Members I just performed a timely tune up to my 1998 5.4l Expedition. I changed the plugs with Motor craft platinum plugs like factory and a set of Summit performance coils. I replaced all 8. The truck starts fine and idles fine. When driving over 55ph the motor will shake and hesitate at times. It seems worse while rounding turns. I am not receiving any engine lights. It has a clean air filter and had the fuel filter changed out a few months ago. I have checked and I have no loose harness connections or vacuum lines. What could cause my issue. Your help is very appreciated.
Issues after a tune up
- Thread starter BroncoTim
- Start date
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CaperCanadian
Full Access Members
Sounds to me like it might be a bad coil. Even though you replaced them one of the new ones might be bad.
NickChick
Member
Check your COP connectors. I had the same problem for a while and it bugged the crap out of me until I found out one of my COP connectors wasn't plugged in completely causing it to make some contact but not enough making an intermittent missfire.
98EXPnSRQ
Full Access Members
Vacuum check your egr valve and see if the idle drops and stumbles when you put vacuum to it at idle.
Thanks
I have bought a new Summit coil as the rear passenger coil appeared to have a brown substance on the top. The other coils did not have it. Maybe that coil s bad? I will replace it this weekend. This will be fun as its the hardest one to gain access to. Thanks for the advice on the COP connectors and EGR test thoughts. I will check both of them. I will give feedback after this weekend after everything is complete and let you know if the problem is resolved.
I have bought a new Summit coil as the rear passenger coil appeared to have a brown substance on the top. The other coils did not have it. Maybe that coil s bad? I will replace it this weekend. This will be fun as its the hardest one to gain access to. Thanks for the advice on the COP connectors and EGR test thoughts. I will check both of them. I will give feedback after this weekend after everything is complete and let you know if the problem is resolved.
Bedrck47
Full Access Members
use a little bit of dialectic grease on the contact points of the connectors
I removed the suspect coil and found brown stuff oozing out of it and a small crack in the top. This was a new coil. I replaced it with a new one. I made sure all the COP connectors had dielectric grease and were secure. Started it with no issues. I have drove the expedition 200 miles this weekend with no issues. Glad to see this problem resolved. Thanks for all of the help.
Bedrck47
Full Access Members
Thanks for the update
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