whats up everyone, since i have owned my 92vx its had a bad 02 sensor, but i was getting 38mpg anyways. so last week i change the o2 and now im getting 31mpg and a miss at low throttle. im stumped, everything is new tune up wise. and only 100k on the motor. do you think i could have the cam timing 1tooth off causing this???

 

check the timing on both the belt and the dissy

do you have and CEL?

did you reset the ecu?

Is the O2 sensor OEM?

 

Wrong O2. The VX uses a different O2 than the other Civics, and it's more rare to find.

PS. I'm getting 28 street, 40 highway on my 93 DX with a SOHC VTEC automatic.

 

Damn I get 31 in my b16 cx. I would make sure you get an OEM VX O2, that's your problem.

 

yeah definetly need a 5 wire o2 sensor.
If u bought a new o2 at autozone, they will lie and say its for the VX, but if its under $200, then it isnt.

 

im not that retarded comon. i have a oem 5wire. there was a code for the o2 before i swapped it, but it ran fine. now with the new o2 the mileage has dropped and i have no codes, and i get a pretty constant miss at low throttle/high load. everything tune up wise is new, so i dont have a clue whats going on.

 

oh, and yes the ecu was reset, and yes its an oem o2 sensor. the expensive one. i have a friend with a 95vx and his was doing the same thing, and he put plugs in it and says it good now, but my plugs are new NGKs. and the problem with the miss wasnt there until i replaced the o2.

 

Hmm... this is weird. Not really sure what your VX's problem is then.

Even my GSR swapped hatch gets 35-36 mpg and 30-31 mpg in the winter due to letting it idle like 10-15 minutes total each day to warm it up.

 

yeah, its a bummer, buy the crappiest civic hatch to get good mileage until a swap, and dont get near what it should. i got a hybrid tranny in the back waiting to go in, but i dont wanna drop the mileage anymore, or change any factors until i figure out this problem.

 

I also have a Vx but im getting 25mpg, WTF?!?!?

 

word, we gotta keep bumping this until we figure it out.

 

does it miss at idle also?

 

well my exhuast pudders

 

With basic mechanical knowledge both of you could solve your respective problems.

Have you looked at your spark plugs?
Have you checked your timing?
Do you have any CEL's?

 

sorry LSVTEC but i am ASE certified and was actually a "driveability tech" for a few years. but to answer your questions read above post. NO CEL anymore with the o2 replaced. spark plugs looked perfect after 40k miles, but replaced with NGKs a month ago or so, looked at them today and still new light brown at the most, ignition timing is right on, not 100% sure about valve timing, could possibly 1 tooth off on the cam, but still wouldnt make sense why it run fine before the new OEM o2 and get better MPG with a bad o2???? so, this is why im stumped. my next guess is a bad EGR valve, sticking or clogged. causing the rich condition. im gonna bypass the vacuum source to it tomorrow and see how it reacts during normal driving.

 

check your egr, to see if there is some port clogging. that's a major cause of low throttle position runnability.
also check cam timing. an old belt, combined with a worn tensioner can actually cause the cam to jump a tooth. i've seen it before.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">sorry LSVTEC but i am ASE certified and was actually a "driveability tech" for a few years. </TD></TR></TABLE>

Well, not to be an ***, but im glad i didnt ever have to take a car to you if you cant solve a simple fuel consumption problem with your own Honda.

 

well i will figure it out, its just that i am used to OBD2 and a snap on computer. if it wasnt a VX with the complex lean-burn and 5wire it wouldnt have been nothing to figure out. but this is a new game to me. thanks for all the help everyone.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">well i will figure it out, its just that i am used to OBD2 and a snap on computer. if it wasnt a VX with the complex lean-burn and 5wire it wouldnt have been nothing to figure out. but this is a new game to me. thanks for all the help everyone.</TD></TR></TABLE>

OBD2 is essentially the same as OBD1 save for extra codes, permanent and temporary DTC's and some other little stuff. What snap on computer were you using?

 

i dont remember exactly what model # it was, its been a few years since i have used it. the major differance now is that i dont have the scanner to view all the parameters at once, so im having to check every sensor manually (dvom) and them compare it to the specs instead of just watching the sensors on a screen or a square wave and looking for a glitch.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mike K &raquo;</TD></TR><TR><TD CLASS="quote">check your egr, to see if there is some port clogging. that's a major cause of low throttle position runnability.
also check cam timing. an old belt, combined with a worn tensioner can actually cause the cam to jump a tooth. i've seen it before.</TD></TR></TABLE>

 

checked the egr out today, no luck. im beginning to think it has something to do with the shortram intake, header, or catback. maybe the bad o2 just had it in limp mode so long that i didnt know the mods where affecting the a/f. also advanced the timing and no luck, actually seemed worse.

 

if your ignition timing is correct then your cam timing is correct. you can't have one or the other. you'd think a ASE certified tech would know this.

BTW, b2 bottom end with 300k+ (smokes like a bitch), 92 cx head, y8 trans, 4-1 header, test pipe,catback exhaust, 1 wire o2 with stock intake manifold and ecu, no idea where ign timing is at= 31.25 mpg city with a/c and pulling trailer at times.

 

i know if the ignition timing is on then valve timing is on. what i should have said is when the motor was swapped the ignition timing was set, but a year later when i did the timing belt/water pump i might have got the cam off by a tooth. i havent checked the ignition timing since the timing belt change. sorry, should have made that clearer.

 

just want to thank everyone trying to help, i know you could easily just not reply at all. im so pissed about this i cant think straight. as of now what has been checked is; egr valve, tps, plugs, wires, dizzy cap, rotor, inj clean, new o2, and advance ignition timing (without a light) and all yield no fix. i threw the old o2 on just for ***** and giggles, and it ran perfect, but then got the CEL and erratic idle. new o2 back in and same miss/rich condition.