Howdy everyone
My mom has a 1999 FordExplorer with the 4.0L SOHC
At idle and while engine is cold, It will run smooth, gas peddle is a little laggy, But the ride has 160,000 miles.
After a 10-15 minute warm up, once engine is at running temp. Idle is fine. The second you hit the throttle its like you have no power. It will spit, Sputter and bog down.
I just completed a tune up. Giving it E3 Plugs and Wires. Though i have not changed the passenger side very back plug yet. Still trying to figure that one out. The plugs were not in bad shape so i dont think that is the issue.
My friend brought over his Snap-On Scanner. It is throwing codes for the O2 Senros.
Everyone i talked to said it was a CAT issue. So i removed the cat's and threw in some flex pipe to test and figure out the issue.
One cat was really bad, other was in ok shape.
THe only other code it was throwing was a Mass Air-flow.
I changed that out.
Truck is still doing the same thing. I dont want to keep throwing parts at it and getting the same results... I was thinking tonight of cleaning the EGR to see if that would help.
Anyone else have any ideas?

 

Ok, lets start at the basics.

We have hesitation and throttle response issues.

You just completed a tune up and put on new plugs and wires. Lets start there. Take the junk E3s and the wires you bought and throw them in the trash. Those parts can and do cause some of the issues you are experiencing. Use only OEM spec wires (Motorcraft or Magnacore), and OEM spec plugs double platinum or finewire iridium (Motorcraft, Autolite, NGK).

Your buddy came over with a scanner. He apparently doesn't know how to use it. What are the actual codes. We cannot help you in that area without knowing the actual codes.

A cat issue would cause low power all the time. Throttle response is not a cat issue. Cat failure is a symptom of things running like crap. Running without cats is not likely to help you diagnose the problem, because your cam is set up for cats and the cylinders get over scavenged, which messes with sensor readings.

You replaced the MAF with what brand? Motorcraft only. Anything else can be as bad or worse than the old one you took out.

Your story goes beyond codes, and from your description, you have NOT done a full tune up, and the vehicle has not been properly diagnosed. A full tune up would include new O2 sensors (you are overdue), new fuel filter, new air filter, clean throttle body, decarbon the engine, etc.

 

Could this be a crank position sensor issue?

I have 223K on my orginal Cats. I don't think that was really the issue here either.

 

Intake o-rings would be a suspect. A common and recurring problem on these engines. They will cause a lean code, then poor running like the OP describes.

No guarantee that's it, as who knows what the codes were, or what they will be now without cats.

 

Throttle Position Sensor would cause those symptoms. Check connections.

 

Welcome to the forum!

I want to get confirmation that the sequence in your post above is the order things happened as well. Specifically, you replaced plugs and wires to try to solve the lack of power versus the lack of power starting after your replaced the plugs and wires.

As for the passenger rear spark plug, if you have a variety of extensions and a proper spark plug socket, that one is not too bad to replace from the passenger wheel well, especially when the truck is jacked up slightly, properly supported with a jack stand, and wheel removed.

-Rod