Any ideas where to start looking?
I have a 2005 Ford Expedition 5.4 XLT. It really does drive good and I dont necessiarly feel a loss of power however I notice that when Im driving locally and on the highway between 40-60 mph I get this RPM drop and the gas peddle feels less responsive. Ill be driving and the only way to get the rpm back up to normal is to floor the gas. Its not low enough that it feels like its gonna stall but it goes back to almost idle rpm. It idles perfectly fine, engine is not shaking or misfiring. It DOSENT do this when Im in cruise controll; only when Im manually pressing the peddle. Any idea what this could be? It shifs perfectly fine, no slipping or jerking. Any help is apperciated. I looked at the air filter and recently cleaned the throttle body and MAF to try and solve the issue but no luck.
- CactiJoeLv 61 month ago
Could be oil pressure is dropping when it gets hot or the catalytic converter is slightly plugged up which would limit exhaust flow. You could try pouring a bottle of STP in the engine and see if that has any effect. Oil pressure does drop as an engine wears internally and can get to a point where it's too low to maintain a respectable oil film on the cylinder walls. Might do 10W30 or 10W40 in the summer months if you think this is the issue.
- thebax2006Lv 72 months ago
Try putting it in the next lower shift lever position when you're going at that speed range.
You need a mechanic scan tool that can read the engine data and transmission data while driving.
OBD II code readers don't read transmission codes so that's something to consider.
If the ABS/traction control light is on that can cut engine power while driving. If that's happening you need an ABS capable scan tool to determine if there is a bad wheel speed senor.Source(s): Mitsubishi Master Tech
- Anonymous2 months ago
Sounds like a bad TPS. Try replacing it. Check the connector on the TPS too. A dirty EGR valve could be causing it too. Good luck.
- DanLv 52 months ago
Stop looking at the tach. If the truck is going the speed you want the transmission is simply doing it's job and shifting up to keep revs down.
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- JetDocLv 72 months ago
The transmission has dropped into overdrive and reduced the engine RPM to save on fuel consumption. If it ain't broke, DON'T FIX IT!