Any Others with the DC Sports 4-2-1 Header

Hey guys, new member here, trying to solve a problem with my 2001 accord ex 2.3 vtec. Hoping someone can help me out.

I have been getting horrible mileage for awhile now, less than 18 mpg, and haven't been able to solve the problem yet.

Ive gone through everything, replaced upstream o2 with genuine honda unit, injectors, map sensor, verified timing - right at 12 degrees at 700 rpm, throttle position sensor is fine, new ignition stuff. Fuel pressure is right on - 46 with regulator hooked up.

About the only thing I see a little weird is my downstream 02 sensor is a kick slow, but being downstream shouldnt hurt.

The only mods I have are the DC sports 4-2-1 header, injen cold air intake, and added an external ignition coild with MSD SCI ignition box.

Im wondered if any of you other guys have had issues with the dc sports header? What kind of mileage are you getting? Im wondering if moving the oxygen sensor down so close the the cat is screwing things up somehow. Sadly I sold my factory manifold and pipe so I cant test this theory.

Any ideas are appreciated!

well...i think a clogged EGR might cause low mileage..someone correct me?

knighthawk1104 said:

well...i think a clogged EGR might cause low mileage..someone correct me?

Click to expand...

It did to mine but it also made for a rough idle and threw an engine code

auto or manual?
i have dc sport ceramic 4-2-1 header and my gas mileage is still the same as the stock exhaust manifold. dirty air filter can also lead to poor gas mileage or a stuck open thermostat.

edit: also as long as the o2 sensor is b4 the cat it should be fine. mine causes no problems

EGR is a solid theory the headers shouldnt throw a code unless your 02 sensor harness is stretched out to far this happened in mine i was throwing a code cause my downstream 02 sensor wires where pulled to taught and it wasnt reading bought a denso 02 and fixed the problem

I should have mentioned that I have no codes, never have.

I did recently pull the EGR valve and clean the passageway which was pretty gunked up. It did not make a difference. Just recharged my injen filter, thermostat is pretty new. It leaked a few years back and got a code for too long to heat up. Heats up fast now.

What kind of mileage are you guys getting with the header?

Sorry forgot to mention its an automatic.

I've got a DC DAC (short ram intake) and a 4-2-1 DC header and have always gotten decend mileage (23-30 depending on who drives it, where and how much I keep my foot in it!). I used to have Greddy exhaust and went back to factory without any changes. The I/H/E was installed at around 13K miles and the car now has over 200K.

Never had a problem with my header and getting horrible gas mileage.

23 would make me very happy. I guess if you other guys are doing okay with the header that rules out a design issue.

Bought a new KN conical air filter for the CAI yesterday. Was not clogged but kinda beat up so why not.

Timing was spot on so I cant see the MSD ignition being an issue. Never had any misfires.

Only thing I can see is my downstream oxygen sensor is slow to heat up and jumps around a bit even though I installed a brand new magnaflow cat. Normally a downstream shouldnt affect the fuel trim though but im wondering if the accords used them to help control fuel delivery? The FSM ive been reading seems to suggest this.

If not Im out of ideas to try....