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Discussion Starter #1
So recently I've been getting really bad gas mileage in my '97 crown vic and
it didn't have that issue before I took out the spark plugs, And put brand
new ones(Motorcraft SP-432 AGSF32FM). I did make sure they're gapped
properly to .54mm. I also replaced the fuel filter, air filter, cleaned out the
mass air flow sensor. Put when i took off the spark plugs the wires were
stuck on there because they were never took off so i used my hands and
struggled but managed to get em off but ever since i put the new spark
plugs in an put the boots back on it hasn't gotten as good gas mileage
since. I did check to see if the spark plug wires are arching and their not
visibly arching. No cuts or tears when visible inspection. The engine has
over 270K Miles put onto it. Any Suggestions? I've took a scan tool to it as
well and here's the results. Oxygen Sensor Read at: 0.5.85V at idle, Air flow
rate MAF sensor: 7.01g/s, Short term fuel Trim (B1-S2): 99.2%, Short Term
Fuel Trim (B2-S1): -1.6%, long term trim is 0.0%.
 

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When were the plug wires last replaced? Have you experienced a loss of power? What do the plugs look like (I know they were just replaced, worth a look when things aren't playing). You said you cleaned the MAF, what did you use, they can be picky. If the MAF sends a false signal, it can throw off the fuel trim.
 

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Discussion Starter #3
When were the plug wires last replaced? Have you experienced a loss of power? What do the plugs look like (I know they were just replaced, worth a look when things aren't playing). You said you cleaned the MAF, what did you use, they can be picky. If the MAF sends a false signal, it can throw off the fuel trim.
Wires have never been replaced (they're original), I only replaced the spark plugs not the wires. I have gradually had really bad power loss. I used CNC maf sensor cleaner.
 

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Plug wires build up a resistance with age, try replacing them. Years ago, I used to buy the NAPA bottom of the barrel, you cut to length plug wires... after 3 go 'rounds, I finally replaced them with a decent set. They don't need to be anything fancy, the stock ones will run you about 60 bucks. Stick with Motorcast or AC/Delco. By removing the plug wires, you may have stretched them which could exacerbate the problem.
 

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Discussion Starter #5
Plug wires build up a resistance with age, try replacing them. Years ago, I used to buy the NAPA bottom of the barrel, you cut to length plug wires... after 3 go 'rounds, I finally replaced them with a decent set. They don't need to be anything fancy, the stock ones will run you about 60 bucks. Stick with Motorcast or AC/Delco. By removing the plug wires, you may have stretched them which could exacerbate the problem.
ACdelco are $85 where i live. they have multiple brands, motorcraft, accel, standard ($74), OmniSpark($55). Which one is the best bang for my buck? or best quality i should say.
 

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What are the ones in the car? They seemed to last a while. Unless you're going high performance with hotter sparks, I'd stick with Motorcraft (Ford's brand), or AC/Delco.
 

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Discussion Starter #7
What are the ones in the car? They seemed to last a while. Unless you're going high performance with hotter sparks, I'd stick with Motorcraft (Ford's brand), or AC/Delco.
Motorcraft , but here they cost $104, is AcDelco okay ?
 

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Yup, they make a reliable product.
 

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2000 grand marquis ls with handling package, magnaflow mufflers,dual exhaust, 3.55 rear axle
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Just changed all 8 today and still not better gas mileage . And yes I did make sure to install them correctly . Any other ideas?
What were your precise mpg numbers before and after? What method did you use to check your mpg?
 

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Discussion Starter #11
What were your precise mpg numbers before and after? What method did you use to check your mpg?
I just use the mpg counter on my dashboard but it went from 12.5mpg to 8.9mpg now with the new spark plugs.
 

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Apart from the MPG is the car running o.k ? Are the spark plugs you fitted the correct ones as it seems that was a change year for the Crown Vic , Might apply , might not .


Overview
1992 Ford Crown Victoria LX
ProductionJanuary 14, 1991 – October 1997

Later models ,

Motorcraft® Spark Plugs

1998 3.4L (N) Taurus SHO ............. AGSF32FMF4 432* .044 4.6L (W)

Crown Victoria (Gas) AGSF32PMF4 493* .054 4.6L (9)

 

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Discussion Starter #13
Apart from the MPG is the car running o.k ? Are the spark plugs you fitted the correct ones as it seems that was a change year for the Crown Vic , Might apply , might not .


Overview
1992 Ford Crown Victoria LX
ProductionJanuary 14, 1991 – October 1997

Later models ,

Motorcraft® Spark Plugs

1998 3.4L (N) Taurus SHO ............. AGSF32FMF4 432* .044 4.6L (W)

Crown Victoria (Gas) AGSF32PMF4 493* .054 4.6L (9)

The car runs good, Just has a lack of mpg ever since I changed them and I'm using those exact spark plugs for the crown vic.
 

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A thermostat sticking open / longer would cause higher MPG About all I can think of at the moment that would cause it after all the work you have already done .
 

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Discussion Starter #15
A thermostat sticking open / longer would cause higher MPG About all I can think of at the moment that would cause it after all the work you have already done .
Thank u very much ill try that and tell the results.
 

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Discussion Starter #16
A thermostat sticking open / longer would cause higher MPG About all I can think of at the moment that would cause it after all the work you have already done .
It took a while for the engine to warm up (11 mins or longer) and i checked to see if the fluid in the radiator is swirling and nothing . Even when i let it sit for 5 mins with the heater on.
 

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2000 grand marquis ls with handling package, magnaflow mufflers,dual exhaust, 3.55 rear axle
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It took a while for the engine to warm up (11 mins or longer) and i checked to see if the fluid in the radiator is swirling and nothing . Even when i let it sit for 5 mins with the heater on.
Those mpg numbers are really bad even before you changed the plugs. Is there any chance it is leaking fuel? When you changed the fuel filter, did the fuel lines look rusty? Did the gas tank look wet?
 

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Discussion Starter #18
Those mpg numbers are really bad even before you changed the plugs. Is there any chance it is leaking fuel? When you changed the fuel filter, did the fuel lines look rusty? Did the gas tank look wet?
No, I checked the lines and they weren't brittle or rusting.
 

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Another thing to check is the egr passage from the exhaust manifold to the intake plenum. They’re known to clog and can cause lowered gas mileage and pinging.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #20
Another thing to check is the egr passage from the exhaust manifold to the intake plenum. They’re known to clog and can cause lowered gas mileage and pinging.


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Do egr valves have gaskets on them? and would i have to replace it or can i just clean it with throttle body cleaner and call it?
 
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