Mystery Misfire Theater
03-25-2010, 08:25 AM
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Mystery Misfire Theater
FINAL UPDATE: SOLVED! SEE LAST POST!
Hi I don't know if anyone else will care about this thread in the short term, but I am going to post my experiences here so that maybe someone else searching will benefit from it one day.
I'm having the classic "Mystery Misfire" CEL codes. Yes, I've read the FAQs, the "Under the Hood" threads going back to 2001, etc. My concern is this: there is too much voodoo and urban legend in troubleshooting this issue.
I'm going to post here my findings and how I troubleshooted the issue, no voodoo or "whacking" of engine components & sensors. Please excuse my OCD
Data (Cold hard facts)
1. CEL comes on at random times, different RPMs, and after different amounts of time from the reset of the codes.
1a. Codes: P300 (General Misfire) P301 (Cyl1 Misfire) through P304 (Cyl4 Misfire) & P1399 (General Misfire - Pending)
1b. All cylinders eventually misfire, but the codes appear separately and at different rates.
1c. P410 is a latecomer - once I replaced the PCV valve P410 showed up regularly. It refers to a very mysterious "Air Injection System"
2. The misfire either does not actually happen, or is imperceptible when driving. (The code seems to just come on)
3. Fuel economy suffering - approx. 20% fewer MPG city & highway.
3a. The exhaust has a noticeable smell of unspent gasoline.
4. It's a 2003 AP1, with ~70K miles. Two previous owners.
4a. Never less than 93 octane in the tank. Mobil 1 & now Castrol Edge 10w30 oil since owning the car.
5. The engine is making a higher-pitched but soft clicking noise (10 times/sec) [Now identified as the fuel injectors just getting older]
6. PCV valve was bad - stuck "open" - some oil on vacuum hose - replaced.
6a. Since PCV replaced: Engine sometimes "bogs" at idle when cold. More gas resolves.
Attempted Fixes (In order of attempt)
1. Ran tank to empty, filled up with Sunoco 93, added seafoam and fuel injector cleaner to tank. Check Air filter. Cleared CEL.
(Logic: Eliminate the possibility of bad gas and/or water in the gas)
Result: CEL reappears almost immediately at approximately 3500rpm in 2nd gear.
2. Replaced all spark plugs with OEM spec (NGK Laser Platinum NGK PFR7G-11S). Cleaned coil packs & connectors. Put electrical connector goo on wiring harness plugs. Torqued new plugs to exactly 18ft-lbs.
(Logic: Eliminate the possibility of bad plugs or connections to the plugs)
Result: CEL reappears about 2 days later at idle. Old plugs look great for 65K miles, gapped at about .45 to .50. All coil packs and connectors look fine.
3. Cleaned throttle body & MAP sensor hole in TB, "whacked" MAP sensor, reattached MAP sensor with zip tie. Checked voltage output of MAP sensor at idle (2.17V) to WOT (0.11V) - appears to be working fine.
(Logic: There is much urban legend about the MAP sensor, I wanted to ensure it was working properly and had the best chance to perform)
Result: MAP sensor appears fine - output is in spec with the sensor's datasheet. Throttle body almost didn't even need cleaning - looked great. CEL reappeared 100mi into a 200mi trip, at 4100rpm in 6th gear, cruising. No apparent trigger
4. Ran full OBD2 software scans. Identified hissing noise near valve cover - replaced faulty PCV valve - it was stuck "open" and had a little bit of oil on the outside connector.
(Logic: Hissing noise coming from the valve - valve would not change position.)
Result: MUCH better OBD2 mapping results seemingly in line with normal F20C specs. However, after celebrating early I made an ass out of myself when the CEL came back on on the way home. It's now throwing P410 regularly - and I am going to troubleshoot the "air injection system" next.
Ideas
Here are some next steps I plan to take with my mechanic:
1. Compression test & leakdown test (Logic: More data won't hurt - want to make sure pistons, rings, gaskets, and valves are ok)
2. Check timing chain tensioner & timing chain
3. Do a full mapping of the engine's performance via an advanced OBD2 computer/scanner - establish a baseline to compare. - DONE 3/29/2010
4. Check camshaft and crankshaft position sensors
5. Check knock sensor
6. Check wiring harness?
7. Troubleshoot P410 as in the service manual. (Air Injection System)
Feel free to post any advice; I will be posting my results as I get them. I do not plan on sacrificing chickens on the upper intake manifold, or pouring virgin blood into each odd-numbered cylinder on the next full moon.
Hi I don't know if anyone else will care about this thread in the short term, but I am going to post my experiences here so that maybe someone else searching will benefit from it one day.
I'm having the classic "Mystery Misfire" CEL codes. Yes, I've read the FAQs, the "Under the Hood" threads going back to 2001, etc. My concern is this: there is too much voodoo and urban legend in troubleshooting this issue.
I'm going to post here my findings and how I troubleshooted the issue, no voodoo or "whacking" of engine components & sensors. Please excuse my OCD
Data (Cold hard facts)
1. CEL comes on at random times, different RPMs, and after different amounts of time from the reset of the codes.
1a. Codes: P300 (General Misfire) P301 (Cyl1 Misfire) through P304 (Cyl4 Misfire) & P1399 (General Misfire - Pending)
1b. All cylinders eventually misfire, but the codes appear separately and at different rates.
1c. P410 is a latecomer - once I replaced the PCV valve P410 showed up regularly. It refers to a very mysterious "Air Injection System"
2. The misfire either does not actually happen, or is imperceptible when driving. (The code seems to just come on)
3. Fuel economy suffering - approx. 20% fewer MPG city & highway.
3a. The exhaust has a noticeable smell of unspent gasoline.
4. It's a 2003 AP1, with ~70K miles. Two previous owners.
4a. Never less than 93 octane in the tank. Mobil 1 & now Castrol Edge 10w30 oil since owning the car.
5. The engine is making a higher-pitched but soft clicking noise (10 times/sec) [Now identified as the fuel injectors just getting older]
6. PCV valve was bad - stuck "open" - some oil on vacuum hose - replaced.
6a. Since PCV replaced: Engine sometimes "bogs" at idle when cold. More gas resolves.
Attempted Fixes (In order of attempt)
1. Ran tank to empty, filled up with Sunoco 93, added seafoam and fuel injector cleaner to tank. Check Air filter. Cleared CEL.
(Logic: Eliminate the possibility of bad gas and/or water in the gas)
Result: CEL reappears almost immediately at approximately 3500rpm in 2nd gear.
2. Replaced all spark plugs with OEM spec (NGK Laser Platinum NGK PFR7G-11S). Cleaned coil packs & connectors. Put electrical connector goo on wiring harness plugs. Torqued new plugs to exactly 18ft-lbs.
(Logic: Eliminate the possibility of bad plugs or connections to the plugs)
Result: CEL reappears about 2 days later at idle. Old plugs look great for 65K miles, gapped at about .45 to .50. All coil packs and connectors look fine.
3. Cleaned throttle body & MAP sensor hole in TB, "whacked" MAP sensor, reattached MAP sensor with zip tie. Checked voltage output of MAP sensor at idle (2.17V) to WOT (0.11V) - appears to be working fine.
(Logic: There is much urban legend about the MAP sensor, I wanted to ensure it was working properly and had the best chance to perform)
Result: MAP sensor appears fine - output is in spec with the sensor's datasheet. Throttle body almost didn't even need cleaning - looked great. CEL reappeared 100mi into a 200mi trip, at 4100rpm in 6th gear, cruising. No apparent trigger
4. Ran full OBD2 software scans. Identified hissing noise near valve cover - replaced faulty PCV valve - it was stuck "open" and had a little bit of oil on the outside connector.
(Logic: Hissing noise coming from the valve - valve would not change position.)
Result: MUCH better OBD2 mapping results seemingly in line with normal F20C specs. However, after celebrating early I made an ass out of myself when the CEL came back on on the way home. It's now throwing P410 regularly - and I am going to troubleshoot the "air injection system" next.
Ideas
Here are some next steps I plan to take with my mechanic:
1. Compression test & leakdown test (Logic: More data won't hurt - want to make sure pistons, rings, gaskets, and valves are ok)
2. Check timing chain tensioner & timing chain
3. Do a full mapping of the engine's performance via an advanced OBD2 computer/scanner - establish a baseline to compare. - DONE 3/29/2010
4. Check camshaft and crankshaft position sensors
5. Check knock sensor
6. Check wiring harness?
7. Troubleshoot P410 as in the service manual. (Air Injection System)
Feel free to post any advice; I will be posting my results as I get them. I do not plan on sacrificing chickens on the upper intake manifold, or pouring virgin blood into each odd-numbered cylinder on the next full moon.
03-25-2010, 10:28 AM
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Check your wiring harness.
I had random misfires for 40,000 miles or so before anyone figured it out.
4 or 5 ECU's, new injectors, plugs, etc. later, a Honda Engineer finally came to my rescue. Once the harness was replaced, everything was good.
20% less mileage...check
strange noises from the engine...check
Random CEL's...check
Mine was a little worse in that it would seemingly be running on 2 or 3 cylinders when the major mis-fires would happen.
Frustrating...MAJOR CHECK!!
It may not be the same issue, but it's worth checking if that can be done without full replacement.
Good luck.
OH! Mine is AP1 2002
I had random misfires for 40,000 miles or so before anyone figured it out.
4 or 5 ECU's, new injectors, plugs, etc. later, a Honda Engineer finally came to my rescue. Once the harness was replaced, everything was good.
20% less mileage...check
strange noises from the engine...check
Random CEL's...check
Mine was a little worse in that it would seemingly be running on 2 or 3 cylinders when the major mis-fires would happen.
Frustrating...MAJOR CHECK!!
It may not be the same issue, but it's worth checking if that can be done without full replacement.
Good luck.
OH! Mine is AP1 2002
03-25-2010, 10:35 AM
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Penrod - first - WOW! 200k+ miles... kickass!
Second - what do you mean the "wiring harness" - surely you do not mean the car's entire electrical system... do you mean the plugs and wires sitting atop the engine under the plug cover? At what point did you sever the old wires and attach the new?
Second - what do you mean the "wiring harness" - surely you do not mean the car's entire electrical system... do you mean the plugs and wires sitting atop the engine under the plug cover? At what point did you sever the old wires and attach the new?
03-25-2010, 11:00 AM
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Luckily, I didn't have to do anything really, except endure a sucky sports car for a year and a half. Talk about patience!!
From what I saw, the wire harness that wraps the engine bay looked new when I popped the hood to inspect their handy work. I can't tell you where they severred the existing and tied in the new. I do know when I left there and got into Vtec, it was well worth the wait. It felt like the car had another 30-50 hp. I thought it was fast before, but DA-UMM!!
I don't know squat about electrical systems, so I'm not sure if there is an easy way to check something like that without checking each individual connection and each individual wire.
Hope that helps.
From what I saw, the wire harness that wraps the engine bay looked new when I popped the hood to inspect their handy work. I can't tell you where they severred the existing and tied in the new. I do know when I left there and got into Vtec, it was well worth the wait. It felt like the car had another 30-50 hp. I thought it was fast before, but DA-UMM!!
I don't know squat about electrical systems, so I'm not sure if there is an easy way to check something like that without checking each individual connection and each individual wire.
Hope that helps.
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03-25-2010, 11:03 AM
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Oh, it's only 188,000 right now, but I anxiously anticipate 200K in the next few months.
The wife drives it now, but she only puts about 30 miles per week on it getting groceries and what not.
After years of one oil change per month, the next 3,000 mile oil change comes about 5 months after the previous one.
The wife drives it now, but she only puts about 30 miles per week on it getting groceries and what not.
After years of one oil change per month, the next 3,000 mile oil change comes about 5 months after the previous one.
03-25-2010, 11:12 AM
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This is my original thread on my misfire, circa 2004:
https://www.s2ki.com/forums/index.php?showt...0&#entry4021645
Here's another one that could point to an injector issue:
https://www.s2ki.com/forums/index.php?showt...0&#entry4316249
https://www.s2ki.com/forums/index.php?showt...0&#entry4021645
Here's another one that could point to an injector issue:
https://www.s2ki.com/forums/index.php?showt...0&#entry4316249
03-25-2010, 11:35 AM
#10
Skip everything and go straight to a leakdown. Last time I had misfires I had 8 or 10 bent exhaust valves. Replaced with AP2 valvetrain and all has been well for over 15. Hell, I pegged 9600 rpm missing 2nd at around 12 psi last weekend and its still holding together.
My guess: you got some bent valves.
My guess: you got some bent valves.