CEL - Random Misfire - Problem Fixed
#1
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CEL - Random Misfire - Problem Fixed
Hello UTH ,
I am trying to diagnose/fix a CEL that has been on for a few months now. After thorough searches in the UTH forum, I have tried several fixes... but the CEL comes on after a few driving cycles. The idle is sometimes rough, but overall the car runs fairly smooth. My car is stock, other than a K&N stock filter. It is a MY00 and has 87k miles.
Here's a list of fixes that I have tried:
1. New Spark Plugs
Replaced spark plugs with new NGK's stated in the TSB. After driving around 50-100 miles, the light came back on.
2. New Fuel Injectors
After reading Random1's thread about fuel injectors, I replaced all 4 of them. I noticed that the throttle response was smoother with less shaking at idle, but the CEL eventually came back on before 100 miles.
3. Cleaned the IAC valve
I found another thread about someone's s2000 getting random misfire's caused by carbon deposits in the IAC valve. Using intake cleaner, I removed the carbon deposits, reset the ECU...but the CEL came back on.
4. New PCV Valve
Since the CEL usually came on at idle, I replaced the PCV valve. I was not really convinced this was the cause of the problem, but tried it anyways. After driving less than 20 miles, the CEL came back on.
5. Compression Test
I read someone's advice about trying a compression and leak down test. Here are the results from the compression test (actron gauge from pep boys, average from 3 tests with 10 cycles each):
FROM THE FRONT OF THE CAR TO THE DRIVERS SEAT
Cylinder 1 = 220
Cylinder 2 = 250
Cylinder 3 = 235
Cylinder 4 = 235
I read that a variation from max to min should be no more than 10%, or if the PSI is above 200, it is fine? My max to min variation is a little above 10%, so I am not sure if I should worry about cylinder 1(or what to do?). I plan on adding a teaspoon of oil to cylinder 1 and trying the compression test again, to make sure it there is no seal leak.
Based on the compression test, should I be worried about bent/burnt valves?
6. Several MAP whacks with tiedowns
On another thread, I read that the connectors to the MAP sensor can come loose due to the vibrations in the engine. So I tried the MAP whack, and added tiedowns to secure it. After relearning the ECU, the CEL would come back on.
I am currently in the process of borrowing a friends air compressor and leak down tester, so I will try a leak down test this weekend. Other than that, I am out of ideas on what to try next.
Please help! I am stumped
I am trying to diagnose/fix a CEL that has been on for a few months now. After thorough searches in the UTH forum, I have tried several fixes... but the CEL comes on after a few driving cycles. The idle is sometimes rough, but overall the car runs fairly smooth. My car is stock, other than a K&N stock filter. It is a MY00 and has 87k miles.
Here's a list of fixes that I have tried:
1. New Spark Plugs
Replaced spark plugs with new NGK's stated in the TSB. After driving around 50-100 miles, the light came back on.
2. New Fuel Injectors
After reading Random1's thread about fuel injectors, I replaced all 4 of them. I noticed that the throttle response was smoother with less shaking at idle, but the CEL eventually came back on before 100 miles.
3. Cleaned the IAC valve
I found another thread about someone's s2000 getting random misfire's caused by carbon deposits in the IAC valve. Using intake cleaner, I removed the carbon deposits, reset the ECU...but the CEL came back on.
4. New PCV Valve
Since the CEL usually came on at idle, I replaced the PCV valve. I was not really convinced this was the cause of the problem, but tried it anyways. After driving less than 20 miles, the CEL came back on.
5. Compression Test
I read someone's advice about trying a compression and leak down test. Here are the results from the compression test (actron gauge from pep boys, average from 3 tests with 10 cycles each):
FROM THE FRONT OF THE CAR TO THE DRIVERS SEAT
Cylinder 1 = 220
Cylinder 2 = 250
Cylinder 3 = 235
Cylinder 4 = 235
I read that a variation from max to min should be no more than 10%, or if the PSI is above 200, it is fine? My max to min variation is a little above 10%, so I am not sure if I should worry about cylinder 1(or what to do?). I plan on adding a teaspoon of oil to cylinder 1 and trying the compression test again, to make sure it there is no seal leak.
Based on the compression test, should I be worried about bent/burnt valves?
6. Several MAP whacks with tiedowns
On another thread, I read that the connectors to the MAP sensor can come loose due to the vibrations in the engine. So I tried the MAP whack, and added tiedowns to secure it. After relearning the ECU, the CEL would come back on.
I am currently in the process of borrowing a friends air compressor and leak down tester, so I will try a leak down test this weekend. Other than that, I am out of ideas on what to try next.
Please help! I am stumped
#4
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Hi Ckit / Enthralled,
I was hoping the tiedown will "fix" any issues with the MAP sensor, but I will buy a brand new one and see if that works.
For the spark plugs being loose, I used a torque wrench everytime I reinstalled the spark plugs to 18 ft/ pounds. The spark plugs were never loose when I tried to uninstall them, so I do not think they were loose.
I tried to move around the coil packs, but I still get the random misfires. I am thinking all 4 coil packs would not go bad at once, so I ruled that out. Do you know of a way to test individual coil packs?
Enthralled, the car has never had a valve adjustment. Could a valve adjustment fix random misfire problems?
I am not sure when the car needs a valve adjustment, but I will try that soon.
Thanks for your help! I will try these fixes, and see if they work. If you can think of anything else, please let me know.
I was hoping the tiedown will "fix" any issues with the MAP sensor, but I will buy a brand new one and see if that works.
For the spark plugs being loose, I used a torque wrench everytime I reinstalled the spark plugs to 18 ft/ pounds. The spark plugs were never loose when I tried to uninstall them, so I do not think they were loose.
I tried to move around the coil packs, but I still get the random misfires. I am thinking all 4 coil packs would not go bad at once, so I ruled that out. Do you know of a way to test individual coil packs?
Enthralled, the car has never had a valve adjustment. Could a valve adjustment fix random misfire problems?
I am not sure when the car needs a valve adjustment, but I will try that soon.
Thanks for your help! I will try these fixes, and see if they work. If you can think of anything else, please let me know.
#5
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Location: Fair Oaks, CA
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what codes are you getting?
I had P0301,P0304,P0300. One time they went away.
My cel came back with stall at idle, clutch in.
I cleared codes and they did not come back, and the stall was still there.
I ( I noted when I pulled plugs 1 and 4 did not look normal color. )
I went fm cel to stall at lite, clutch in.
Took to dealer and diagnosis said poor compression in cyl 1 and 4.
Bad exhaust valves, cyl 1 and 4. They are changing the head.
I hope to get back Sat.
Hopefully you do not have same problem.
PM if you want follow up.
I had P0301,P0304,P0300. One time they went away.
My cel came back with stall at idle, clutch in.
I cleared codes and they did not come back, and the stall was still there.
I ( I noted when I pulled plugs 1 and 4 did not look normal color. )
I went fm cel to stall at lite, clutch in.
Took to dealer and diagnosis said poor compression in cyl 1 and 4.
Bad exhaust valves, cyl 1 and 4. They are changing the head.
I hope to get back Sat.
Hopefully you do not have same problem.
PM if you want follow up.
#6
Join Date: Mar 2007
Location: Point Loma & Modesto, CA
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man....we all been having the same problem... i'll be taking my car to the dealer monday and see what they say.
i get back to you guys about it.
what about you guys. heard anything yet?
i get back to you guys about it.
what about you guys. heard anything yet?
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#9
Replace the MAP yet? Also maybe an O2 sensor going bad?
We need the CEL #'s to have a better idea. Also do the valve adjustment, it's not hard and requires only to buy some feeler gauges. I am pretty sure there is an excellent walk through in the stickies.
We need the CEL #'s to have a better idea. Also do the valve adjustment, it's not hard and requires only to buy some feeler gauges. I am pretty sure there is an excellent walk through in the stickies.