find something else.

have your charging system checked, you may have a bad Altenator

could be your lower O2 sensor

i had a similar problem.......try changing out the starter...because on mine the starter solenoid was bad...thats what engages the starter...the starter and the solenoid is all one part..

remove rear seat, remove round metal cover, disconnect fuel lines and wires from top of fuel pump, jack up rear of car. remove gas tank straps, lower gas tank with a jack, install is reverse.....if you need to just replace the fuel pump you don't have to remove tank you Can access from under rear seat good luck and please rate -jeff