P0420, P0300, P0302, P0303 Honda CRV 2002 - recently replaced generic catalytic converter and now having troubles starting

I purchased my car about 1.5 years ago in Costa Rica and have had troubles with it since the first time I started it. I would really love to get to the root of this and fix it once and for all, so any help is greatly appreciated!

The current issue (and ongoing issue) is that the car will randomly not start. Also, the gas mileage seems to not be good.

I purchased it with a generic catalytic converter (and thus P0420 check engine light code - told that it was due to being generic). I recently replaced it with a new, still generic, catalytic converter as my car wouldn’t start - it would turn over, but not catch. The replacement worked for about a month or two but is having issues starting again, usually if the engine is hot, at least for now. Last time this happened, the car eventually would not start at all.

In the past month, the spark plugs were cleaned and calibrated, along with a fuel injection cleaning treatment and oil change.

It’s worth noting that Costa Rica has low quality gasoline. I didn’t know that I was to purchase Super instead of Regular until recently, but even after the fuel injection cleaning treatment and staying with Super gasoline, the problem returned.

I’ve also had the fuel pump and spark plugs replaced about a year ago.

Thank you for any help!

Codes P0300, P0302, and P0303 are misfire codes.

Misfires can damage/destroy any catalytic converter.


I don’t think the generic catalytic converter would cause the engine to not start. I’m pretty sure you could start the engine and it would run reasonably well without a catalytic converter present at all. I think your engine has some other underlying issues, although I’m sorry to say that I can’t really guess what they are. I don’t think the misfires are caused by the converter, although like Tester said, misfires will damage the converter.

The age of the car, the codes listed, the fact you did not disclose the mileage makes me think the engine is worn out.

Does the engine require you to add oil between changes? How much? Has a mechanic ever run a compression test on the engine?

Check the ignition timing with a timing testing tool while somebody else cranks it. Best if it is at a time when it is having trouble starting. Take apart the air intake and pour a little gasoline directly in there to see if that makes it start. If it still doesn’t start then it’s a problem with the ignition or timing. It could be a faulty coil or igniter. If the timing is wrong then check the crankshaft position sensor and also see that the timing belt hasn’t slipped if it has one.

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First off make sure the basic stuff is in good shape. Spark plugs, engine air cleaner, fuel filter, vacuum hoses routed correctly and no vacuum leaks, engine compression good, ignition timing & advance curve correct, egr system good, pcv system good, no air intake leaks, & no exhaust leaks. If that’s all ok but the engine still balks on starting, remove the cat completely, leaving the pipe open, and see if it runs ok in that configuration (as a test). Note it will be very loud. If it runs much better, you probably have a clogged cat, which will have to be replaced. Suggest to just bite the bullet and buy an oem cat, or at least one that is Calif CARB compliant. If after changing the cat it still misbehaves, remove the muffler, as that may be clogged, doing the same sort of test. If the exhaust system is confirmed to be ok, you may still have some problems w/the ignition system and/or fuel injection system. But before speculating what those might be, the above is the first step. Note: Avoid driving the vehicle with a new cat and misfire codes present, as the misfires may damage the new cat.

My guess, since this vehicle is new to you, at some point someone has changed its configuration somehow, could just be a misplaced vacuum hose. Try to find another one to compare against.

There must be some highly qualified, experienced mechanics in Costa Rica, if you can’t find one that can deal with your misfire, bite the bullet and take it to a dealership.

It says 143,000 miles BUT I hear it’s a common practice in Costa Rica to roll back the miles so it’s hard to say for sure.

Before purchasing the car, having a compression test run on the engine was the one thing a mechanic tested and it was really good. It seems to hold oil - sorry for the vagueness of this as when it’s been checked in the past year, it’s been fine. When I first got it, I would find small oil leaks underneath

Thank you for all of this. I’ve been on a Honda forum where someone was having similar issues and realized it might be worth mentioning that I have to replace my coolant regularly. I’m not sure if that’s normal since I’m in a very hot climate or if it’s possible the coolant is leaking and causing problems.

It’s not common to have to replace the coolant. If it isn’t leaking on the outside somewhere, I might lean toward thinking you may have a head or head gasket issue. How hot is the engine getting when it will not start and about how much coolant are you having to add? Hopefully it’s just normal operating temp and not “hot” hot.

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Repeatedly adding coolant is not common. I have lived in the desert where daytime temperatures would exceed 100 degrees Fahrenheit, always ran the AC, never had to add coolant.
Agree with Scrapyard-John.
The various problems with your engine are fouling your catalytic converter, the converters are not causing the engine problems.

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Good to know about coolant. The engine temp usually runs at the normal operating temp even when it won’t start. Although, when the coolant is low, then it has gotten hot and I take care of that (replace the coolant) quickly after noticing it. Since owning the car, I’ve had to add coolant 4 or so times. I don’t see it leaking exteriorly, unfortunately.

Would replacing the head gasket fix it? Any other suggestions?

Thank you so much!

With a correctly functioning cooling system you shouldn’t need to add coolant, certainly not more than a cup every 6 months. The coolant has to be going somewhere. Possibilities are

  • external leak somewhere, but not enough to reach the ground. Coolant leaking onto the exhaust manifold will often evaporate. That sort of leak would however generally produce a slight, sweet-like odor.

  • heater core leak, if drain is clear, you’d see coolant dripping under the parked vehicle. If the drain was blocked, the coolant wouldn’t reach the ground but you might hear a sloshing sound when turning.

  • external leak that reaches the ground. place a sheet of cardboard under the car when you park it overnight, check for water spots the next am.

  • head gasket leak. coolant passages are routed very near to where coolant could leak into the cylinder w/a defect in the head gasket. If that occurred as the car sat overnight, enough coolant could wind up in the cylinders to create a cranks ok but difficult to start problem. It could also damage the cat if allowed to continue.

Figuring out what’s causing the coolant loss is probably priority one. Suggest to ask your shop to pressure test the cooling system. Not entirely definitive for a head gasket leak, but its not overly expensive test either. It might turn up the location of an external leak as well. I’d probably replace the cooling system’s pressure regulating cap also, another relatively inexpensive task.

Note that it wouldn’t be unusual to have a radiator leak on a 2002. Any 2002, not just Honda. Radiators these days just don’t last as long as radiators of yester-year.

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A pressure test like George mentioned might be a good idea. I’m not saying you’ve got head gasket issues for certain.

You can take out the pre cat converter oxygen sensor to rule out a plugged cat or exhaust, if you want. The engine will be extremely loud, so I’d only try that temporarily whenever the car wouldn’t start. I kind of doubt it’s a plugged exhaust issue, though, as that shouldn’t cause intermittent no starts.

I’m not sure…I think it might be a good idea to let a shop look at it. Let them do the pressure test, then diagnose the no start issue. Once they do the diagnosis, you could do the repairs yourself if you want to and have the ability.

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when you add coolant do you bleed the system to get the air out? if not you should.

Get the valves (lash) adjusted.


Randomly not starting could be a bad main relay or igniton switch. Not enough info is known on this issue but that would not likely cause the misfire codes.

Given the mileage which is said to be possibly higher than stated and the propensity to ignore valve lash adjustments I would take circuitsmith’s advice. That can cause misfires and if there are problems with tight lash on the exhaust valves then the engine is likely going to need cylinder head work or replacement. Hopefully that is not the case.
Easiest way to find out what is going on is by connecting a vacuum gauge.

Another problem you may have that has not come up yet is fuel injector problems. Too much fuel being passed through the injector(s) will cause flooding and also cause misfires which cause catalytic converter failures. Improper fuel pressure regulation, bad fuel injectors can contribute to this problem. Or even possibly a problem with injector signal.

The mechanic came yesterday before I was able to read your replies. Due to the language barriers, I’m not exactly sure what tests he ran but I can report on what I noticed and what we discussed.

  1. The radiator was empty

  2. He filled the radiator mostly with water (that’s what they do here) and later showed me the overflow gurgling with what appeared to be an oily light brownish color.

  3. When he started the car for a final test, I was overwhelmed by the smell of gas (no wonder I blow through it) and I saw lots of white smoke coming from the tailpipe.

  4. I asked him about the head gasket being the possible problem. He ultimately thought it was the head and head gasket, although before leaving mentioned there could be a slight chance the radiator cap could be the culprit. (That had me question a few things such as can I trust his diagnosis, but I don’t know enough to ascertain that.)

  5. He mentioned that Honda’s are expensive and not well known by mechanics in general in Costa Rica, and seemed to be suggesting I get another car that is more easily understood with cheaper and more available parts here.

Given how many problems I have had with this car and how unreliable it has been and how unskilled I am with cars, I am leaning towards his latter suggestion.

I do still want to know what if any of the new problems I have shared clearly indicate something one way or another as 1) it is helpful to learn (for myself and anyone else who may need this in the future) and 2) I’d like to be able to tell whomever I sell it to (if I go that route) what may be the issue as I would have appreciated the same when I purchased it.

Thank you!

No…I have not done this, nor have I seen a mechanic or anyone else who has added coolant to my car do this. It seems I need to learn how to do this for whatever car I have in the future. Thank you for the suggestion.