Knock Knock
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Freshman User
Joined: Feb 2009
Posts: 48
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From: American Samoa
Knock Knock
Please don't say the obvious...
I have a situation with a Fully loaded 2008 F-150, 5.4, FX4.
The problem is that the vehicle has a spark knock that is very pronounced at between 1400 – 1800 RPM under a medium load. I have experienced it heading up a relatively steep incline in first gear with very little weight in the vehicle. The knock was pronounced and continuous if this rev range was maintained. This fault has been on and off for the last couple of months but seems to be getting worse in recent weeks. We have done extensive testing with no fault codes being displayed –
1. Baro PID – 99.06 KPa .
2. Fuel Press – 301 KPa
3. Power Balance – excellent
4. Relative Compression – excellent (cyl 3 down by only 1%)
5. PCM has the Latest Calibration
Has anyone ever come across this? Is it a normal condition/characteristic of this vehicle? Has anyone had success with a de-carbonizing agent that is compatible with the converter and O2 sensors?
Any help would be much appreciated.
Kiwi.
I have a situation with a Fully loaded 2008 F-150, 5.4, FX4.
The problem is that the vehicle has a spark knock that is very pronounced at between 1400 – 1800 RPM under a medium load. I have experienced it heading up a relatively steep incline in first gear with very little weight in the vehicle. The knock was pronounced and continuous if this rev range was maintained. This fault has been on and off for the last couple of months but seems to be getting worse in recent weeks. We have done extensive testing with no fault codes being displayed –
1. Baro PID – 99.06 KPa .
2. Fuel Press – 301 KPa
3. Power Balance – excellent
4. Relative Compression – excellent (cyl 3 down by only 1%)
5. PCM has the Latest Calibration
Has anyone ever come across this? Is it a normal condition/characteristic of this vehicle? Has anyone had success with a de-carbonizing agent that is compatible with the converter and O2 sensors?
Any help would be much appreciated.
Kiwi.
Thread Starter
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Freshman User
Joined: Feb 2009
Posts: 48
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From: American Samoa
We are the Dealers... in American Samoa - a little island in the middle of the pacific ocean... of few resources...
we have scanned the vehicle many times and scoped all of the sensors, including the o2 sensors and all is checking out perfectly. We have sent a help request to the hotline but sometimes it takes days to get us an answer...
I thought that some of you blokes may have a tried and tested method or fallen across the fix for this problem. I have been putting it down to poor fuel but 104 octane boost hasn't even solved the problem... I have searched the site for fuel or spark knock faults but nothing seems to fit. Any help would be appreciated,... Kiwi.
we have scanned the vehicle many times and scoped all of the sensors, including the o2 sensors and all is checking out perfectly. We have sent a help request to the hotline but sometimes it takes days to get us an answer...
I thought that some of you blokes may have a tried and tested method or fallen across the fix for this problem. I have been putting it down to poor fuel but 104 octane boost hasn't even solved the problem... I have searched the site for fuel or spark knock faults but nothing seems to fit. Any help would be appreciated,... Kiwi.
Senior User
Joined: Jun 2005
Posts: 375
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Never had much faith in over the counter octane boosters. Engine has knock sensors to modify timing according to fuel, to a extent. Engine should ping the least in low gears, ping usually occurs in higher gear at low RPM when engine is pulling the hardest.
Thread Starter
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Freshman User
Joined: Feb 2009
Posts: 48
Likes: 0
From: American Samoa
Thanks Tylus - that is what i've been putting it down to as well. The other thing that i want to do is decarb the engine. We have a speed limit of only 25mph so with poor fuels and no real rpm or load i'm wondering if a decarb would be beneficial. Appreciate your opinion. Thanks
Kiwi
Kiwi
Senior User
Joined: May 2009
Posts: 137
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How about oil? could oil that was to thick or thin effect the operation of hydraulic lifters enough to make a knock? carbon on the valves would do the same right? I'm not sure I've ever heard spark knock in a newer engine but I know out 04 and 05 both had the cam-phaser knock by 12,000 miles. the phaser update fixed each.
