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'97 Civic Fuel Economy Drop Troubleshooting


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NikoW
New User

Apr 30, 2013, 3:03 PM

Post #1 of 6 (1100 views)
'97 Civic Fuel Economy Drop Troubleshooting Sign In

Hello everyone!

I have:
Check engine light (turned off recently after an oil change and then returned)
Code p0118
Code p0420, slightly bubbling radiator (It has only been bubbling for 2 days, when I added coolant. Before that, it never visibly let out steam.)
A recent big increase in fuel consumption and high idle (went from 500km a tank to 350km...)

I was wondering if anyone could help me troubleshoot what the problem might be (whether it's one problem or more).

I really appreciate the help!

Niko


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Apr 30, 2013, 3:11 PM

Post #2 of 6 (1096 views)
Re: '97 Civic Fuel Economy Drop Troubleshooting Sign In

You have a problem with your Coolant temp sensor and a bad catalytic converter.

The sensor itself could be bad or it could be a problem with the wiring. It needs to be troubleshooted with a scan tool and DVOM.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



NikoW
New User

May 2, 2013, 8:34 AM

Post #3 of 6 (1015 views)
Re: '97 Civic Fuel Economy Drop Troubleshooting Sign In

Thanks a lot Hammer! I have a couple follow-up questions if you're not too busy

1. Could the 0118 be causing problems with the catalytic converter? I'm thinking that these two issues are probably not related.

2. I was reading about the problems the 0118 can cause, and it said that fuel consumption can go up. What's the logic there? How does the cooling system affect the efficiency of the engine? (I only topped off the radiator fluid once in the past year, mostly because the temp sensor in the car has never moved out of the normal range. Then again, that might be because the coolant temp sensor is broken...) I think learning how these two are related will be very beneficial!

3. I forgot to add that the car burns a quart of oil every 5-6 fillups. It is not dripping the oil, so it must be burning it (no smoke in the exhaust, but it does smell like it's running rich). What do you think of adding one of those stop leak additives to the engine oil?

Thanks so much!!!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 2, 2013, 9:31 AM

Post #4 of 6 (1012 views)
Re: '97 Civic Fuel Economy Drop Troubleshooting Sign In

Sure, both the oil and excess fuel being burned will ruin a cat. A temp sensor reading too cold will feed way too much fuel and if it's open circuit, it will be telling the computer it's -40F.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

May 2, 2013, 10:47 AM

Post #5 of 6 (1002 views)
Re: '97 Civic Fuel Economy Drop Troubleshooting Sign In

#3 - Forget additives. Most will cause other problems you don't need. If leaking fix it. if burning over IDK over how many miles you might just forget it. I'd check it more often and I would do 1/2 qts if it does consume some.

The super rich (seems so) fuel delivery could have washed the cylinders causing them wear OR gets into oil if bad enough and that would be so thin it both would be a poor lubricant and burn faster. Fix the rich running issue.

Maybe, maybe using proper grade of synthetic oil would reduce oil consumption - may need to use it twice to know IMO,

T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 2, 2013, 12:32 PM

Post #6 of 6 (995 views)
Re: '97 Civic Fuel Economy Drop Troubleshooting Sign In

Why would you add stop leak if you just got done saying that it wasn't leaking?

If it's burning oil, then I might agree with adding an oil treatment, not stop leak. One of those molasses thick treatments that coats everything like the old STP oil treatment. They make a lot of different supplements like that now.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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