• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

1986 2.9 Horrible Fuel Mileage!!!


Flat_Bottom

New Member
Joined
Aug 30, 2015
Messages
15
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Transmission
Automatic
OK, so let me start by a quick truck history: It sat for 8 years, guy couldn't get it to run. I buy it and find the HP pump is stuck and wont rotate. Couple whacks with a screw driver and it spit and sputtered fuel out, hooked it up and she fired right up. Went ahead and did that following:
-Removed fuel tank, scrubbed and cleaned
-New intank pump and sending unit
-New HP Pump
-New fuel filters

Took it down and she barely passed California smog by a 1 digit margin (BTW, it always had a noticeable miss even when getting smogged). 2 days later the truck starts running noticeably worse and worse (drove a couple miles a day to keep it going, was not a daily driver) and then to the point one day the truck would shutter and barely run. So, since smog guy said my cat was almost toast, I went ahead and done the following:
-New catalytic converter and exhaust system
-New o2 sensor
-New cap, rotor, coil, plugs and wires
-New TPS, MAP, EGR sensor
-Removed and cleaned IAT sensor
-reset timing to 10* (I did it correctly)
-New fuel pressure regulator since old one was leaking into vacuum.

Truck then ran worse than ever, chugging blackish smoke and got a best MPG of 8.02. Found the regulator was defective and replaced again (no more issues) and now its up to 12.64 mpg (101.2 miles, used 8.009 gallons). Shifts great, runs super smooth, has no power for a v6 whatsoever, I usually drive around in 3rd because it just cant pull in 4th with converter locked up. Please help because I am about to sell it. I wont have crappy fuel mileage and no power. Please, any help is appreciated.
 


Flat_Bottom

New Member
Joined
Aug 30, 2015
Messages
15
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Transmission
Automatic
Also, truck is bone stock with 235/75/15 Federals with a lock rite in the rear with 3:73 gears. 70 mph on freeway with converter locked in 4th is right at 2200 rpms. Same speed in 3rd is 28-2900 rpms. I have ran this last tank ONLY in 3rd gear and have driven it no harder or softer and thus far am seeing better results. Will post those tomorrow when I top it off again.
 

kimcrwbr1

Well-Known Member
Joined
Dec 6, 2009
Messages
6,044
Reaction score
46
Points
48
Location
maplevalley WA
Vehicle Year
1983
Make / Model
ford
Engine Size
2.8l
Transmission
Automatic
Did you reset the computer after installing the sensers? Disconnect the battery for at least 1/2 an hour and confirm all the vacuum lines are soft and tight. Pull all electrical connectors apart and clean with electrical cleaner. You can pull the codes with a test light or code reader. Disconect the egr vacuum and plug the line and see if it idles any better. If not while its running connect manifold vacuum up to the egr the engine should stall.
 

Flat_Bottom

New Member
Joined
Aug 30, 2015
Messages
15
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Transmission
Automatic
Yes, I let the truck sit for a little over an hour once all the sensors were replaced. I just purchased a code reader and I was getting the fault for TPS out of range, which is why I tested and reset my idle. Closed throttle the TPS is at .88vdc and WOT is 4.71vdc. The other code was for the EGR, which I found the pipe nut had backed itself out. I tightened it back up and fired the truck up, removed vacuum line from EGR and reinstalled, the truck didn't die but stumbled real bad like it was then came back to idle. I will check all my codes again, but the truck is running flawless, just super crappy fuel mileage. I can deal with the immense lack of power if I got decent fuel mileage but I am currently getting the worst of both worlds. All electrical connections have been checked, also forgot to add to original post that the ECM is brand new and so are the injectors.
 

Flat_Bottom

New Member
Joined
Aug 30, 2015
Messages
15
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Transmission
Automatic
So after driving it around in 3rd only with mainly freeway driving between 65-75 mph, I have done a little better with the fuel mileage. I will be filling it back up after work tonight but already I have gone 115 miles and not quite on a quarter tank comparted to 101 miles and I was just below a quarter. Will have numbers in a few more hours. Also will be pulling codes again in the morning. I reset the computer, again, and wanted to put some miles on it before checking it again. I also noticed that the brand new fuel regulator blew through its diaphragm so I have the line removed and pinched at the moment. The truck smoothed out tremendously when I don't this and runs like a new truck, still with crap fuel mileage and no more power than what was there but hopefully with the another new regulator it will help it out. This will be the fourth regulator in 2 months that I have had to replace...not sure whats going on with that. Also noticed a surging when in the higher RPMs, like over 3k. Not sure if this has anything to do with the added fuel pressure from the regulator vacuum being bypassed or not.
 

truckerdawg

Member
Article Contributor
U.S. Military - Veteran
Joined
Feb 25, 2010
Messages
130
Reaction score
5
Points
18
Location
GA via NC Mtns.
Vehicle Year
1990
Make / Model
ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Total Lift
4"
Tire Size
31X10.50
Run a compression check on each cylinder.
 

Flat_Bottom

New Member
Joined
Aug 30, 2015
Messages
15
Reaction score
0
Points
0
Vehicle Year
1986
Make / Model
Ford
Transmission
Automatic
A compression test is my next step. I just need to go get a gauge to do it. If it all checks out good then I think it will be time to pass it on and get a 4.0 truck.
 

Hunter71601

New Member
Joined
Dec 22, 2014
Messages
21
Reaction score
0
Points
0
Location
Maryland
Vehicle Year
1988
Make / Model
Ford
Engine Size
2.9
Transmission
Automatic
i'm now on my 2nd regulator in 3 months before it blew truck ran fine ???
 

Sponsored Ad


Sponsored Ad

Members online

Today's birthdays

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Shran
April Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top