I bought this car last summer (160,000 miles). Had Honda dealer change timing belt, water pump and seals last summer too. Then I changed the sparkplugs myself last summer. Everything was fine until last week, after about 4,000 miles of total driving.

1) The car had trouble unlocking like the locks were not getting enough power. So I checked the battery terminals and they were corroded. I cleaned the posts and the cable part that attaches to the battery. Everything is fine now. While under the hood, I checked the air filter, some what dirty... and made mental note to change it soon.

2) 1 week later I decided to go on the highway for about 15 miles, no problem. Coming back, the service engine light came on (not blinking), the only code was P0420 . It says several things can cause this, like A/F ( air - fuel) ratio problem, ignition problems, O2 sensor problem, or catalytic Converter problem. NOTE: I did not smell the deadly rotten egg smell.

I cleared the code just to see what happens.. fine for 3 days, but it came on again when my daughter was on the highway (never in the city).

Now i have a few questions based on looking on the internet (Yes, I work on cars but this is my first "foreign" car).

1) Is it possible that I screwed something up by disconnecting the battery and causing the memory to be lost (I don't care about the radio)? I saw something about the PCM needs to relearn the idle settings, etc.. and I have to do this by running the engine at no load at 3000 RPM for 3 minutes, then drive on the road at 45 MPH for 2 minutes, then let off the gas for 3 seconds. Is this right?
What happens if i dont drive for 2 minutes because I have to stop at a stop light?

2) While checking for vacuum leaks, I noticed the plastic air intake from the filter to the Throttle body was cracked ( 1/2 way between the filter and throttle body). I might have broke it when I checked the air filter the week before. Could this cause the air/fuel ratio problem?

3) What about the O2 sensors? It looks easy to change. Is it similar to changing sparkplugs? I haven't checked for corroded wires but will do that this weekend.

4) When I looked on the internet about CAT Converters... it was saying to stay away from Magnaflow and other certian types because they don't last long, or they don't perform well enough to prevent the P0420 code. Is this true? What about buying from RockAuto parts on the internet?
any recommendations?

5) i need to check again, but I did think I smelled gasoline fumes but at the time was not able to raise the hood. I will need to check for fuel leaks (I never saw fuel on the driveway, but it could be fumes). Can this also cause the A/F ratio problem and trigger the P0420 code?

6) looking back... i just got regular sparkplugs... is there a certain type that i should have gotten? these were normal ones, not platnium or some high dollar type.

Any other things i should look at ? I am not quite convinced that the CAT is going bad, but am looking for Vac leaks, or fuel leaks....

Thanks for any inputs!

Rob

 

have you searched on this forum for that code yet?
seems logical to do as you are most likely not the first person to have this problem

click_here_to_search_for_code_P0420

Looks like 163 existing threads about code P0420

 

Yes i checked... but i have 4 questions and was hoping someone could answer each one...

 

looks like 6 questions to me, which 4 do you want answered?

 

LOL sorry all six... but if i had to pick four... then 1-4... i am sure 5 and 6 arent a big problem

 

Ok 1-4 it is

1) Yes a dirty airfilter is bad, change it.

2) guess this isn't really a question

1b) short answer - no

2b) it will not cause A/F problems cause it meters the air at the intake so any leaks before that will get calculated. However, you should seal the crack up, wrap the intake with black electrical tape a bunch of times, it should seal up the crack just fine.

3b) yes they do unscrew like spark plugs however, you need a special socket for them and most of the time the heat / cooling cycles basically weld them in so they are real hard to unscrew.

4b) I have never heard about aftermarket converters not lasting.

5b) (this is a lot of questions, I am getting tired) a fuel leak would not likely cause an A/F ration error however, a fuel leak should be address before driving the car any further, think large fireball...

6b) NGK is the recommended plug on this forum

 

1b) Re-learning the idle - that sounds like the procedure for newer Accords...
For 1998 you can (again) reset your ECU by pulling the #13 fuse in the right-side dashboard. Near the right-front door hinges.
- Allow the engine to cool down completely.
- Start the engine without touching the gas pedal.
- Let it idle to warm up completely without touching the gas pedal.

2) Won't cause an air/fuel ratio problem. It will allow dirty air to get in past the filter, so tape it up like Crispin said.

3) The special socket allows the wire pigtail to lay in a groove alongside the wrench-hex of the sensor body. Normally you can borrow that socket from places like AutoZone.

5) Look for corroded fuel lines under the car.

6) NGK or else Denso. Stock plug should be listed in the owner's manual. Some people have reported misfiring with other brands of plugs, but other people have said they're OK...?

 

OK.. an update

1) My daughter drove around town. no problem. I drove around town, no problem. Took it on the highway... after about 10 minutes, the light came on. Cleared the light, drove around town, no problem. go back on the highway and the light came as i was going down the on-ramp (about 50 MPH). Again it was only the P0420 Cat Code. Now why only when I am going over 50 MPH will it come on and never under 50MPH. Does that say something?

2) Thanks, will try to reset the idle speed in case that might help. nothing to lose.

3) The fuel smell is coming from near the gas tank. There are several parts in that area and I believe it it more around the EVAP 2-way valve... or whatever that part is that has a cover over it. When i pop open the cover, the smell is much stronger in there. I think there is something else there too. Lets assume that part is cracked, valve stuck open, or a lose hose connection. Does that cause a vacuum leak? could this be part of the problem with the P0420 code? Or is that smell normal because it needs to vent?

4) Why does the light only come on at 50MPH and higher? could it have something to do with programming and the spark plug firing needs to be sooner? On other cars, if you change the cam shaft sensor, the ECM needs to br programmed. Does this car have one?

5) The CAT has 3 bolts on each end. and i need to remove the O2 sensor.
Will the bolts and nuts pretty much be welded/rusted together that I have to practically break/grind it off? What about the O2 sensor ? Should I run the car so those parts are hot before o try taking them off?

6) Again about ordering replacment CATS... i see on the internet that some brand I need to stay away from. Is this true? I am aware that sometimes the problem is the CAT is damaged and was caused by too much fuel... and if they replaced that cat without fixing the original problem, they shouldnt blame the brand because it had a short life.
any advice?

I do work on cars, but this is the first time i fooled with the exhaust system... It this something that is fairly straight forward? The way the CAT looks, I would rather do this, than change CV axles.

Thanks again for any advice!

 

1) I don't know

2) OK

3) fuel smell isn't normal. Keep looking for cracked parts or loose/cracked/brittle hoses.

4) no "camshaft sensor". You have sensors inside the distributor, and also down at the crankshaft front pulley. Together they control spark & fuel timing. You would throw some additional error codes if those were bad.

5) Those bolts get pretty hot, so I'd be prepared to saw them off & replace them. Maybe you'll be lucky & get them off, but if not you'll be prepared with new bolts.

6) Yeah, that's all kinda true, but hard to tell which parts really apply to you. I don't know which brands are bad 'cause I haven't had to replace mine. If something is causing a very rich mixture, you DO want to fix that before burning up a new cat.

 

Thanks to everyone who gave advice... over the next few weeks I will slowly start working on the problems.. starting with the cheapest and easiest. in this case, the order is most likely:

1) fix gas fume smell - most likely the EVAP sections and hoses.
2) tune up
3) Change Catalytic Converter and O2 sensors

One thing I wish would happen is that on this forum, it seems most people ask for advice, but rarely posts the results or solutions. If everyone would post the results of what they did, the rest of us can learn what may or may not work.

I plan to post the results, but will wait a few weeks to be sure what was "fixed" actually was fixed.