O2/Exhaust question
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Posting Guru
Joined: Jul 2004
Posts: 2,244
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From: Cottage Grove, WI
O2/Exhaust question
Hey guys, does anyone know if the OBD I Single O2 sensor setup need the heat from a cat converter to work properly, and enter closed loop?
Reason I ask is I have a good running 351 in my 95 w/ new injectors FPR O2 sensor, tune up, all sorts of other new parts, and i can only squeeze 9mpg out of it w/ a 4r70w trans... I think i should be able to get more than that. I removed the stock cats when i did my exhaust, and im wondering if i should put a hiflow one back on there...
Reason I ask is I have a good running 351 in my 95 w/ new injectors FPR O2 sensor, tune up, all sorts of other new parts, and i can only squeeze 9mpg out of it w/ a 4r70w trans... I think i should be able to get more than that. I removed the stock cats when i did my exhaust, and im wondering if i should put a hiflow one back on there...
Fleet Mechanic
Joined: Nov 2011
Posts: 1,823
Likes: 43
From: New York
How's your coolant temp looking? Might you have a thermostat that isn't fully closing, and thus keeping your engine too cold? That WILL have a measurable effect on fuel economy, especially in cold weather.
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Posting Guru
Joined: Jul 2004
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From: Cottage Grove, WI
OK, here goes.
Checked for codes a couple weeks ago, Came up clean.
I live in WI, Its been below freezing for weeks now, but Ive had this crap mileage since I did the engine swap a year and a half ago.
Once the truck warms up to operating temp, it runs right around the "O" in "Normal," whatever that equates to.
Truck was originally a MAF 302/4R70W/3:31s. 33"s and 6" lift. Upgraded to 4:10 gears and a 351W. I used the 302MAF controls/computer to run the 351W. When I did the swap, this is the list of new parts I put on the engine:
-Gaskets
-Valve Seals
-Oil Pump
-Water Pump
-Thermostat (195*)
-Engine Coolant Temp Sensor
-Radiator
-Fuel Injectors
-Fuel Pressure Regulator
-Plugs/Wires/Cap/Rotor
-Distributor
-Air Filter
-Shorty Headers
-O2 Sensor
Timing is set to 12* BTDC
Since I was already in there to do the swap, I took this time to do alot of other needed repairs, like replacing a leaky radiator.
And just cuz i do like to show off, heres a pic of the truck we're talking about
Checked for codes a couple weeks ago, Came up clean.
I live in WI, Its been below freezing for weeks now, but Ive had this crap mileage since I did the engine swap a year and a half ago.
Once the truck warms up to operating temp, it runs right around the "O" in "Normal," whatever that equates to.
Truck was originally a MAF 302/4R70W/3:31s. 33"s and 6" lift. Upgraded to 4:10 gears and a 351W. I used the 302MAF controls/computer to run the 351W. When I did the swap, this is the list of new parts I put on the engine:
-Gaskets
-Valve Seals
-Oil Pump
-Water Pump
-Thermostat (195*)
-Engine Coolant Temp Sensor
-Radiator
-Fuel Injectors
-Fuel Pressure Regulator
-Plugs/Wires/Cap/Rotor
-Distributor
-Air Filter
-Shorty Headers
-O2 Sensor
Timing is set to 12* BTDC
Since I was already in there to do the swap, I took this time to do alot of other needed repairs, like replacing a leaky radiator.
And just cuz i do like to show off, heres a pic of the truck we're talking about
Fleet Mechanic
Joined: Nov 2011
Posts: 1,823
Likes: 43
From: New York
First off, given the change in gearing and tire size from stock, have you verified your odometer's accuracy?
Second, given all the fuel-efficiency strikes against you (4x4, 351, lifted, big tires, automatic, 4.1 gearing), I don't know that you should be expecting much more than about 10MPG.
It sounds like your thermostat is closing and coolant temp is where it should be - mine registers about the same as yours.
One thing to do regardless... Pull your PCM and check the capacitors for leakage. I've yet to find one that doesn't have failing components.
Second, given all the fuel-efficiency strikes against you (4x4, 351, lifted, big tires, automatic, 4.1 gearing), I don't know that you should be expecting much more than about 10MPG.
It sounds like your thermostat is closing and coolant temp is where it should be - mine registers about the same as yours.
One thing to do regardless... Pull your PCM and check the capacitors for leakage. I've yet to find one that doesn't have failing components.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Has the speedo been recalibrated for those 33's? If not you're actually getting 12-13mpg which is normal city numbers for a 351 powered truck.
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Thread Starter
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Posting Guru
Joined: Jul 2004
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From: Cottage Grove, WI
The speedo does actually read a little slow, I reprogrammed it when i got the truck, but the numbers must have been off. Its dead nuts accurate with 35" tires, but on 33s it reads 4-5mph fast at 60. Verified with the 2 different "your speed is" signs in our town
How would I go about doing this, and fixing it if need be?
How would I go about doing this, and fixing it if need be?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
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