Rep Power: 0

Hi!!

I am new to the forum (I have been a viewer for awhile....)

My 2005 Civic EX (Auto) has had some strange problems lately. It all started one night on the drive home from work. It turned over hard, then stalled while driving, barely started again, then was fine. I took it to Auto Zone and pulled the codes. Only code was the Cam Position Sensor. I replaced it, no more code.

Then shortly after I added some Lucas Fuel Treatment (not blaming this, just noting it), and I started getting O2 P0420 codes. Then one morning is was about 10 degrees and the car would not start, it would just crank and sputter occasionally. I cleaned the plugs (which were wet), but that did not help. Eventually I figured out that if I moved the key from off to on (not running) to prime the fuel pump a few times it would start.

Once the car is running it is fine. It also starts no-problem throughout the day, mornings seem to be a problem.

I also just got several codes (they repeat after I clear them) for the TPS. I went ahead and replaced that, which seems to have taken care of my intermittent shifting issue that came up in the last couple of weeks (the transmission would not kick-down and would only up or down shift at high RPMs, if I restarted the car it would be fine).

So, the only major outstanding issue is the hard start in the morning. Could this be a fuel pump?

I am guessing the P0420 code means that I need a new cat.

Any input is greatly appreciated. It is so strange that all of these problems have came up recently; I am trying to triangulate them to one single item causing everything, but I cannot figure that out yet. The car only has 78,000 and has been decent (except for the head gasket problem).

Thank you,

Bob

 
Rep Power: 211

With 5th thru 7th gen Honda's it's best to turn the key to second position until the orange CEL light or red SMS light (I forget which one) blinks 3 times. This allows enough time for the pump to prime before turning the key to position three (start).

P0420 might be related to o2 (A/F) sensor. Denso/NTK/NGK are open and can be found for around $60-$70 online. If that's the issue!

 
Rep Power: 0

I tried letting the fuel pump prime several times, no success. Now that it is -3 F outside it will not start at all.

 
Rep Power: 211

Has it been losing coolant. You mentioned the plugs were wet: gas, oil or coolant? I ask because coolant leaking into one or more cylinders via a headgasket breach, cylinder head crack or crack in the block can cause the very issue you initially described: hard starts in morning when engine is cold. After the engine gets to operating temp then the issue (mostly) seals itself, engine runs smooth and starts properly. Hopefully, that's not the case.

7th gens (unlike 5th and 6th gens) uses an A/F (air/fuel) sensor and not an o2 sensor. Though they look very similar to each other they are not the same:
​​​​https://www.tirereview.com/air-fuel-...xygen-sensors/ You may want consider purchasing a new one..use oem only: ntk/ngk/denso (search for lowest price of the 3 brands).

 
Rep Power: 0

It does use some coolant. The level dropped from mid to low over 12 months. The dealer did the head gasket when I bought it 12k ago, they said the head looked fine. The car had the symptom where when you let it return to idle the heat would stop.

I took it to a local mechanic today and they could not figure it out. Then I brought it to my local Honda dealer, same thing. They are going to wait until tomorrow AM when it is cold to try and catch the problem.

 
Rep Power: 0

Update: Dealer thought the A/F sensor was bad and needed spark plugs. I replaced all of these and it did start this morning (7 degrees F). However, time will tell if that took care of the problem. My theory is that the A/F sensor was causing it to flood the engine, which is why the spark plugs were drenched in fuel. I still have a P0420 code, which is likely due to the catalytic converter being flooded with raw fuel. I will probably replace this next.

 
Rep Power: 211

Your theory is correct and why I mentioned " you stated your plugs were wet" You did not state prior what caused the wetness so it sounds like it was fuel causing it.

Try resetting the ECU to hopefully stop the CEL. Here's a the procedure:
1) Disconnect negative terminal (only) from battery
2) Turn on you headlights to bright and step on brake pedal to drain residual voltage from electrical system
3) Turn off headlights and all electronics ( stereo, climate control, das lights, dome light, etc..)
4) Reconnect negative terminal to battery
5) Start car and let it idle ( keep all electronics off) until radiotor fan engages (roughly 15-20 minutes).