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I drive Civic AT and it is very bad on milage. It gives 5.5km/L. I checked the ignition system by removing the ignition connectors of each cylinder. Found problem with 3rd cylinder ignition system. When I unplug the 3rd connector ,engine is idealing sometimes in the perfect RPM and sometimes not. I start the engine and i feel all cylinders are firing. When I unplug the third connector the engine runs rough and slow trying to reach ideal rpm. But when I plug it back I find no change or increase in RPM. So before unplugging it runs smooth and when I unplug and plug it back it runs d same way as low rpm and rough. Can some one help.
When you removed the third ignition during the Power Balance (rpm drop) test you just performed did you listen for spark quality while slighlty lifting the ignition coil off the spark plug? Also, try swapping the third cylinder ignition coil with another cylinder (ex: 4th cylinder) and see if the same problem occurs in the swapped cylinder
If it's getting good spark then it could be either a compression: intake/ehaust valves leak or cylinder compression rings leak OR the valves may need adjusting (if they are adjustable?). Hopefully, it's either a bad coil or spark plug.
I drive Civic AT and it is very bad on milage. It gives 5.5km/L. I checked the ignition system by removing the ignition connectors of each cylinder. Found problem with 3rd cylinder ignition system. When I unplug the 3rd connector ,engine is idealing sometimes in the perfect RPM and sometimes not. I start the engine and i feel all cylinders are firing. When I unplug the third connector the engine runs rough and slow trying to reach ideal rpm. But when I plug it back I find no change or increase in RPM. So before unplugging it runs smooth and when I unplug and plug it back it runs d same way as low rpm and rough. Can some one help.
What year and model is this car? What engine size?
What fault codes did it have before you started disconnecting ignition parts? (always check fault codes first, because as you messed with it it's likely you caused more new codes) You might need to erase all fault codes and start fresh, drive it until it sets faults again and read/report the codes
A failure strategy in some engine control units is once a severe misfire has been detected, the computer has the ability to disable the fuel injector for that cylinder (or bank of cylinders on a "v" engine)--- so even though you reconnected the coil, the computer does not allow that cylinder to operate again, until some certain criteria are met.
When you removed the third ignition during the Power Balance (rpm drop) test you just performed did you listen for spark quality while slighlty lifting the ignition coil off the spark plug? Also, try swapping the third cylinder ignition coil with another cylinder (ex: 4th cylinder) and see if the same problem occurs in the swapped cylinder
If it's getting good spark then it could be either a compression: intake/ehaust valves leak or cylinder compression rings leak OR the valves may need adjusting (if they are adjustable?). Hopefully, it's either a bad coil or spark plug.
Hey, Thanks for ur message. Checked the misfires and everything is fine now. Somehow i don't find the same problem existing. Sark plugs and coils are also fine and i have checked the coils on a multimeter. I suppose i have a problem with my oxygen sensor as the harness connectors are showing only 8,5 volts. one shows 8.5 Volts and the other shows 7.5volts. Pre catalytic O2 sensor shows 3.4ohms between the heater terminals and the other shows 7.5 ohms between heater terminals(black). Also bank 1 Sensor 1 of O2 doesnt showup any data.
Again: What year is your car and what engine size?
If your car has an AF sensor in the primary location, many scanners don't display data that is actually usable to you because its operating characteristics are very different from an oxygen sensor.
You disconnect sensor therefore you caused codes? Reconnect all sensors and erase all codes.
Your car at this time has NO CODES while operating and driving normally?
Hi
My vehicle is CIVIC 2007 SAT. It's a Preowned vehicle which I purchased 3 months back, so a bit of anxiety on the components as its preowned The issue I am trying to solve is low fuel economy(6.5 KM per liter without AC).
Yes, the fault codes have shown up when I unplugged the O2 connectors and I have cleared them and is running normally.
I have used LAUNCH professional scanning tool and it has shown me that oxygen sensor bank 1 sensor 1 is just "on" and no voltage is displayed. If I get a chance I will get to the mechanic back and search for AF sensor option.
The below are few diagnostics of the vehicle which I did which may help you to analyze.
1. The exhaust smells like an LPG. I feel a lot of unburnt fuel coming out of the exhaust.
2. As soon as I start the engine within 90 seconds it goes into closed loop fuel system using O2 sensor for fuel mix which I noticed in torque mobile app. But the RPM doesn't drop to idle rpm very soon. In the cold start the rpm will be at 1300 and slowly drops to idle rpm to 758 in about 4-5 minutes.
3. Sometimes during the automatic gear shift the vehicle punches.
4. I have started the engine and then removed the connectors of pre and postcat sensors and checked the voltage across the heater terminals. The precat is not showing zero voltage and post cat shows 12V. Here again, I see a problem with precat compared to postcat.
5. The resistance value across the heater terminals of sensors of precat is 2.5 ohms and post cat is 3.9ohms.
The below are the values I noticed from the Android OBD apps.
1. I have noticed no android OBD apps shows O2 sensor bank 1 sensor 1 on my vehicle. AND I dont see anything as Air Fuel sensor.
2. O2S1 Eq is always 0.98 to 1.
3. O2 sensor bank 1 sensor 2 value fluctuates between 0.1 to 0.7.
4. Short term fuel trim is always and greater than -18%. upon 2500 rpm it is 12%. upon cold start, it is -20%. when the engine has warmed up and moving at normal speeds its fluctuates between -12 to 18%.
5. Vacuum is 18 Hg at 800 rpm and 20Hg at 3000 rpm.
6. Mass air flow sensor value is 2.84g/sec at 800 rpm and 7.58g/sec at 3000 rpm.
7. Air fuel command and Air fuel measured is almost near to each other and in sync at different rpms nd the value is in and around 14.6 to 14.8
All the values are noted when the engine is hot that is after 10 mins of start.
The below are the screen shots at 750 rpm. THE BELOW ARE THE SCREEN SHOTS AT 2500RPM.
I can only list a few suspects that I would want to investigate further
Valve adjustment
MAF sensor (Skewed sensor? Contaminated? Air flow disrupted? Non-stock filter housing? Not an aftermarket air filter?)
Primary sensor (A/F) problem
Hey,
Thanks for your message.
{Recalling this thread- Low fuel economy, gaseous smell from the exhaust and fuel trims greater than -15%}
Tested the components as suggested by you.
I have back probed the Upstream Air fuel sensor and found that the voltages are 0.2V as the manimum and 0.6 as the maximum. I have taken out the sensor and heated with a butane torch and found the voltages to be as same . The voltage is not reaching to the maximum which is 0.9V, however, it falls quickly to 0.1 or less upon removing the fire.
So based on the voltages I believe its a problem with the AF sensor. Would this be a major cause for low fuel economy?.
I have tested the MAF sensor with a multimeter and found its working fine.
On a bottom to top approach, To confirm if its a problem with Airfuel sensor, can I Interchange the downstream and upstream sensors(i will do a manual wiring by back probing since the connectors don't match.) The downstream sensor works fine as it shows values from 0.2 to 0.75V. ( I meant I will remove the downstream sensor and place it in the upstream hole and connect the wires manually and so as for the post cat). So now if the fuel trim drops from 18% to anywhere near to 0 %, I will confirm its a bad AF sensor which my car has earlier.
Hi,
Thanks for your reply.
So I got to buy a new AF sensor. Am from India and I have difficulty buying a new AF sensor as the Honda Service Stations doesn't sell to outside people. I Couldn't even find a new one in any online store serving India. I have found an universal AF sensor from the following link. https://www.banggood.com/Universal-4...l?rmmds=search (This has four wire and it fits into the socket of my vehicle) .
SO CAN I PURCHASE THIS...?
The following is the way I have tested my AF sensor. I think this is the way of testing a few AF sensors.
Somehow the ground and signal wire couldn't respond to a multimeter voltage setting. So I have connected the two multimeters in series as shown in the following way as shown in the picture.
If you walk up to your local Honda dealers parts department counter with money, they won't sell you parts for your car?
I and most other regular posters here strongly urge you to only install the same brand the factory originally installed in the car.
Your factory installed AF sensor has a brand name stamped on it, it was either DENSO or NTK. (probably denso if I remember correctly)
Find what brand your original sensor is and go to that manufacturers website and look up what part number yours should get.
Then google search that part number and see what's available for you to purchase. Try to purchase from reputable suppliers.
Beware of counterfeit products that bear the name you desire (counterfeit parts are a huge problem and it's worldwide). Beware of false claims and imitations, there are MANY other brands and suppliers that don't make it obvious what they are trying to sell you is some other brand than what you want.
There is a LOT of JUNK sold over the internet and in discount parts stores.
Hondas sometimes don't like low quality parts. You can pull all of your hair out trying to figure out a problem caused by a brand new part that doesn't play well with the car.
08-05-2018
