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I have a 2004 f150 triton 4X4. The engine misses (I guess) hard at around 1700 RPM under a load. No check engine lights, no codes that I've been able to capture. Usually runs fine otherwise, although sometimes seems to idle at barely 500 and will stall. Restart clears condition.
When the (missing?) hits, it hits hard. Almost feels like the the crankshaft is stopping for a split second...
The most likely part that causes misfires on this vehicle is the ignition coils. There is a coil on each spark plug. Do you know if your mechanics scan tool has access to mode 6 data? Ford vehicles take awhile to set a misfire code, but mode 6 data will indicate if any cylinders have misfired. They should also be able to monitor the power balance and see if there is a misfire taking place and which cylinder is misfiring. Since there are 8 ignition coils it would be very expensive to just start replacing them.
Don't know about mode 6 data. I have an
I have an Actron code reader like this. I've been keeping it plugged into the port. It's not logged any codes.
I read the information from the link you sent and it will not read data or misfires. From what I read the only information it will give you is if a code sets. Once a code sets it will give you freeze frame data which is a couple of parameters of data like rpm, coolant temp etc. It will not read mode 6 data and it will not show misfire data. Unfortunatly the only thing it will do is give you information once the code is set. As I said misfire codes take a while to set. The computer has to see a certain amount of misfires within a set amount of time. If the coil or plug was completely not working it would set it fairly quick, but since it is intermittent it may not ever set a code.
Ok, so I'm planning on taking the vehicle to a mechanic. I just wanted to be informed before doing that so I can ask questions. Would you recommend taking the truck to the dealer? Also, the truck is at 120K miles on the original plugs, coils, etc. Should I replace it all? What do you think I should expect to pay for the work?
I would suggest finding someone that at least has the Ford IDS scan tool. It will pick up more information than some of the others. A Ford dealer ship should have this and some independent dealers will have it. Make some phone calls and ask if they have the IDS. At 120,000 miles the spark plugs definitely should be replaced. The coils should only be replaced if needed. If you have any mechanical ability you may be able to change the spark plugs and coils yourself if you are wanting to replace them all. Do you know which engine is in your truck?
If it is the 5.4 liter the spark plugs fro Ford are $19.16 a piece, The ignition coils are $83.64 a piece and the labor to do it is 2.8 hours.
Will the shop be able to determine which coils need to be replaced?
Yes it is but the spark plugs should definitely be done. These spark plugs are assembled from three different pieces and sometimes come apart when removing. If this happens you need special tools in order to completely remove them. I have never had it happen, but Ford had a video out on the correct procedure to remove them.
They should with the aid of the IDS to pinpoint which cylinder is misfiring.
OK thanks. Can you think of any other possible sources for this issue? It seems pretty obvious at this point based on your description of the plugs and coils.
In my experience this is the the ignition coils are the causes of misfires, but it is definitely time for the spark plugs. The only other thing I can think of is the fuel injectors, but I have never replaced any of them on this engine.
Ok thanks for the advice!