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Old 03-05-2019, 07:41 PM   #1
xactorocker
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Exclamation Fuel Economy

Hey I'm getting around 11 miles per gallon, which from my knowledge is not great. So what I have done is change plugs wires and the o2 sensor. Also my ac does not work if that's any help. Idk if clutch is stuck if that could cause it. One more think I also dont drive more can 3 miles at a time just to work and back engine does not heat all the way up. Any help is appreciated thank you. And the car is a 85 245 with the m46 trans.
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Old 03-05-2019, 07:55 PM   #2
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Spark plugs look good? tires inflated correctly and correct size? Car idle and run good? Still have catalytic converters? Was mileage higher last Summer? more info helps
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Old 03-05-2019, 09:19 PM   #3
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Considering that it is Winter in Atlanta, even though it has been a mild one, and you only drive 3 miles per trip I would suggest that 11mpg is about what you should expect.

The tire pressure suggestion is a valid one. If you last tested the pressure last Summer they are probably reading 24psi now.

Do the spark plugs and that may add 1-2 mpg at best.

Take it on a road trip to the Georgia mountains, check the mpg and report back.
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Old 03-05-2019, 09:36 PM   #4
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Thank you all for the help going to go check all these things out tomorrow. And I actually put in new spark plugs last week. And good idea for the mountains, I will go camping soon up there.
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Old 03-05-2019, 11:22 PM   #5
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Are you sure your speedo/odo is correct? Is your 3 miles heavy stop and go?
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Old 03-06-2019, 02:29 AM   #6
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Even in fairly heavy (not yet Atlanta bad, but the infrastructure here is reaching bay-area/atlanta levels, soon to be Hell.A-Scape), an EFI 240, unless it's like -40 out, should get about 18ish city with typical driving habits.

So many variables for economy, but that's definitely below what the window sticker would suggest . 20ish city traffic mix-27highway is a healthy/average N/A EFI 240 in a moderate climate.

Even if it's pretty cold out, no block heat, it should get warm within 2 miles, 240s heat up fast with the heater valve closed if the T-stat is any good, even non-turbo models without a watercooled turbo to exchange lots of BTUs right next to the hot exhaust into the cooling circuit.

My extensive 3 seconds of googling suggest that March in atlanta should be 43-66ish degrees out/mild/moderate?

Even navigating stressful San Francisco hills/horrible traffic on terrible california gas with stuff on the roof, the beater '87 245 would get ~18-19ish. Coolant Warm-up should take 5?ish minutes of driving or ~1 mile cruising at 60mph steady in the flat with the heater valve closed on a 45(ish)? degree day?
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Old 03-06-2019, 08:17 AM   #7
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I'm with you KJets - hell, MINE gets 19/26 if you keep your foot out of it. Just trying to confirm he's got a number that was calculated properly. ODO's off and then we find out fuel use is estimated by looking at the fuel gauge...

Last edited by M.H. Yount; 03-06-2019 at 08:23 AM..
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Old 03-06-2019, 05:34 PM   #8
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I'm getting 20 pure city, 28 pure highway. I was getting 23 pure highway before I had my injectors ultrasonic'd and flowmatched. I'd try getting those cleaned out and see if it doesn't help. After seeing the nasty crap that was in the pintle caps, you'll want to get them cleaned.

Either that or buy some cheap injectors from the FS and swap em in...
Ohm test wires, check plug electrode condition and gap, look for distributor & rotor carbon build up, all those factors can slowly drag down your mpg.
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Old 03-06-2019, 08:00 PM   #9
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Kjets so it is very heavily stop and go. So maybe that's part of it. You said EFI but would this be different if it is MFI that's what my 85 is as far as I know thank you.
Then I'm pretty sure its accurate but will give it a check
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Old 03-06-2019, 08:15 PM   #10
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Rats nest in air filter?
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Old 03-06-2019, 08:23 PM   #11
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Rats nest in air filter?
na new filter but one clip on it is snapped.
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Old 03-07-2019, 03:25 PM   #12
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Ha. I saw a car coming out of storage with an air box filled with dog food once. Bad mouse!
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Old 03-07-2019, 03:34 PM   #13
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Quote:
Originally Posted by xactorocker View Post
Kjets so it is very heavily stop and go. So maybe that's part of it. You said EFI but would this be different if it is MFI that's what my 85 is as far as I know thank you.
Then I'm pretty sure its accurate but will give it a check
In 1985 240 turbo has MFI. N/a has EFI.
My 93 wagon with just around town driving gets about 20mpg.
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Old 03-07-2019, 04:58 PM   #14
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Ok well thank you. Is there any way that the catalytic converter is bad and that's why I'm getting bad milage? Dont know how old it is. Thank you
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Old 03-07-2019, 05:22 PM   #15
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Quote:
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Ok well thank you. Is there any way that the catalytic converter is bad and that's why I'm getting bad milage? Dont know how old it is. Thank you
If it's plugged/melted, it adds parasitic pumping loss as your engine has to force the exhaust out of a restrictive environment.

If the cat honeycombs are broken or shattered, it won't affect mpg, just emissions.

your cat should be bolt on, take it off, shine a flashlight in there and take a peek.

I'd definitely suspect injection system first though. Think about how long it's been since those injectors have been cleaned (if ever). Your O2 sensor might sense that you're running at stoich when in reality, a cylinder might be running rich, and another might be lean, etc. you want all your cylinders to have equal air and fuel input so that when your o2 sensor adjusts the mixture, it does so effectively for all cylinders.
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Old 03-07-2019, 06:36 PM   #16
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If you do have a 240 turbo. The cat is very close to the engine and it's very common for those to clogup when they get old. My turbo had a clogged cat back when I bought it in 1995. Over the years though, I've experienced both types of converters failing in various ways clogging the exhaust flow.
On a 240 turbo there is a test port on the top of the downpipe. You can install a pressure gauge in the port. If I recall correctly there should be very little pressure generated. Something like 1.5psi. Any more than that it's affecting the exhaust flow.
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Old 03-07-2019, 10:02 PM   #17
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Quote:
Originally Posted by IansPlatinum View Post
I'm getting 20 pure city, 28 pure highway. I was getting 23 pure highway before I had my injectors ultrasonic'd and flowmatched. I'd try getting those cleaned out and see if it doesn't help. After seeing the nasty crap that was in the pintle caps, you'll want to get them cleaned.

Either that or buy some cheap injectors from the FS and swap em in...
Ohm test wires, check plug electrode condition and gap, look for distributor & rotor carbon build up, all those factors can slowly drag down your mpg.
about the same numbers i was getting with my 88. solid 28 mpg on the hwy
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Old 03-08-2019, 04:02 AM   #18
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My 240 Turbo w. B19ET + M46 was heavy drinker, around 20 MPG, next car was 245 with B200F + M47 and it used something 28-29 MPG. Daily commuting stayed the same.

I was like "whathahek" when consuming first full tank. I was used to get max. 300 miles with full tank, and with 245 odemeter kept running on. Full tank lasted almost 450 miles.
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Old 03-08-2019, 12:30 PM   #19
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I get a bit better mileage with a chipped ezk. I run premium fuel so it was nice to put that in and get a few more miles per tank.
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Old 03-08-2019, 12:34 PM   #20
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These numbers just seem crazy I just don't understand what problem could be causing me to lose half the fuel economy. I am really hoping it's because of the stop and go the whole way everywhere we will see.
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Old 03-08-2019, 03:23 PM   #21
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Quote:
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I get a bit better mileage with a chipped ezk. I run premium fuel so it was nice to put that in and get a few more miles per tank.
I could believe that. On Dyno around 2000 rpm on low load (cruise) effiency of B230 was remarkable better with 40 Deg timing. No way to get through smog test with that timing. HC was over 200 ppm, but everything was fine 15 with Deg, but torque was lower.
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Old 03-08-2019, 03:28 PM   #22
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That's cool you were able to adjust the timing. Adding the chip was a really nice change. The engine even has a different exhaust note which sounds like it is happier. Seemed to help at all rpms. I don't rev it over 5k now since it is a 420k miles engine.
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Old 03-08-2019, 05:47 PM   #23
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Quote:
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These numbers just seem crazy I just don't understand what problem could be causing me to lose half the fuel economy. I am really hoping it's because of the stop and go the whole way everywhere we will see.
Bud. Fill er up, take her for a drive to a nice restaurant an hour's highway cruise away, eat, come back, fill er up again, do some math. Map the trip to eliminate ODO from equation. Scientific process. Pemdas.
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Old 03-11-2019, 01:55 PM   #24
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Originally Posted by IansPlatinum View Post
I'm getting 20 pure city, 28 pure highway. I was getting 23 pure highway before I had my injectors ultrasonic'd and flowmatched. I'd try getting those cleaned out and see if it doesn't help. After seeing the nasty crap that was in the pintle caps, you'll want to get them cleaned.

Either that or buy some cheap injectors from the FS and swap em in...
Ohm test wires, check plug electrode condition and gap, look for distributor & rotor carbon build up, all those factors can slowly drag down your mpg.
That dramatic of a change in MPG just from cleaning the injectors??
My NA 240 has never cracked 23mpg even if I'm just going 70-75mph on the freeway
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Old 03-11-2019, 02:42 PM   #25
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Hey I'm getting around 11 miles per gallon,
And the car is a 85 245 with the m46 trans.
Pull the vacuum hose off the fuel pressure regulator (at front of fuel rail) and see if any gas leaks out. If so, the internal diaphragm has split and is leaking raw fuel into the intake. The lack of "suck" against the diaphragm also closes the internal valve, simulating full throttle, and raising the pressure at the injectors.
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