i drive a 98 civic dx and i get really bad gas mileage. i have changed airfilter, plugs, wires, rotor button, cap, fuel filter, cleaned my iacv and ajusted my valves. i removed the cat b/c i had a crack in my stock manifold and put an after market DC one in its place. i have no cells it just gets crap for gas mileage. i get about 230 a tank. what else could i be missing. i also have a rough idle problem. idles around 600rpm and 800rpm. i have searced and i have found no other solution to my problem. i am open for any kind of sugestions. thanks

 

How many miles on it? If over 100k try a new primary O2 sensor

 

do you get any bogging?

 

i have 120,XXX on the motor

and yes i get bogging. what would cause that?

 

get a compression or leakdown test yet? Any oil spillage/seepage from between the block/head?

 

thats the two things i have not done yet.. i will run a compression test tonight to see where that stands. i will have to search on how to do a leak down test. i have never done one. when you say oil between the head and the block? head gasket? or just rings are prob. gone? any thing else i should check tonight while i check comp. i did notice that i am burning or leaking oil some wear. the car does not smoke when i drive it or rev it up. and the motor is clean for the most part.

as far as the 2nd o2, would that not cause a cell if it was bad? if not how would i test it?

 

yes the o2 would cause a CEL almost immediatly

Oil between the head and block are signs for headgasket. If you're loosing oil or burning it that could lead to other problems as well.

 

compression test WOT and motor was normal operational temp. showed me 170-165-170-175 its not that good. but should i be burning oil? still need to find a shop to do a leak down test on my car. i don't have 200+ bucks to spend on one from snap on.

number 3 cylinder was kind of low. but i guess its still in spec.

i had my frined follow me last night and i ran my car to 7200rpm on the highway and he told me im blowing alittle smoke out of my exhaust when i get to a high rpm. i could see it kinda when i looked in my rear view. if its not my rings causing it, maybe my valve seals are?

 

bump

 

k swap ftw!