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Discussion Starter · #1 ·
Weird. Started missing but only misses until it warms up. After about a mile. Yesterday, I added 4 new spark plugs and 4 coil packs that I had for backup. Still missing. No check engine light on but I have had a light on in the last month for the catalytic converter. Any ideas what is causing the miss until it warms up? Runs fine after that. Thanks in advance.
 

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oh and its only getting 350 miles per tank which is 100 miles less than normal.
It needs to be scanned for fuel trims which should give a direction to look. Guesses can be made all day, but that's no substitute for a competent scan tool. Have the valves ever been checked or adjusted? Miles would also be helpful. Final thought would be a possible plugged catalytic converter.
 

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Discussion Starter · #4 ·
the only scan Ive had done in the past is for check engine lights. I did have a check engine light come on last week but it went off. Before it did, I had it scanned at Advance and it came back PO420 catalytic issue but it went off a couple days later. Can Advance or Oreillys scan the fuel trims?
 

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Discussion Starter · #5 ·
It needs to be scanned for fuel trims which should give a direction to look. Guesses can be made all day, but that's no substitute for a competent scan tool. Have the valves ever been checked or adjusted? Miles would also be helpful. Final thought would be a possible plugged catalytic converter.
The car has 131k but it has another engine and that engine had 32k on it when installed. Long story but the original engine burnt a valve. Ive owned it since 2016 with 65k and the valve burnt up at 112k. The only scan Ive had done in the past is for check engine lights. I did have a check engine light come on last week but it went off. Before it did, I had it scanned at Advance and it came back PO420 catalytic issue but it went off a couple days later. Can Advance or Oreillys scan the fuel trims?
 

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The car has 131k but it has another engine and that engine had 32k on it when installed. Long story but the original engine burnt a valve. Ive owned it since 2016 with 65k and the valve burnt up at 112k. The only scan Ive had done in the past is for check engine lights. I did have a check engine light come on last week but it went off. Before it did, I had it scanned at Advance and it came back PO420 catalytic issue but it went off a couple days later. Can Advance or Oreillys scan the fuel trims?
In most cases the guys at the chain auto parts stores don't have a scan tool, but have a code reader that will only read codes related to emissions. As far a scan tool the one needed must have "mode 6" to read engine and driveline info. Tha cat code isn't necessarily your problem but a symptom. If your fuel trims are out of whack it could be extra air either being allowed into the system or not enough air. Either way that could lead to the catalyst code. Check for cracks in the intake tube between the MAF sensor (located by the air filter box) and the throttle body. Without a competent scan tool everything is an educated guess. I'm betting your catalyst code was caused by too much air in the system that the MAF isn't reading and that would also make your engine run rough when cold and clear up when warm, is your idle above normal when warmed up?
 

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Discussion Starter · #7 ·
In most cases the guys at the chain auto parts stores don't have a scan tool, but have a code reader that will only read codes related to emissions. As far a scan tool the one needed must have "mode 6" to read engine and driveline info. Tha cat code isn't necessarily your problem but a symptom. If your fuel trims are out of whack it could be extra air either being allowed into the system or not enough air. Either way that could lead to the catalyst code. Check for cracks in the intake tube between the MAF sensor (located by the air filter box) and the throttle body. Without a competent scan tool everything is an educated guess. I betting your catalyst code was caused by too much air in the system that the MAF isn't reading and that would also make your engine run rough when cold and clear up when warm, is your idle above normal when warmed up?
do you think theFoxwell NT510 Elite for Honda is a good scanner?
 

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do you think theFoxwell NT510 Elite for Honda is a good scanner?
That is a great DIYer scanner, it will give you the info you seek, I also love the BlueDriver scanner that works with your phone and for around $100 it's hard to beat. That's the one I keep in my glovebox. And will work on virtually any car and comes with free updates for life.
 

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I would be suspect of the primary oxygen sensor.
I have experienced this with my '01 Accord. The heating element in the primary O2 sensor fails & when cold and the car first switches to closed loop, the air-fuel ratio is way off due to the sensor giving the wrong AFR reading to the ECU. After about 5min of driving, the car runs totally normal.
 

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Discussion Starter · #10 ·
I would be suspect of the primary oxygen sensor.
I have experienced this with my '01 Accord. The heating element in the primary O2 sensor fails & when cold and the car first switches to closed loop, the air-fuel ratio is way off due to the sensor giving the wrong AFR reading to the ECU. After about 5min of driving, the car runs totally normal.
Is that the one on the manifold at the front?
 

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thanks!. I think I’ll just go ahead and start with that one then the other one if it don’t help. Did new plugs yesterday.
In a more modern Honda (newer than 01 and possibly a 01) the ECM would throw a P0135 code indicating the engine control module (ECM) has tested the O2 sensor heater circuit and has detected a problem with the O2 sensor heater circuit in bank 1 sensor 1. That would trigger a check engine light.
 

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Discussion Starter · #14 ·
Well guys, I put a new set of plugs, 4 new coils and both 02 sensors on and it didnt fix it. It was only missing very light for maybe a mile. Today she burnt a valve. Check engine light started blinking and she lost power. Sucks 131k
 

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Burnt valve was most likely caused by the exhaust valve being too "tight" a valve adjustment would have fixed it.

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