Crank angle sensor cause of bad gas mileage?

arabeclipse · Jun 16, 2013

I was informed by a man today that my current 1995 GST has something wrong with it because of it having 23mpg...that's one the best I've ever seen out of ANY boosted DSM so far! The only reason he told me that something is wrong with my car is because he "has had many Eclipses and managed to get them all to have 29mpg highway." Ok man, I haven't even met a 420a guy with that kind of mileage. He suggested changing my crank angle sensor and that should get my gas mileage up to par.

What do you guys think? (mods are on my profile to determine my mileage)

99ECLIPSEGSXDSM · Jun 16, 2013

My 420a got 30 when I wasn't beating on it. How heavy is your foot? Best I've gotten was 27.9 but I was always out of boost. Wasn't very fun

DSM1G90 · Jun 16, 2013

About right for combination city/highway driving for a 3000LB vehicle being pulled around by a 4cylinder motor.

Lose 600 lbs, stay out of boost, or disable the turbo and then your mileage might go up.

I'm lucky to get 22 in city driving, but can hit 29 on the freeway at 80mph with the cruise on.

arabeclipse · Jun 17, 2013

99ECLIPSEGSXDSM said:
My 420a got 30 when I wasn't beating on it. How heavy is your foot? Best I've gotten was 27.9 but I was always out of boost. Wasn't very fun

I really don't drive the car that hard. I'm not in boost unless I'm passing. I'm that 2,500rpm shifter.

iceman510 · Jun 17, 2013

First off, your crank sensor is merely an input, and if functioning properly will not detract from your fuel mileage. I don't see his point.

mikgsxx · Jun 17, 2013

DSM1G90 said:
About right for combination city/highway driving for a 3000LB vehicle being pulled around by a 4cylinder motor.

Lose 600 lbs, stay out of boost, or disable the turbo and then your mileage might go up.

I'm lucky to get 22 in city driving, but can hit 29 on the freeway at 80mph with the cruise on.

My dsm got right at 22-24 city 27-30 hwy. And that was hard to do LOL

tater · Jun 17, 2013

To get better mileage make sure you stay up to date on your maintenance, make sure your tire are inflated to the right air presser and change your plugs. It also helps to keep your air filter clean.

handsome_black · Jun 17, 2013

iceman510 said:
First off, your crank sensor is merely an input, and if functioning properly will not detract from your fuel mileage. I don't see his point.

This. I don't see where a working crank sensor can or would cause a mpg problem. He sounds shady to me, mechanic? Not so sure about that. You don't diagnose a car based loosely on what you think or have heard other peoples cars have done or didn't do.

Make sure all your routine maintaince is correct and see how the car performs then.

WES_393 · Jun 17, 2013

If the CPS was faulty and giving an intermittent signal then it could cause misfires, which can cause the front O2 sensor to read lean. But you would definitely notice the amount of misfiring it would take to have a serious impact on gas mileage.

The biggest factor in gas mileage is your right foot. Remember that turbocharged engines need a richer fuel mixture during boost. It also doesn't help that our factory tune is very liberal with fuel delivery. So the more you spool the turbo, the more fuel your going to burn.

DSM1G90 · Jun 17, 2013

So the more you spool the turbo, the more fuel your going to burn.

And this can go for NT vehicles.
You open that throttle plate of both carbureted and injected vehicles, that sudden demand for fuel will always be there.

So, remove the lead from the right foot to get better mileage and to keep you living longer.

wolfmanderek · Jun 17, 2013

I get 30mpg with my talon tsi fwd but that's by not hitting boost at all and keeping the rpms down low.

arabeclipse · Jun 18, 2013

WES_393 said:
If the CPS was faulty and giving an intermittent signal then it could cause misfires, which can cause the front O2 sensor to read lean. But you would definitely notice the amount of misfiring it would take to have a serious impact on gas mileage.

The biggest factor in gas mileage is your right foot. Remember that turbocharged engines need a richer fuel mixture during boost. It also doesn't help that our factory tune is very liberal with fuel delivery. So the more you spool the turbo, the more fuel your going to burn.

No misfires/CEL light saying so. Maintenance is up to date also. That's great info though. Like I said though, I drive pretty carefully but I'm going to take it even further to see how much more gas I can save.

handsome_black said:
This. I don't see where a working crank sensor can or would cause a mpg problem. He sounds shady to me, mechanic? Not so sure about that. You don't diagnose a car based loosely on what you think or have heard other peoples cars have done or didn't do.

Make sure all your routine maintaince is correct and see how the car performs then.

I didn't diagnose with my car with anything because I never thought there was anything wrong with it. That's why I came to the forum. And no, he was just a random guy who claims he's had many DSMs already.

mikgsxx said:
My dsm got right at 22-24 city 27-30 hwy. And that was hard to do

How did you do it?

Firsts tuner · Jun 19, 2013

Bcause we all should listen to the hobo at the gas station parking lot. LOL

.Weall got better gas mileage before they started putting 10 and 15% ethanol in regular pump gas.

Black-Out · Jun 19, 2013

^^^ So true ^^^

MichaelSuch · Jun 19, 2013

My '92 GS-T got a very consistent 29-30mpg staying out of boost and driving 60-65. My driving is literally almost all highway though. That was with a built 2.3L, stock turbo (also with a borg 62mm mileage didn't change), and tuned on Link by me. My '92 AWD was lucky to get 23-24mpg driving the same way. Knock sensor was on its way out and was pulling timing all the time. My '95 TSi AWD Auto with a built 2.3L same as the GST, made 24-25mpg on a stock sized turbo, no FMIC. I contribute the lower MPGs due to the 4spd auto. Changing your CAS won't help. Is your MAF after the greddy BOV? If it's venting to atmosphere after the MAF then you're losing MPGs there for sure.

arabeclipse · Jun 23, 2013

MichaelSuch said:
My '92 GS-T got a very consistent 29-30mpg staying out of boost and driving 60-65. My driving is literally almost all highway though. That was with a built 2.3L, stock turbo (also with a borg 62mm mileage didn't change), and tuned on Link by me. My '92 AWD was lucky to get 23-24mpg driving the same way. Knock sensor was on its way out and was pulling timing all the time. My '95 TSi AWD Auto with a built 2.3L same as the GST, made 24-25mpg on a stock sized turbo, no FMIC. I contribute the lower MPGs due to the 4spd auto. Changing your CAS won't help. Is your MAF after the greddy BOV? If it's venting to atmosphere after the MAF then you're losing MPGs there for sure.

I have the maf before the bov and tuned properly. That entire set up actually got my mpg's way up from stock when I first bought the car.

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Crank angle sensor cause of bad gas mileage?

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