reading codes on 93 Civic 1.5

My 93 Civic runs, but not quite right. When under acceleration, the
engine starts to run roughly. When the car's speed catches up to the
gas pedal position, it starts to run smoothly again. Shifting into a
higher gear and pushing the gas pedal causes rough running again, until
the car finally reaches cruising speed. When faced with a slight
incline that requires pushing the gas pedal, the rough running returns.

It occurs to me that this seems like a manifold pressure problem because
it corresponds to the gas pedal/speed ratio. The check engine light is
not lit. I used to read codes on my 89 Accord by looking at the light
on the computer under the driver's seat, but I don't see a computer
under the seat in this car. I can't find anything that looks like a
scanner terminal, either.

This problem came on suddenly a couple of days ago when the weather went
from 60 to about 15 degrees in a few hours. We parked the car in warm
weather, and it no longer worked correctly in cold weather. Today it's
65 again, and it still isn't right.

By the way, I unplugged the MAP sensor and started the car, and it ran
like crap. So if the MAP sensor is bad, at least it's better than no
MAP sensor. The first thing I did was change the fuel filter. It
didn't fix the car, but it was due anyway.

The only other thing I can think of that might cause such a problem is
the oxygen sensor. Is there a way to check these components
individually, or do I just need to figure out how to read codes? The
engine light isn't on anyway, so what should I do if I don't get any codes?

 

1. reconnect the map sensor.
2. check the ignition system - replace the plugs, leads and distributor
cap is they're old.
3. say whether this is an automatic - clogged egr systems can give
similar symptoms.

 

I did that immediately, of course.

I regapped the plugs and replaced the cap and rotor. Still have same
wires. Could bad spark plug wires cause such a sudden and intermittent
problem?

Manual transmission.

 

absolutely. and re-gapping is a waste of time - it doesn't address
electrical leakage as plugs age. ordinary plugs are only ~$2.50 each
[use only ngk or denso] - simply replace. use a quality plug like
iridium if you want best performance/economy - they're $10 each or less.

 

After tuning up the car (as Jim said, new wires, plugs,
distributor cap and rotor, OEM only--they pay for
themselves--and check timing), next I'd consider replacing
the O2 sensor. Worst case this will be pre-emptive,
especially on a car this old. You can buy an OEM O2 sensor
for a lot less than what OEM online parts dealers want at
https://www.automedicsupply.com/ . I used the latter for a
new O2 sensor for my 91 Civic. Works great. The store
shipped quickly.

A bad O2 sensor will not necessarily set a code on the 93
Civic.

Suspect next a clogged catalytic converter. Then the
question is why it became clogged.

Make sure the cooling system is topped off, too.

 

Thanks for the tip. I'll look for my part there. It appears to be the
more economical one-wire type, so I'm not too scared to buy one.

That leaves just the new plugs and wires.

Thanks for the info. By the way, how do you read codes on this car? Do
you have to get a Honda-specific scanner? Where is the connector? If
you guys are right I won't need it this time, but I wouldn't mind knowing.

The coolant looked good at the last oil change about 3 weeks ago. I
noticed when I bought this car last summer that it didn't appear to have
a catalytic converter. But I just went out and looked again and I see
something vaguely converter-like just under the exhaust manifold in
front of the engine. Is that where they hid it, or is that something
else?

I'll go ahead and finish the tuneup tomorrow and let you know how it
runs after that.

 

<SNIP>

You may just have _one bad tank_ of gas. Do you run injector cleaner
through it seasonally? I almost ditched a car when it suddenly went bad
and I couldn't find the trouble. It was BAD GAS.

'Curly'

 

Yeah, I thought of that one, too. It was down to about a quarter tank
when it went bad, and I filled it up at a BP station, but no change.

 

I am pretty sure it's like my 91 Civic: Codes are read
directly at the ECU via blinking flashing lights. See
http://media.honda.co.uk/car/owner/media/manuals/ConcertoManual/62sk301/6-74.pdf
for help. It's not difficult. No special scanner or other
tool is required.

The ECU is located under the front passenger footwell mat.

 

That's a funny place to put it.

I haven't bothered to get a shop manual for this car yet, because I've
never had any trouble with it. It's a great car. Everything is laid
out so conveniently I didn't even need to look at a book when I changed
the timing belt and water pump at 100,000 miles. It took me about an
hour. I really love this car.

Thanks for the info.

 

I can't do these in an hour, but I do them handily,
leisurely and carefully within about two days (subsequent to
many tips from this newsgroup and a good manual).

I get a kick out of maintaining my 91 Civic as well. It's a
huge reason why I do not go out and buy a new one or a more
recent used one.

 

We have had this car for about 8 months, and have had dozens of people
offering to buy it. I always wonder why manufacturers stop making such
successful designs. If they were to make this car again without
changing anything, they'd sell thousands of them. I'm not impressed
with the newer cars. Big stupid wheels on a stupidly tall car, less gas
mileage, and way to ostentatious. Ditto for my brother in law's new
Camry. It just looks ridiculous next to his ten year old Camry.

 

I agree. I've got a 92 and a 93 for my wife. It sounds like we have
the same problem. I just started a thread yesterday and just now
flipped back and found yours. If you get yours solved, let me know.
FYI, grab a Haynes for $20. It's not perfect but will get you thru
most things, like checking codes. (jump the small 2 pin connecter
under your glove box, right side, pull it out of the green rubber
case, then watch CEL flash)

By the way, I also had an 89 Accord a few years back. Ran it to
450,000 km and drove it to the wrecker.

 

My 89 accord had 275,000 miles, and then it was stolen.

 

My '87 Integra had 750 miles, and then it was stolen (I'd owned it 2
weeks).