99 4.0 Ranger CEL loss of power low gas mileage
#1
02-20-2010, 04:32 PM
Join Date: Nov 2008
Location: Dekalb, IL
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99 4.0 Ranger CEL loss of power low gas mileage
Thanks again everyone on this site for what appears to be a successful fix.
Special thanks to Rockledge and KaiserM715
My wife’s 1999 Ford Ranger 4.0 V6 auto trans 4x4 110,000 miles was occasionally tripping the CEL and she was experiences low gas mileage around 10mpg (she use to get about 15mpg) and loss of power. When I scanned it I had codes P0171 Bank 1 lean and P0174 Bank 2 lean. I originally looked for vacuum leaks spraying starter spray everywhere along the vacuum lines and all around the intake without any reaction. I would clear the codes and within a few weeks the CEL would come back on with the same codes. At this time I logged onto FTE and started searching for help. Luckily I stumbled across several good threads that explained that my problem was most likely old, hard, upper intake o-rings that are making a poor seal to fuel manifold.
See thread : https://www.ford-trucks.com/forums/9...and-p0174.html
That thread references a thread from another website which is the instructions that I followed: How to replace upper intake manifold gaskets - Ford Explorer Ranger Enthusiasts "Serious Explorations"®
The instructions don’t mention the location numbers on the coilpack or engine so here they are( I seen a thread on here that have the coilpack wrong:
Engine
P
A 3 6
S 2 5
S 1 4
Front
Coilpack
P
A 3 4
S 2 6
S 1 5
front
I only changed the upper intake o-ring seals, but while the upper was off I re-torqued the fuel manifold (11lb-ft) as well as the lower intake (12lb-ft). These were both less than the spec and could have also been causing some leakage. BTW I was able to purchase the E7 Torx bit required for the fuel manifold at AutoZone.
By doing only this I no longer got the CEL with the two lean codes and I was getting just under 14MPG. Unfortunately the power was still lacking at higher RPMs and I was hoping for more MPG so I extended the fix to include cleaning the MAF, replacing the PCB valve, replacing the air filter, and replacing the fuel filter.
Clean MAF meter
https://www.ford-trucks.com/forums/1...-cleaning.html
The wires on my MAF meter did not look dirty, but I figured I bought the MAF meter cleaner so I should use it. I blasted the wires three times from all directions with a ten minute drying off period in-between rounds. I did not touch the wires with anything other than the spray.
PCV valve
My PCB valve was a standard replacement part found out AutoZone. It was the type that pushed into a hole in the driver’s side valve cover and a vacuum line from the upper intake attaches to it. I see some other discussion of different types and places for PCV valves so I thought I would add my data point for my year and engine. I shook it and it appeared good, but I replaced it anyways.
Fuel filter
Mine was located on the driver side, below the door on the inside of the frame rail. I had to remove a skid plate that was held on by four bolts in order to get better access to it. When I took it off tons of gunk came out the gas tank side. This was the dirtiest fuel filter I have dealt with since I worked on my 66 stang that had sat 15 years before I brought it back to life.
Air filter
I went with a cheapy Fram that I bought at Farm and Fleet (they didn’t have stock of the Motorcraft one). The one I took out was very dirty packed with bugs, leaves, and dirt.
After cleaning the MAF, replacing the PCB valve, replacing the air filter, and replacing the fuel filter; the truck seems to be accelerating better and has more power at high RPMs. I’ll see how the gas mileage goes after a few weeks.
I took some pictures and will try make time to load them onto photobucket in case some people like me need visual aids
Special thanks to Rockledge and KaiserM715
My wife’s 1999 Ford Ranger 4.0 V6 auto trans 4x4 110,000 miles was occasionally tripping the CEL and she was experiences low gas mileage around 10mpg (she use to get about 15mpg) and loss of power. When I scanned it I had codes P0171 Bank 1 lean and P0174 Bank 2 lean. I originally looked for vacuum leaks spraying starter spray everywhere along the vacuum lines and all around the intake without any reaction. I would clear the codes and within a few weeks the CEL would come back on with the same codes. At this time I logged onto FTE and started searching for help. Luckily I stumbled across several good threads that explained that my problem was most likely old, hard, upper intake o-rings that are making a poor seal to fuel manifold.
See thread : https://www.ford-trucks.com/forums/9...and-p0174.html
That thread references a thread from another website which is the instructions that I followed: How to replace upper intake manifold gaskets - Ford Explorer Ranger Enthusiasts "Serious Explorations"®
The instructions don’t mention the location numbers on the coilpack or engine so here they are( I seen a thread on here that have the coilpack wrong:
Engine
P
A 3 6
S 2 5
S 1 4
Front
Coilpack
P
A 3 4
S 2 6
S 1 5
front
I only changed the upper intake o-ring seals, but while the upper was off I re-torqued the fuel manifold (11lb-ft) as well as the lower intake (12lb-ft). These were both less than the spec and could have also been causing some leakage. BTW I was able to purchase the E7 Torx bit required for the fuel manifold at AutoZone.
By doing only this I no longer got the CEL with the two lean codes and I was getting just under 14MPG. Unfortunately the power was still lacking at higher RPMs and I was hoping for more MPG so I extended the fix to include cleaning the MAF, replacing the PCB valve, replacing the air filter, and replacing the fuel filter.
Clean MAF meter
https://www.ford-trucks.com/forums/1...-cleaning.html
The wires on my MAF meter did not look dirty, but I figured I bought the MAF meter cleaner so I should use it. I blasted the wires three times from all directions with a ten minute drying off period in-between rounds. I did not touch the wires with anything other than the spray.
PCV valve
My PCB valve was a standard replacement part found out AutoZone. It was the type that pushed into a hole in the driver’s side valve cover and a vacuum line from the upper intake attaches to it. I see some other discussion of different types and places for PCV valves so I thought I would add my data point for my year and engine. I shook it and it appeared good, but I replaced it anyways.
Fuel filter
Mine was located on the driver side, below the door on the inside of the frame rail. I had to remove a skid plate that was held on by four bolts in order to get better access to it. When I took it off tons of gunk came out the gas tank side. This was the dirtiest fuel filter I have dealt with since I worked on my 66 stang that had sat 15 years before I brought it back to life.
Air filter
I went with a cheapy Fram that I bought at Farm and Fleet (they didn’t have stock of the Motorcraft one). The one I took out was very dirty packed with bugs, leaves, and dirt.
After cleaning the MAF, replacing the PCB valve, replacing the air filter, and replacing the fuel filter; the truck seems to be accelerating better and has more power at high RPMs. I’ll see how the gas mileage goes after a few weeks.
I took some pictures and will try make time to load them onto photobucket in case some people like me need visual aids
#2
02-20-2010, 08:51 PM
#3
02-21-2010, 02:44 PM
Join Date: Nov 2008
Location: Dekalb, IL
Posts: 27
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I prob should have, but a pulled a few of the easy plugs and they looked good. I think I will wait for summer for new plugs and wires if the truck continues to behave itself. If not I'll be back out in the garage next weekend.
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