Bad mpg. Idk why.
Thread Starter
TECH Fanatic
Joined: Mar 2011
Posts: 1,050
Likes: 2
From: Odessa, TX
Bad mpg. Idk why. I have a 01 z with a 98 ls1 in it. With the 806 heads and the egr manifold. I had a tune up when I bought the car. Plugs wires oils.
I put lts on and have 1 high flow cat after the merge on the ypipe. I don't have the rear o2s hooked up since theres no bungs. The only codes I have are
p0140, p0160 (rear o2s)
p 0412, p0418 (!AIR)
And p1336 (crank pos. relearn)
It has not been tuned. Why am I getting 150 miles to a tank?? I drive conservatively to see how long a tank will last. I KNOW something is wrong. But no idea what. Any idea?
I put lts on and have 1 high flow cat after the merge on the ypipe. I don't have the rear o2s hooked up since theres no bungs. The only codes I have are
p0140, p0160 (rear o2s)
p 0412, p0418 (!AIR)
And p1336 (crank pos. relearn)
It has not been tuned. Why am I getting 150 miles to a tank?? I drive conservatively to see how long a tank will last. I KNOW something is wrong. But no idea what. Any idea?
Thread Starter
TECH Fanatic
Joined: Mar 2011
Posts: 1,050
Likes: 2
From: Odessa, TX
I'm ordering a frost tune right now. Would the tune greatly improve my mpg?
And I'm ordering a new PCM and the tune so there's no downtime since the z is my dd. which PCM do I get? The 411 right??
And I'm ordering a new PCM and the tune so there's no downtime since the z is my dd. which PCM do I get? The 411 right??
Thread Starter
TECH Fanatic
Joined: Mar 2011
Posts: 1,050
Likes: 2
From: Odessa, TX
Not to long. The cat was ok when I put the mangaflow cat back on about a month ago.
Maf is cleaned(2 weeks ago)
How do I clean the iac?
And a ground as in one of the body grounds?
The o2s are maybe 2 months old. What are the chances they went bad that fast?
Maf is cleaned(2 weeks ago)
How do I clean the iac?
And a ground as in one of the body grounds?
The o2s are maybe 2 months old. What are the chances they went bad that fast?
You're most likely running real rich without having done a tune.
Good luck with the mail order tune. Sometimes they're good, sometimes they are terrible. If you can, get it on a dyno to tune it the proper way.
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i'm in the same boat as you i've tried everything and still get bad gas mileage my car had a tune on it when i bought it a couple months ago so im thinking that has to be the problem my cam should be in and installed in a couple weeks im hoping the dyno tune will get me some better mileage.
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^huh? the actual gas gauge isn't the best to go off of. And OP, is the city or freeway driving? If it's city, go fill up your tank, get out on the highway and just cruise 65-70mph for at least half a tank and fill back up. Do the whole miles driven divided by gas used. That's a much better way of checking your mpg.
Thread Starter
TECH Fanatic
Joined: Mar 2011
Posts: 1,050
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From: Odessa, TX
It's all city.
I was just saying the first 1/4 on the gauge lasts 37 miles the next 1/4 lasts Til 100 miles etc. I know it's not accurate but it gets on my nerves since gas is going up.
I was just saying the first 1/4 on the gauge lasts 37 miles the next 1/4 lasts Til 100 miles etc. I know it's not accurate but it gets on my nerves since gas is going up.
Let it run down to E, on E. The fill it up until the pump stops by itself the first time. You should be able to get about 14-14.5 gallons in there.
And as mentioned....you have two new front 02's......have them checked on a scanner to see if they are switching properly. Lost of people complain about bad gas mileage, and lots of times it bad/failing front 02 sensors.
And NO.....you will not always get a code until they are bad where you can notice it. But it will make you run rich enough to totally kill your gas mileage. I installed a new 02 sensor a couple months ago, it was a dud, it happens. Only takes one bad one to kill your gas mileage.
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NOPE.
Only way to know if the tune they send you is good, is too get on a dyno and check it out. Or you can drive the car on the streets if someone you know has the wide-band set-up that can hook up to your exhaust to check it out. Just feeling good won't tell you if you're running dangerously lean, rich is easy to tell, you'll smell gas and have bad gas mileage.
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just finished ordering my frost tune. hope it helps alot. 
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Thread Starter
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Joined: Mar 2011
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From: Odessa, TX
i know for sure im running rich. i smell gas all the damn time.
what about the engine itself it is a 98 with the bigger cam and the ls1 egr intake instead of the ls6 and smaller cam. since theres not egr on the engine could that be involved? i read the egr on the 98/00s kept emissions down.
what about the engine itself it is a 98 with the bigger cam and the ls1 egr intake instead of the ls6 and smaller cam. since theres not egr on the engine could that be involved? i read the egr on the 98/00s kept emissions down.
Last edited by 14k; Mar 6, 2012 at 12:34 AM.
i know for sure im running rich. i smell gas all the damn time.
what about the engine itself it is a 98 with the bigger cam and the ls1 egr intake instead of the ls6 and smaller cam. since theres not egr on the engine could that be involved? i read the egr on the 98/00s kept emissions down.
what about the engine itself it is a 98 with the bigger cam and the ls1 egr intake instead of the ls6 and smaller cam. since theres not egr on the engine could that be involved? i read the egr on the 98/00s kept emissions down.
OH well, see if the new PCM/tune fixes it. But I would want to know if the tune is right and not running too lean, which could kill the engine pretty fast. Only way to make sure, as I said above....wide band 02 readings.
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Have a freind rev the engine in PARK......put your hand right up against the exhaust, see if raw fuel spits out. If so, you're tune is just way way rich. I had a rich problem once, raw fuel would shoot out my exhaust like 6 feet and on to the ground, it was ridiculous.
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what else could i check it with? or is that all Thread Starter
TECH Fanatic
Joined: Mar 2011
Posts: 1,050
Likes: 2
From: Odessa, TX
wow... im praying that i get one of those "spot on" tunes everyone on here has.