Last week I noticed a misfire at idle. When the hood was up at idle engine would shake intermittently and I could hear it in the exhaust. Then when at idle in drive I could feel the whole vehicle shake randomly. When I released pressure on the brake just enough to move forward it would lurch forward right after it missed. Could not feel it miss while driving and no CEL ever. I can say MPG was down. 12-13 in town, but it has never been great. Plugs were replaced June of 2018 with OEM Denso SK20HR11s at approximately 125K miles. I have a Flowmaster muffler and K&N drop in air filter on it but everything else is Factory. Always run 87 octane. I have used Lucas Upper Cylinder lubricant and fuel injector cleaner occasionally. Always run synthetic oil. Granted it is lifted on 35s and everything works a little harder. My wife and I have no issue using the skinny pedal when needed! Pull a trailer very rarely. We do load it up with 4 people, 2 Giant dogs, and luggage and make 300 mile trips to NC and back on I-95 at typical I-95 left lane speeds......
Now with 157K miles total and 32K on the plugs they were worn to the point the gaps were all over .070 inches or 1.75mm. See Pic with gapper for representation of all plugs. Factory gap is .043 per the owners manual. The pencil lead thin center electrode was more or less gone on all 8 plugs, See Pics. There was a little oil on 4 (Not all from one bank) of them which, more so on one, which is likely a very small leak from the spark plug tube gaskets but not enough to warrant pulling the valve cover to replace the gaskets, IMHO. A few of them had some Corona Staining. More info on that here - Corona Stain. I wonder if I got a bad batch of Denso Plugs?
I am fairly sure the factory plugs were Denso and did not look like this when they were removed at 125K Miles.. I installed NGK Laser Iridium ILFR6T11 / 4904s this time since the Denso plugs wore so quickly. I very delicately checked the .043-.044 gap of each new plug, did not need to adjust any of them. I know in theory Iridium plugs come pregapped but I always check. Torqued to 15 ft lbs or 180 inch lbs which ever torque wrench you happen to have.
I spent an hour cleaning all the carbon out of the throttle body with CRC Throttle body & Air intake cleaner with shop rags and Q-tips. I have never cleaned it before so some of it was very stuck on. I did not fully remove the throttle body from the vehicle, but I pulled the 4 screws and freed it from the rest of the intake and had the air cleaner housing and tube out anyway due to the spark plug change. Looked shiny and new when I was done.
Also used CRC Mass Airflow Sensor Cleaner on the MAF.
Added about 30 oz of techron Complete fuel system cleaner to the already full tank, sadly it is only 87 in the tank currently. Will run it down to the gas light, refill with premium, run it to the gas light. Refill again with Premium and another 30 oz of Techron fuel system cleaner.
Had the Negative battery cable pulled for the entire time. So of course is sputtered the first start attempt and then fired right up. Between yesterday afternoon and this morning we have driven over 120 miles of mostly town traffic and the MPG indicator is at 14.4. I usually only see that high on the highway on extended trips. No CEL, No detectable Misfires. Hope to see the MPG continue on the current course. Definitely a +/-10%ish improvement. Will see on next 300 mile NC drive for Highway MPG.
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Now with 157K miles total and 32K on the plugs they were worn to the point the gaps were all over .070 inches or 1.75mm. See Pic with gapper for representation of all plugs. Factory gap is .043 per the owners manual. The pencil lead thin center electrode was more or less gone on all 8 plugs, See Pics. There was a little oil on 4 (Not all from one bank) of them which, more so on one, which is likely a very small leak from the spark plug tube gaskets but not enough to warrant pulling the valve cover to replace the gaskets, IMHO. A few of them had some Corona Staining. More info on that here - Corona Stain. I wonder if I got a bad batch of Denso Plugs?
I am fairly sure the factory plugs were Denso and did not look like this when they were removed at 125K Miles.. I installed NGK Laser Iridium ILFR6T11 / 4904s this time since the Denso plugs wore so quickly. I very delicately checked the .043-.044 gap of each new plug, did not need to adjust any of them. I know in theory Iridium plugs come pregapped but I always check. Torqued to 15 ft lbs or 180 inch lbs which ever torque wrench you happen to have.
I spent an hour cleaning all the carbon out of the throttle body with CRC Throttle body & Air intake cleaner with shop rags and Q-tips. I have never cleaned it before so some of it was very stuck on. I did not fully remove the throttle body from the vehicle, but I pulled the 4 screws and freed it from the rest of the intake and had the air cleaner housing and tube out anyway due to the spark plug change. Looked shiny and new when I was done.
Also used CRC Mass Airflow Sensor Cleaner on the MAF.
Added about 30 oz of techron Complete fuel system cleaner to the already full tank, sadly it is only 87 in the tank currently. Will run it down to the gas light, refill with premium, run it to the gas light. Refill again with Premium and another 30 oz of Techron fuel system cleaner.
Had the Negative battery cable pulled for the entire time. So of course is sputtered the first start attempt and then fired right up. Between yesterday afternoon and this morning we have driven over 120 miles of mostly town traffic and the MPG indicator is at 14.4. I usually only see that high on the highway on extended trips. No CEL, No detectable Misfires. Hope to see the MPG continue on the current course. Definitely a +/-10%ish improvement. Will see on next 300 mile NC drive for Highway MPG.
