Hey guys,

I've got an 89 Si, w/ B16A2 converted to OBD1. When I first did the swap last summer, I was getting decent gas mileage...I remember getting 38mpg on a trip to Canada. For some reason though, in the past few months I've been getting worse and worse mileage. It's been tough to get 200 miles out of a tank, and my last fill-up, which was mainly highway miles around 70mph, and no VTEC at all during the trip was 26mpg. 1 mpg better than what I've been averaging in mixed driving (25mpg has been my avg. recently).

The car drives fine, with no codes. The exhaust does smell rich, and when I do oil changes, I can smell plenty of fuel in there. Also, when I did the swap last summer, I did a full tune-up, including fuel filter.

I've got two questions:

Could a failing fuel pressure regulator lead to rich conditions? (This was just something that came to mind)

What else would you suggest checking?

Thanks...



Modified by Its me DUB at 4:30 PM 5/27/2008

 

primary o2, but i dont know why you arent throwing a code

 

I have the same situation, b16a obdo barely 200miles per tank!

No codes but smells rich from exhaust also!

 

not sure but have you tried resetting the ecu?

 

bump, i got this too

 

Its your oxygen sensor. It's failing. Just replace it.

Janos

 

change your o2 sensor it that doesn't work ,look up the test proceudres for your Throttle position sensor and map sensor but if it isn't running bad don't worry about the map or you could have a vacum leak or a pluged line

 

is it normal, when you start your car to idle at about 1000-1500 rpm, then drop to 700 as it warms up and stay their

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Janos Lin &raquo;</TD></TR><TR><TD CLASS="quote">Its your oxygen sensor. It's failing. Just replace it.

Janos</TD></TR></TABLE>
Thanks guys...that does make sense, I just figured I'd be throwing a code. It's got the stock O2 sensor there from what I can tell...don't know if it's been changed in 19 years

I'll change that out, as well as spark plugs, because I'm sure they're probably fouled by now and see what we get.


EDIT: Should I have a 4 wire Oxygen Sensor since I'm OBD-1?? I found this link https://honda-tech.com/zerothread?id=2079699 and it lead me to believe I should have a 4-wire Oxygen Sensor. Could it have failed because I still have a 2-wire on there??


Modified by Its me DUB at 3:26 PM 5/28/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by acmoc &raquo;</TD></TR><TR><TD CLASS="quote">is it normal, when you start your car to idle at about 1000-1500 rpm, then drop to 700 as it warms up and stay their</TD></TR></TABLE>that would be normal

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Its me DUB &raquo;</TD></TR><TR><TD CLASS="quote">
Thanks guys...that does make sense, I just figured I'd be throwing a code. It's got the stock O2 sensor there from what I can tell...don't know if it's been changed in 19 years

I'll change that out, as well as spark plugs, because I'm sure they're probably fouled by now and see what we get.


EDIT: Should I have a 4 wire Oxygen Sensor since I'm OBD-1?? I found this link https://honda-tech.com/zerothread?id=2079699 and it lead me to believe I should have a 4-wire Oxygen Sensor. Could it have failed because I still have a 2-wire on there??


Modified by Its me DUB at 3:26 PM 5/28/2008</TD></TR></TABLE>

Well your ECU should throw a O2 code for the missing O2 heater circuit. But I guess since it didn't, it must be chipped, and it might be chipped to ignore most conditions which could trigger a CEL.

You defintely should be using a 4 wire O2 sensor. And depending on where your O2 sensor is located, your 2 wire may have worked occasionally. If the sensor is located close to the exhaust ports, the heat from the gases will heat it up to operating temperature. But with the newer cars, Honda moved it down nearer to the catalytic converter. With the sensor further back, the exhuaust gases would cool off below the O2 sensor's activation temperature. Without the heater it could not get to operating temperature, and clean itself. It needs to get hot enough for it to work correctly.

What kind of ECU do you have, and is it chipped?

Janos

 

Yeah my ECU is chipped. Probably why it didn't trigger the O2 sensor. So what model should I get an O2 sensor for? I also need to do a little research and how to wire it up.

 

Ok when was your ECU chipped? When you did the swap or sometime after that?

You can just use the O2 sensor from a 1992 Honda Civic EX or Si (D16Z6)

Janos

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Janos Lin &raquo;</TD></TR><TR><TD CLASS="quote">Ok when was your ECU chipped? When you did the swap or sometime after that?

You can just use the O2 sensor from a 1992 Honda Civic EX or Si (D16Z6)

Janos</TD></TR></TABLE>
Yeah I just used the ECU that was included with the engine when I bought it. When I did the swap, I had no codes and it was running fine, so I thought all was good. Thanks for the heads up...I will look into getting that model of O2 sensor.

 

If your ECU is chipped with some sort of stupid ebay-ricer-mugen chip you'll never get good gas mileage. Those things are always pig rich.

But you said you got 38mpg at the very beginning, so you may actually have a decent program in that thing.

Is the engine stumbling at all or otherwise running rough?

 

It actually runs very well. No issues other than this...

 

my obd0 b16 in my crx runs a little rich too but it has been better on gas milage and not quite a strong smell of gas in my exhaust

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redsi89 &raquo;</TD></TR><TR><TD CLASS="quote">my obd0 b16 in my crx runs a little rich too but it has been better on gas milage and not quite a strong smell of gas in my exhaust</TD></TR></TABLE>
Is it s'pose to smell like gas

 

your doing it wrong!!

 

If you can smell gas, that means a lot of unburnt hydrocarbons which means poor emissions and mileage will suffer also as its basically pissing $4 bucks of gas out the tailpipe

Should not really have a noticeable smell to the exhaust at least not gasoline. But that should be fixable depending on what the cause is, usually the O2 sensors.

Janos