p0300 w/ intermittent flashing ses

[04xuv]

was heading out when the truck stalled at a red light. restarted and the ses started flashing. about a mile from the house so i limped back and checked the code: p0300. TB was cleaned last summer, so i guess i'll go ahead and do it again. i'll also check the coils and plugs while i'm at it. plugs are iridiums, changed last year as well. could it be the o2 sensor? anything else it could be? truck has been running great until this happened. over the past year and a half that i've had it, it's shut off at red lights 3 or 4 times. never consistently. only other reason i can think this happened is that i paid it off earlier this week.

also, i cleared the code, and it came back the same. no p030x.
i'd appreciate any help.

 

[The_Roadie]

Flashing SES means don't drive it, because unburned fuel is going to burn inside, and potentially damage, your cat. Could be plugs or coils, water/oil in a plug well, CPAS. A good scan tool can look at the O2 sensor data and see if it's bad, but typically those faults would have additional error codes and not just the misfire. Also check the timing advance with the scan tool. Some faults do not respond well or quickly to guessing. Troubleshooting it properly needs more electronic tools.

Also check for vacuum leaks and loose intake manifold bolts.

 

[04xuv]

Flashing SES means don't drive it, because unburned fuel is going to burn inside, and potentially damage, your cat. Could be plugs or coils, water/oil in a plug well, CPAS. A good scan tool can look at the O2 sensor data and see if it's bad, but typically those faults would have additional error codes and not just the misfire. Also check the timing advance with the scan tool. Some faults do not respond well or quickly to guessing. Troubleshooting it properly needs more electronic tools.

Also check for vacuum leaks and loose intake manifold bolts.

haven't checked all the plugs,yet. but pulled number 3 and 4 coils and looked around. no oil or water. will check the rest shortly, once the engine cools down some. obdwiz does not check o2 sensor data. may have to splurge for better software. timing advance read as 11.5 with a minimum 4.5 and a maximum 26.5. don't know what this means, as it didn't give me what unit it was measured in (not that that would help me).

don't know how to check for vacuum leaks. manifold bolts are secure.

any chance this is just bad gas. got it from my normal station, but anything's possible.

 

[04xuv]

if i remember correctly, the ses only flashed when i was trying to accelerate. it would go off when braking or coasting.

 

[04xuv]

Just plugged the scanner back in. It read p0304. So I switched the number 4 pack with the number 3. Read it again. Now it says p0300 again. Any ideas?

 

[Matt]

Just plugged the scanner back in. It read p0304. So I switched the number 4 pack with the number 3. Read it again. Now it says p0300 again. Any ideas?

Yes. Replace that coil. It should eventually read P0303. What you did was move the bad coil to a different position, so it now sees a good coil in #4 and a bad coil "somewhere". It will probably take a couple of drive cycles for #3 to show bad.

 

[Mooseman]

#4 coil has a high failure rate due to water dripping from the cowl that is directly above it, which seems to be what happened here.

 

[CaptainXL]

could it be the o2 sensor? .

Always a good idea to change the upstream O2 when changing over to Iridium plugs at 100, 000 miles.

Also check the camshaft position sensor to see if the holdown bolt is loose.

Also run a few bottles of Chevron Techron Concentrate Plus over the next couple fillups.

Wouldnt be a bad idea to check the compression in each cylinder to see if you have a valve problem.

Any one of these things (including plugs or coils) can cause a a P0300.

Also, its probably a good idea to replace the ignition switch and have the battery and alternator tested. Low voltage can cause a number of problems which can alter the way the PCM delivers fuel.

 

[04xuv]

Yes. Replace that coil. It should eventually read P0303. What you did was move the bad coil to a different position, so it now sees a good coil in #4 and a bad coil "somewhere". It will probably take a couple of drive cycles for #3 to show bad.

yup. p0303 showed up about 10 last night. so I went to aap this morning, got a new coil and installed. only an hour late for work.
I put the new one in the #3 position, since that's the one I switched with bad #4. i was thinking of moving the new one to the #4 position. does it really matter, though?

thanks everybody for replying.

 

[04xuv]

Always a good idea to change the upstream O2 when changing over to Iridium plugs at 100, 000 miles.
wasn't the problem this time, but maybe i should do it anyway. don't know the maintenance history.
Also check the camshaft position sensor to see if the holdown bolt is loose.

Also run a few bottles of Chevron Techron Concentrate Plus over the next couple fillups.
better than seafoam? different? i did seafoam on the last tank. will probably do again on the next. what about a higher octane?
Wouldnt be a bad idea to check the compression in each cylinder to see if you have a valve problem.

Any one of these things (including plugs or coils) can cause a a P0300.

Also, its probably a good idea to replace the ignition switch and have the battery and alternator tested. Low voltage can cause a number of problems which can alter the way the PCM delivers fuel.
i can see testing the battery and alternator. but why replace the ignition switch?

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[Matt]

yup. p0303 showed up about 10 last night. so I went to aap this morning, got a new coil and installed. only an hour late for work.
I put the new one in the #3 position, since that's the one I switched with bad #4. i was thinking of moving the new one to the #4 position. does it really matter, though?

thanks everybody for replying.

It won't matter. But you may want to look at doing the mod to the rubber stripping to decrease the likelyhood of more water dripping on to #4.

 

[CaptainXL]

wasn't the problem this time, but maybe i should do it anyway. don't know the maintenance history.

It needs to be done at 100,000 miles according to the maintenance schedule in the owners manual.

Not knowing the maintenance history and playing ignorant hoping things resolve themselve is just asking for trouble. Better to take a couple plugs out and check to see if they have already been changed over to Iridium. If they have then you shouldn't need to worry about it.

Is Chevron Techron better than seafoam? different?

Yes, it's much better. Techron has scientifically proven cleaners that remove fuel injector and combustion chamber deposits.

i did seafoam on the last tank. will probably do again on the next. what about a higher octane?

Seafoam is 1940's marine engine technology. The chemicals in it don't do any more in modern fuel systems than dry up the fuel system. In which case you can use ISO-Heat for that. But this is summer so I digress. I don't use seafoam. I would rather spend my money on more effective products.

i can see testing the battery and alternator. but why replace the ignition switch?

The ignition switch is a known weak point in the ignition system and is recommended to replace it if you feel it will help simplify troubleshooting ignition related or engine related issues. Most people don't have the time nor patience in testing the ignition switch. Besides it can be flaky and testing it multiple times might yield different results. In which case most just replace it and move on to troubleshoot other/easier things.