New owner, Multiple error codes, check engine light
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New owner, Multiple error codes, check engine light
Hi all, firstly apologies if this is a duplicate issue, I could not see any thread exactly like this one. Long story short, I purchased an RX8 last week. The guy had the coils replaced 2000 miles ago and also had the compression tested at Mazda, currently the car has 74,000 miles and it is a 2005, he also gave me the paper work to prove the compression was ran. I drove it 2 hours home, no issues, no startup issues either. But then a week later it is now hitting 7000 RPMs and not going any higher. Seems a little low on idling as well. I ran a code reader and got three different error codes; P0300, P0301, P0420. The check engine light comes on when it’s hitting the 7000 RPMs but it does not always stay on. I bought the car knowing that it was going to be a pain to upkeep and I’m still ok with that, I just was not expecting it to be a week after I purchased it. I did look up the error codes and I see what they mean individually but I was curious about the lm as a whole. Any help is appreciated.
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First two are for misfire, third is for cat.
Misfire thread: https://www.rx8club.com/series-i-tec...t-here-222280/
Misfire thread: https://www.rx8club.com/series-i-tec...t-here-222280/
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Hey, not really. I looked at his paperwork again and it see that there was a fuel pump recall done, so I can rule out the fuel pump. The check engine light is on all the time and also the oil light now pops on when I push the car too hard. My debate is that I now don’t know when the coils were replaced, he said they were but I don’t see it on any paperwork. I personally think it’s the cat being clogged. Also I did notice a smell in the car, like a fuel smell, it was strong. I also realized that I have been putting in regular fuel without really thinking (but that couldn’t cause misfiring right?)
what at I am thinking is that I need to take it somewhere, because the codes are pointing to the cat, I feel confident that it is clogged or just bad but I also need the coils checked etc because now I don’t really trust the seller. The only thing I do believe is that the engine is good because I have the paperwork from Mazda to show it and also I am not really having compression issues.
what at I am thinking is that I need to take it somewhere, because the codes are pointing to the cat, I feel confident that it is clogged or just bad but I also need the coils checked etc because now I don’t really trust the seller. The only thing I do believe is that the engine is good because I have the paperwork from Mazda to show it and also I am not really having compression issues.
It sounds a lot like clogged cat, yep. Usually caused by bad coils. Try not to drive it like this, it's damaging your otherwise healthy engine.
What were the compression test results?
What were the compression test results?
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I’m not using it, I made an appointment to drop it at jensen’s tomorrorw. Morning. Do you think that I could give them the codes that point to the cat so that they don’t charge me the $100 diagnostic fee just to find out what I already know?
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and also I am not sure of the exact results of the compression, it just says that the car was taken in to Mazda because it had sat so long that it had floorded. The engine was de-flooded and a compression passed. The guy who sold it to me did mention that the cat was gutted? I think I have read about people hitting the cat for better sound and as a result it gets clogged easier?
If it's gutted, then it can't be clogged. Gutting literally means removing the catalyst, so after that it's a straight pipe. But, doing so produces the P0420 code, because now, the catalyst isn't cleaning up your exhaust. So that's part of the mystery solved, I'd say.
IF it is indeed gutted, then we're back to coils and spark plugs as the likely cause of misfire.
One other possibility is pieces of the catalyst are lodged further down the exhaust pipe or muffler and block exhaust flow. See if anything rattles around in there.
With regard to the compression test, see if the dealership where it was tested has record of the actual numbers. There's a story here every week of a dealer who doesn't know how to perform a compression test on this engine. Getting the numbers is always best.
Also flooding from sitting too long is not a thing. It flooded because a component failed.
The other thing is, if the issue consistently occurs at 7000rpm every time, then that might be a clue. A few things happen there: at 6250 the tertiary intake valves open, so if they're sticking, the engine chokes. At 7250 the VDI valve opens and can momentarily lean out the mixture, or if it's also sticky, the engine chokes.
See if you can climb past 7000 rpm at partial throttle, or if the behaviour is different between partial throttle and full throttle.
IF it is indeed gutted, then we're back to coils and spark plugs as the likely cause of misfire.
One other possibility is pieces of the catalyst are lodged further down the exhaust pipe or muffler and block exhaust flow. See if anything rattles around in there.
With regard to the compression test, see if the dealership where it was tested has record of the actual numbers. There's a story here every week of a dealer who doesn't know how to perform a compression test on this engine. Getting the numbers is always best.
Also flooding from sitting too long is not a thing. It flooded because a component failed.
The other thing is, if the issue consistently occurs at 7000rpm every time, then that might be a clue. A few things happen there: at 6250 the tertiary intake valves open, so if they're sticking, the engine chokes. At 7250 the VDI valve opens and can momentarily lean out the mixture, or if it's also sticky, the engine chokes.
See if you can climb past 7000 rpm at partial throttle, or if the behaviour is different between partial throttle and full throttle.
Last edited by Loki; Jul 16, 2018 at 10:44 AM.
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And the answer is.... the cat, some pieces had broken off inside, guy at Jensen’s mentioned the honeycomb center. Thanks everyone, I’m just debating if I should let them do the repair or do it myself.
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So just to give everyone a final update, Jensen’s replaced the cat, the coils and sparks. Picked it up today and it is driving better than ever, it is hitting the redline and sounds better, I honestly think it’s even starting up better. The guy showed me pieces of the inside of the cat that were clogging it up. Thank you all for the useful info, I’m so happy that the car is running like a champ again!
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