93 Honda Civic Mileage gone bad

How do you know this isn't the way it's supposed to work?

If you google on the internet and examine a cut-away, it's
far more than a check valve.

Suit yourself. I saw your other post and see you're now
dealing with a bigger problem. I'd be checking the coil.

 

How do you know this isn't the way it's supposed to work?

If you google on the internet and examine a cut-away, it's
far more than a check valve.

Suit yourself. I saw your other post and see you're now
dealing with a bigger problem. I'd be checking the coil.

 

I've never found a reliable way of testing them. I clean the bejeebers out
of them with carb cleaner (some don't survive parts dip) if I don't have any
place to buy a replacement at the time. They normally shouldn't close all
the way, although they can close at wide open throttle or when you are
holding it in your hand. At idle, they should allow some bypass to scavenge
the small amount of blow-by. At cruise throttle, they should open to
scavenge the increased amount of blow-by. Your old one may be defective - it
sounds like the spring has become weak. Normally you should feel quite a bit
of resistance (the proper direction, blowing from the engine end) at
pressures we puny humans can produce.

Mike

 

I've never found a reliable way of testing them. I clean the bejeebers out
of them with carb cleaner (some don't survive parts dip) if I don't have any
place to buy a replacement at the time. They normally shouldn't close all
the way, although they can close at wide open throttle or when you are
holding it in your hand. At idle, they should allow some bypass to scavenge
the small amount of blow-by. At cruise throttle, they should open to
scavenge the increased amount of blow-by. Your old one may be defective - it
sounds like the spring has become weak. Normally you should feel quite a bit
of resistance (the proper direction, blowing from the engine end) at
pressures we puny humans can produce.

Mike

 

Sadly, it's very possible. Honda spark coils are not very tolerant of being
fired up without a load. My son zapped his coil just using the starter to
"bump" the distributor to the proper position. The result can be seen at
http://tegger.com/hondafaq/badsecondary/internal-arcing.html D'oh!

The initial problem sounds like a bad "main relay" - see
http://tegger.com/hondafaq/faq.html#startrun for the straight scoop on that.

Mike

 

Sadly, it's very possible. Honda spark coils are not very tolerant of being
fired up without a load. My son zapped his coil just using the starter to
"bump" the distributor to the proper position. The result can be seen at
http://tegger.com/hondafaq/badsecondary/internal-arcing.html D'oh!

The initial problem sounds like a bad "main relay" - see
http://tegger.com/hondafaq/faq.html#startrun for the straight scoop on that.

Mike

 

oxygenated gas. used in many parts of california from (IIRC) nov thru march.

 

oxygenated gas. used in many parts of california from (IIRC) nov thru march.

 

That is a classic pass/fail test for O2 sensors, but most sensors fail by
becoming more and more sluggish - degrading over time. When new, they should
produce over 7 transitions per second as the output drives the mixture back
and forth past the ideal point. As the sensor ages, the response rate drops
until the ECU will no longer tolerate it and you get the "check engine"
light. As another recently reported here, replacing an old O2 sensor can
improve throttle response even if the reaction time of the old one was not
causing the ECU to complain. The ECU must also adjust the mixture at a rate
that is independent of the condition of the O2 sensor (because it has no
direct knowledge of the sensor's condition), so the mixture will fluctuate
more in proportion to the sluggishness of the sensor.

IMHO the "sweet spot" in the car's life for replacing the O2 sensor is
around the half-way mark, or between 100K and 150K miles. I doubt many O2
sensors last the life of good modern cars, so we can all expect to replace
the sensor once (whether the little light comes on or not). If we are going
to remove the sensor for testing because we suspect it, I suggest the best
thing to do is put in a new one and be done with it.

Mike

 

That is a classic pass/fail test for O2 sensors, but most sensors fail by
becoming more and more sluggish - degrading over time. When new, they should
produce over 7 transitions per second as the output drives the mixture back
and forth past the ideal point. As the sensor ages, the response rate drops
until the ECU will no longer tolerate it and you get the "check engine"
light. As another recently reported here, replacing an old O2 sensor can
improve throttle response even if the reaction time of the old one was not
causing the ECU to complain. The ECU must also adjust the mixture at a rate
that is independent of the condition of the O2 sensor (because it has no
direct knowledge of the sensor's condition), so the mixture will fluctuate
more in proportion to the sluggishness of the sensor.

IMHO the "sweet spot" in the car's life for replacing the O2 sensor is
around the half-way mark, or between 100K and 150K miles. I doubt many O2
sensors last the life of good modern cars, so we can all expect to replace
the sensor once (whether the little light comes on or not). If we are going
to remove the sensor for testing because we suspect it, I suggest the best
thing to do is put in a new one and be done with it.

Mike

 

Question;use a OEM Honda/Acura O2 sensor,or will a 3rd party sensor
suffice? (at a lower price)

 

Elle found a place to get OEM on-line at a nice price for early models. I
thought I saved the link but maybe she'll see our plight and repost it.

Mike

 

You are right. The secondary coil shorted someplace and is now only
half the resistance it should be.

I'll post the best price when I find it.

 

You are right. The secondary coil shorted someplace and is now only
half the resistance it should be.

I'll post the best price when I find it.

 

I purchased an Ignition Coil online at

http://www.thepartsbin.com/

$46.50
+ Distributor O-Ring ($3)
+ some random $1 thing to push me over the $50 free shipping mark.

 

I purchased an Ignition Coil online at

http://www.thepartsbin.com/

$46.50
+ Distributor O-Ring ($3)
+ some random $1 thing to push me over the $50 free shipping mark.

 

Thanks for the link!

Mike

 

Thanks for the link!

Mike

 

done with it.

and repost it.

https://www.automedicsupply.com/

I bought one for my 91 Civic from these folks about a
year-and-a-half ago. Good service. No problems. I think
their prices are competitive for more recent models, too.

From my reading on the net last year, people say to only buy
OEM. Aftermarket are not as reliable.

For the original poster: Check that timing! I monkeyed with
mine a bit a month ago, and I think it's why my mileage
dropped a bit below 40 mpg on the last three tanks. So darn
hard to see the timing marks lined up, especially with
middle aged eyes. Or I didn't let the car warm up enough.

 

shipping mark.

After market, hmm. Let the group know how it goes. I'm
afraid the aftermarket coils I've had did not last nearly as
long as the original, OEM one.

Way to troubleshoot!