Tune Up - 1998 Exped XLT 4WD

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Machete

My Rig. 2000 EB 4x4 5.4L
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Air filter was delivered today :) The $100 I spent is an investment, really. I'll pick up the MAF and throttle sprays!!
The Lariat HAS to have a Master Cylinder, also delivered, before she can go anywhere. No brakes at all. Nada. Kinda scary. Pedal to floor and coast to stop. Also got her a solenoid and battery cables at my mechanic's suggestion because even with a fresh battery, she won't give the slightest effort to start. crickets.
Thank you all for the help ... Dr's appointments tomorrow, fix the mower Wednesday, work on garage organization and maybe ready to install parts over the weekend!!

...don’t forget frying the bacon!
 

Jim Brown

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Since it has been 8 yrs since maint it may require more work. If the engine is still running rough after you perform basic maint "tune-up" (replace plugs, plug boots, air cleaner, fuel filter, and clean MAF, throttle body, IAC valve, repairs to get rid of any error codes), there's more you can do yourself before paying a mechanic. Consider buying your own inexpensive code reader to diagnose problems. Autel AL319 is about $40 and it will read live data from your engine's computer, and save you a ton of money in labor costs and fuel economy if you want to repair it yourself.

Following is probably more info than you wanted, but if you want to DIY and it has been a long time since maintenance, it may come in handy later.

Look at live data: long term fuel trim (LTFT) and short term fuel trim (STFT). LTFT at steady rpm should be around 0.0%, but could be +-25% before the computer reports an error code. If LTFT is more than +-10% it's worth looking for a problem. At steady rpm, closer to zero is better. Better than LTFT +-3.0% and STFT +-6.0% is pretty good.

Don't worry so much about the exact numbers, just see if they're a long way from 0.0%, and if they're positive or negative. Positive means the computer is providing a lean fuel mixture. Negative means it's providing a rich fuel mixture. Also, look if there's a difference between Bank 1 (passenger side) and Bank 2 (driver's side). This lets you know which side the problem is on.

Here's a list of causes for running too lean (positive LTFT) or rich (negative LTFT).

Running too lean –High positive fuel corrections can be traced to MAF and O2 sensor faults, vacuum leaks from intake gaskets/hoses, un-metered air (intake snorkel leak), clogged or dirty fuel injectors, fuel delivery issues, and exhaust restrictions such as a clogged catalytic converter.

Running too rich –High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and base engine issues such as low compression and incorrect camshaft timing.

You can further search/ discuss each cause later if needed.

Finally, I recommend looking at fuel trim before and after all basic maintenance. It lets you know how much improvement you gained at each stage of repairs. You can search 'long term fuel trim' and get a whole lot more info if you like. Good luck!
 
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