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DQ2000CIVIC · Nov 30, 2011, 06:57 AM

I cannot figure out why it is running rich and getting poor gas mileage. I know that cylinder 3 is low on compression. We think this is due to a bad fuel injector caused that cylinder to run lean and burnt up some valves. But why would it run rich? I just replaced all fuel injectors and I am still getting bad gas mileage. Around 25-27 if I drive pretty easy. And there is no CEL on. What do I look into next without spending tons of cash? I plan on changing out the valves sometime soon but I fear that is not the only problem.

TxGreaseMonkey · Nov 30, 2011, 08:05 AM

A faulty Engine Coolant Temperature (ECT) Sensor often causes poor gas mileage, by causing the engine to run rich. Easy to replace.

DQ2000CIVIC · Nov 30, 2011, 08:17 AM

Hey Greasemonkey,

I replaced that and the thermostat along with some pieces in the distributor like you told me last time. DO you think my ECU could be faulty? And the PCV valve may have fixed my engine dying after a few miles but I am at a loss. What would cause the STFT to be off?

TxGreaseMonkey · Nov 30, 2011, 08:27 AM

Completely go over the ignition system. Since you replaced the ICM and coil, ensure the distributor cap, rotor, and spark plug wires are in great shape. Also, be sure to only use NGK spark plugs in your Honda.

Your ECM is likely fine.

DQ2000CIVIC · Nov 30, 2011, 08:33 AM

I replaced cap and rotor and I think we did the coil and ICM. I need to check that out and basically all I have left if the plug wires. What if these are all good? Any other problem solving ideas?

TxGreaseMonkey · Nov 30, 2011, 08:33 AM

. Check for codes.

. A bad oxygen sensor can radically affect gas mileage, since it controls fuel injector duration.

. Check the timing with a timing light.

DQ2000CIVIC · Nov 30, 2011, 08:43 AM

NO CEL showing!!

I am pretty sure the upper O2 is fine as I just replaced it but the lower I put a spark plug defouler on to pull it a little further away from the CAT. Since I am sure the CAT is probably shot with all these other problems. Would this be the problem? I hope not because a new CAT and O2 sensor would be more money than I have. I am running out of options it seems and I really do not want to take it to any other mechanics as they have ripped me a new one with this car. And I'd like to not need Honda to diagnose it either... they'd tell me to replace everything including the seats.

TxGreaseMonkey · Nov 30, 2011, 08:46 AM

A failing catalytic converter would certainly affect gas mileage. How many miles, however, are on the car?

DQ2000CIVIC · Nov 30, 2011, 08:49 AM

It has about 154000 on it total but I could easily spend another 1000 with all the things it needs. What should I tackle first to help alleviate tons of cost??

TxGreaseMonkey · Nov 30, 2011, 08:56 AM

From afar, it's pretty hard to say, since the engine is running fine, there are no codes, and many items have been replaced already.

DQ2000CIVIC · Nov 30, 2011, 09:00 AM

Thanks for the help but I guess I am stuck. I don't know what to do. I guess the CAT could be clogged and I could gut it to see what happens since it is junk anyway.

TxGreaseMonkey · Nov 30, 2011, 09:09 AM

Maybe the thing to do is just drive it the way it is, until a code is thrown or it becomes apparent where the problem is. Remember, gas mileage drops in the winter anyhow.

DQ2000CIVIC · Dec 1, 2011, 06:18 AM

Is it accurate to check the resistance of your spark plugs wires to tell if they are bad?

Stratmando · Dec 1, 2011, 06:20 AM

How's your Air Cleaner?
Any Brakes dragging?

DQ2000CIVIC · Dec 1, 2011, 06:40 AM

Filter looked pretty good but I am trading it out anyway today. Brakes should be fine... I never use them... JK. The gas mileage was down about 10% in the summer and fall. Now it seems it will be 15 - 20% below normal. I do not have access to a OBDII scanner at all times to keep an eye on the STFT which had told me I was running at -17... which is very rich from what I know. But I am no expert

TxGreaseMonkey · Dec 1, 2011, 07:05 AM

Ohms testing spark plug wires is fine.

Stratmando · Dec 1, 2011, 07:11 AM

DQ2000, yea, brakes are for sissys?
You could jack up the car and see if they all spin freely, can't hurt.
Good Luck

DQ2000CIVIC · Dec 1, 2011, 07:14 AM

Do you know a basic reading that they should be at? I currently have the NGK plug wires on the car. I am a newbie to the voltmeter. If I put it on the 2000k setting from the dial and I get a 6... is that 12000K or is it the other way around? But the readings were:

#1 - 6 on 2000k
#2 - 6 on 2000k
#3 - 5 on 2000k
#4 - 4 on 2000k

TxGreaseMonkey · Dec 1, 2011, 07:28 AM

Check the booklet that came with the multimeter, to be sure. I would say your readings are 4,000 ohms to 6,000 ohms, which are very good numbers.

DQ2000CIVIC · Dec 1, 2011, 07:42 AM

That would have been wise. I thought they'd be able to use a multiplier. The meter instructions say it reads up to 2000k... so I assume those readings are garbage.. right??