Mpg?

[SVOFANATIC]

Well still no codes. Anyone have any ideas? 19mpg last fill up with 270 of the 290 I went being hwy.

Also let me add a few things. Every once and awhile when I start the car it will idle at 500-600 fluctuating almost like the car is cammed. If I tap the gas once it idles normally at 900rmps or so. I know the idle won't cause the bad gas mileage but wondering if something else that is causing the idle could also mess up my mpg?

Also I ran some seafoam through the intake I found out afterwards that it isn't good for this engine to run it through the Intake could I have messed something up?

 

[220ksho]

Did you change out your thermostat yet?

 

[SVOFANATIC]

Yes I did.

 

[SHOtime2511]

check for vac leaks.

 

[SVOFANATIC]

I'm not seeing any kind of vac leaks. I just checked by hand. plugged lines see if it did anything and nope. So if it is a vac leak it has to be in the gasket area.

 

[frosho]

Try the starter fluid method. Spray it around the intake gaskets, couplers, and vac lines, and listen for the idle to rise.

 

[SVOFANATIC]

Nothing just used a full can on all the couplers, gaskets, vac lines ect. and no bubbling or raise in idle. Could it be spark plug gap? I never did gap mine.

 

[SVOFANATIC]

Ok so if I'm getting pretty much the same gas mileage when I do almost all hwy driving compared to when I run down the strip all day what does that mean? Is the car running rich?

 

[220ksho]

So, now that you changed the thermostat... what is your time to warm up? You mentioned before that it was 5 miles or so. This is way too long especially if you get on the highway right away and "get on it".

On the strip, your engine gets nice and hot and the fuel mixture becomes normal. If you run 70mph down the highway at below normal temp even for half of your trip, it would explain the poor mpg.

How hot does it get on the highway. (max) i.e. what letter does the needle point to.

 

[SVOFANATIC]

around the M I would say. Warm up time (I.E heater kicks on in the cold) by the time I get out of my driveway (long driveway) 150-200 yards

 

[SHOtime2511]

What plugs do you use?

 

[SVOFANATIC]

Not motorcrafts.

Denso double platinum's

 

[SVOFANATIC]

Should I get motorcraft plugs?

 

[SHOtime2511]

pull a few out and see how they burn.

 

[SVOFANATIC]

Tan to orangish color so the mixture is right WTF? And I pulled all 6. I think I'm going to drop the money on motorcraft plugs and wires as the wires look good but I've never replaced them and the plugs well motorcrafts better.

 

[SVOFANATIC]

Well I didn't get plugs and wires but I just had a thought. What would cause me to have bad mpg but still have the right AFR? Fuel leak? When I did the engine swap I didn't change the washers at the fuel rail maybe one of those is leaking I will check here in the next day or so. Hard to check now as of all the rain.

 

[SHOtime2511]

are you sure you are calculating fuel mileage correctly?

 

[SVOFANATIC]

positive. 290 miles 15 gallons 19 mpg.

 

[Bob Gervais]

When you scanned codes, did you do a KOER, or KOEO?

Also, what computer does this car have in it?

 

[Lorenr]

Poor MPG

Plugged catalytic converters and worn out oxygen sensors will give you poor fuel economy. Sounds as though you checked everything else.

The new y-pipes solve this.

:swing: