My 89 2.9 4x4 with 31x10.50 tires is a pig! I can go 180 miles driving real nice and no wheeling on 14.3 ish gallons! I took a ride in my buddy's Subaru loyal with a 1.8 opposed 4 motor and it throws you into the seat compared to my 2.9 ranger.... I was getting 120 miles to 14.5 gallons before I removed the cats. I drive nice too but I kinda have to drive hard to get up to speed or people tail gate me and I don't blame them. So far my truck has has new plugs, wires, cap & rotor, fuel filter, air filter, delo 15w40 oil & wix filter. My exhaust system is just a glass pack and a tip out the side so no restrictions or anything and I'm running a 2.5 inch system. I also installed a electric fan but have yet to see what it helps as I haven't had to fill up yet since the install. Another thing is at like 3500 rpm I feel what I like to call the "boost" kick in and it goes better I'm assuming that's the timing advance kicking in and it is more noticeable when its still not up to temp but warmed up enough to get on it (I'm nice to my truck when she's cold). Can I advance the timing to 12 degrees and have that help? Is it just my tires sucking my gas? I also do allot of short trips I rarely go on long rides in my truck. My average trip is probably like 3-5 miles if that don't help
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2.9 sucking gas and slow!!
- Thread starter 89-4x4
- Start date
- Joined
- Apr 13, 2009
- Messages
- 15,131
- Vehicle Year
- '06, '11
- Engine
- 3.0 V6
- Transmission
- Automatic
Nice looking truck.
How many miles on the truck?
Last time you changed the o2 sensors? They get tired too.
What gears do you have? I suspect tire size will have a lot to do with your gas use. I use 4.10 with 31" tires and get about 14 mpg[us] in my b-2 [tired motor]. I'm getting about 14 mpg[us] in my 2.9/auto Ranger with stock tires. Its tired too with 300,000 Km.
Unless your cats were plugged removing them did nothing.
Richard
How many miles on the truck?
Last time you changed the o2 sensors? They get tired too.
What gears do you have? I suspect tire size will have a lot to do with your gas use. I use 4.10 with 31" tires and get about 14 mpg[us] in my b-2 [tired motor]. I'm getting about 14 mpg[us] in my 2.9/auto Ranger with stock tires. Its tired too with 300,000 Km.
Unless your cats were plugged removing them did nothing.
Richard
Truck has 191k US miles and doesn't use and oil or anything. I haven't done the o2 sensor and it looks older too. Yes the cats were plugged up bad it was getting 8-9mpg with the cats still on, now with the 2.5 inch glasspack I get 14.5 mpg. My truck surges sometimes when I stop too and sometimes it surges low enough to twitch the oil pressure gauge. I also want to know what the "boost" I''m felling is in the first 3 miles of driving it, At 3k rpm it all the sudden throws your head into the seat then again at 4k rpm even harder it throws my head into the seat harder so maybe the timing is too retarded?
What do the spark plug tips tell you?
lean/rich, normal
It reads like you are running rich, from the MPG, of course, but also the comments about unexpected power when throttle plate is opened more, air/fuel mix gets to correct leaner mix.
First stop is always the fuel pressure regulator(FPR) on the fuel rail, it will have a vacuum line attached, check this line for fuel or fuel smell.
FPR diaphragm can crack and fuel is sucked into engine causing a richer mix.
The 1989 2.9l has a MAP sensor I think, it will be located on the firewall passenger side behind the wiring.
It will have a 3 wire connector and a vacuum line, remove the vacuum line and check it for cracks, make sure it can hold pressure.
Also check connector contacts.
The MAP sensor reports intake vacuum pressure to the computer, the computer uses this info to base air/fuel mix ratio.
O2 sensors can only be used after engine warms up, they need to be at 650degF or hotter to work correctly, so cold engine start wouldn't see O2's being used for at least 5 minutes, warm engine starts are delayed about 1 minute, computer uses a timer.
The fact that the Cats were collapsed could mean a rich mix for awhile which could foul the O2 sensors as well.
O2 sensors tend to fail "lean" so computer would run engine richer than needed based on older O2 sensors that are failing.
The O2 sensors use a chemical reaction to detect Oxygen levels so they do simply wear out when the chemicals are gone.
On a side note, my 4.0l was running rich, I found one of my O2 sensors was coming unscrewed, so air was being sucked in causing a higher O level, which computer corrected by running richer.
FYI about exhaust systems, best exhaust systems create a "velocity" at the manifold pipes, this velocity actually lowers the pressure at the exhaust valves, so exhaust is pulled out when valve is opening.
This velocity is created by using smaller pipe into a larger pipe(collector), as the smaller pipes exhaust is dumped into the collector it's pressure drops, which drops the pressure in the other smaller pipes on the collector, like a suction effect.
This is where the "back pressure" myth comes from, people put on larger exhaust pipes and got lower performance????
"Engine must like smaller exhaust pipes so wants some back pressure" << the myth
The larger exhaust pipes lowered the "velocity" so increased the pressure at the valves!
This is where header design comes in, and it's above my pay grade
But the creation of more or less velocity in the exhaust system can give more or less power in certain RPM ranges.
This could also be why you feel the power difference only at higher RPMs, the velocity in exhaust system lowers the pressure at the valves only at higher RPMs
lean/rich, normal
It reads like you are running rich, from the MPG, of course, but also the comments about unexpected power when throttle plate is opened more, air/fuel mix gets to correct leaner mix.
First stop is always the fuel pressure regulator(FPR) on the fuel rail, it will have a vacuum line attached, check this line for fuel or fuel smell.
FPR diaphragm can crack and fuel is sucked into engine causing a richer mix.
The 1989 2.9l has a MAP sensor I think, it will be located on the firewall passenger side behind the wiring.
It will have a 3 wire connector and a vacuum line, remove the vacuum line and check it for cracks, make sure it can hold pressure.
Also check connector contacts.
The MAP sensor reports intake vacuum pressure to the computer, the computer uses this info to base air/fuel mix ratio.
O2 sensors can only be used after engine warms up, they need to be at 650degF or hotter to work correctly, so cold engine start wouldn't see O2's being used for at least 5 minutes, warm engine starts are delayed about 1 minute, computer uses a timer.
The fact that the Cats were collapsed could mean a rich mix for awhile which could foul the O2 sensors as well.
O2 sensors tend to fail "lean" so computer would run engine richer than needed based on older O2 sensors that are failing.
The O2 sensors use a chemical reaction to detect Oxygen levels so they do simply wear out when the chemicals are gone.
On a side note, my 4.0l was running rich, I found one of my O2 sensors was coming unscrewed, so air was being sucked in causing a higher O level, which computer corrected by running richer.
FYI about exhaust systems, best exhaust systems create a "velocity" at the manifold pipes, this velocity actually lowers the pressure at the exhaust valves, so exhaust is pulled out when valve is opening.
This velocity is created by using smaller pipe into a larger pipe(collector), as the smaller pipes exhaust is dumped into the collector it's pressure drops, which drops the pressure in the other smaller pipes on the collector, like a suction effect.
This is where the "back pressure" myth comes from, people put on larger exhaust pipes and got lower performance????
"Engine must like smaller exhaust pipes so wants some back pressure" << the myth
The larger exhaust pipes lowered the "velocity" so increased the pressure at the valves!
This is where header design comes in, and it's above my pay grade
But the creation of more or less velocity in the exhaust system can give more or less power in certain RPM ranges.
This could also be why you feel the power difference only at higher RPMs, the velocity in exhaust system lowers the pressure at the valves only at higher RPMs
Last edited:
- Joined
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- Messages
- 689
- City
- Lake Almanor, Ca.
- Vehicle Year
- 1988/2000
- Total Lift
- 9" on the 2000, 6" on the '88
- Tire Size
- 265/75/16, 31x10.50x15
- My credo
- The memories of a man in his old age are the deeds of a man in his prime
I have 2 1st gens a single cab 2.9 3.73 gears and 30's. It is a dog on hills and gets about 18 mpg.
My Super has 4:10's and 31's. It blazes up hills and gets upwards of 20 mpg if I'm doing highway driving.
The 30's look great but kill the power and mileage with 3:73 gears.
These trucks aren't speed demons the way they are built. You can donsome stuff to make them a bit more economic.
Of course the canned response is:
Drop in a 4.0 . . .
I didn't, I live with what my trucks do, but I'm old . . .
Rich
My Super has 4:10's and 31's. It blazes up hills and gets upwards of 20 mpg if I'm doing highway driving.
The 30's look great but kill the power and mileage with 3:73 gears.
These trucks aren't speed demons the way they are built. You can donsome stuff to make them a bit more economic.
Of course the canned response is:
Drop in a 4.0 . . .
I didn't, I live with what my trucks do, but I'm old . . .
Rich
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