Rough idle
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Joined: Dec 2022
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You are a 2005 4.2. I do not have first hand experience with the 4.2 but in general the EGR tube end fittings (nut and threads) corrode/rust badly over time. My experience with EGR tubes has always been trouble. Michigan vehicles. The end fittings don't want to turn but assuming you are able to turn the nuts here is what I would do to lessen or eliminate the leak you detected.
Remove the tube from the truck and clean the threaded areas where it attaches to the exhaust manifold and egr valve with a wire brush and in extreme cases a triangular needle file. Clean the internal threads with a wire brush and air blow clean. Once the external threads are cleaned on the exhaust manifold, install nut and tighten by hand. Take a small hammer and tap on nut as you work it back and forth on the threads with the intent of making clockwise progress by knocking rust and debris from the threads. Eventually nut will progress and a wrench will be required to work it back and forth. Once you are satisfied that nut moves freely go to the EGR valve and repeat same procedure being carefully not to damage EGR valve. When you are satisfied with results apply a medium coat of "never-seeze" to the threaded connection and tighten both nuts securely. If leak is still present tighten further until leak is eliminated. In some extreme cases nuts had to be ground off with a cutting wheel and the egr tube had to be replaced.
These are my thought to help resolve the leak at the EGR valve tubing.
Remove the tube from the truck and clean the threaded areas where it attaches to the exhaust manifold and egr valve with a wire brush and in extreme cases a triangular needle file. Clean the internal threads with a wire brush and air blow clean. Once the external threads are cleaned on the exhaust manifold, install nut and tighten by hand. Take a small hammer and tap on nut as you work it back and forth on the threads with the intent of making clockwise progress by knocking rust and debris from the threads. Eventually nut will progress and a wrench will be required to work it back and forth. Once you are satisfied that nut moves freely go to the EGR valve and repeat same procedure being carefully not to damage EGR valve. When you are satisfied with results apply a medium coat of "never-seeze" to the threaded connection and tighten both nuts securely. If leak is still present tighten further until leak is eliminated. In some extreme cases nuts had to be ground off with a cutting wheel and the egr tube had to be replaced.
These are my thought to help resolve the leak at the EGR valve tubing.
I ran another smoke test via the intake, here's what I found. No other leaks detected, same spot, same leak. I replaced the egr valve and gasket. Gonna run evap smoke test next. I also have a new Motorcraft fuel injection pressure sensor on the way, should be here today. My mechanic friend said that it sounds like a weak or failing fuel pump, but u figured that I'd try the sensor first.
EGR valve, to tube off of intake manifold, leak. Very minute, but still present.
2004 F150 5.4 Lariat
Joined: Dec 2012
Posts: 956
Likes: 156
From: Summerville, SC
Some additional thoughts:
- You probably looked, but if you haven't, look carefully for a vacuum leak behind the engine, behind the battery and between battery and fender the next time you smoke test. Also shut off vacuum to the purge valve on its bottom hose. Further, put the intake air assembly back on before testing.
- IMHO you really need Forscan (it's free). It could probably have saved you a lot more than you’ve already spent, plus you’ll have it for future problems. If you decide to use it, make sure to buy one of the OBD tools recommended on their web site, and to ask for their free extended license.
