2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Terrible gas mileage, running rich?

Old Dec 13, 2007 | 04:34 PM
  #26  
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http://mazdatrix.com/getprice.asp?partnum=18-8400-8574
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Old Dec 13, 2007 | 04:43 PM
  #27  
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thanks. i kept looking on the site for engine coolant temp sensor and couldnt see it anywhere.

i just ordered it. should be here by monday. thanks again
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Old Dec 13, 2007 | 06:57 PM
  #28  
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Originally Posted by SailentShadow
I get just about 10mp/g

stock everything besides exhaust and a cone-filter.... oh, and a Walbro.
BINGO.

I replaced my stock pump with a Walbro a couple years ago and instantly got shitty mileage and less power in the bottom end. I went back to the stocker and all is good.

Regardless of what you do to improve your mileage, whether it be a ECT sensor or whatever, you should get a stock pump and put it in with a new sock filter. A walbro is enough pump for a modded TII but way too rich for an NA.

Pingpong, do you have a Walbro in your car or stocker?

Last edited by scrip7; Dec 13, 2007 at 07:02 PM.
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Old Dec 14, 2007 | 03:14 AM
  #29  
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Originally Posted by scrip7
BINGO.

I replaced my stock pump with a Walbro a couple years ago and instantly got shitty mileage and less power in the bottom end. I went back to the stocker and all is good.

Regardless of what you do to improve your mileage, whether it be a ECT sensor or whatever, you should get a stock pump and put it in with a new sock filter. A walbro is enough pump for a modded TII but way too rich for an NA.

Pingpong, do you have a Walbro in your car or stocker?
Nope, the pump should be stock from what I can tell. I'll probably have to save up for a SAFC sometime soon. Seems like my highway mileage took a hit to; average dropped to around 20MPG on the highway. Hopefully this hasn't killed my cats yet; I just got new ones put on to pass smog recently, but I'm getting pretty sizeable backfires shifting at redline sometimes.

All this just makes me realize how much easier and cheaper it was to work on my bike. All I had to do on that was adjust the air/fuel mixture screw to lean it out......
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Old Dec 14, 2007 | 03:28 AM
  #30  
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buy a honda. MUAHAHAHA
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Old Dec 14, 2007 | 03:42 AM
  #31  
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Originally Posted by Ex-Eg-Driver
buy a honda. MUAHAHAHA
Ironically, I was debating between getting either the RX7 or upgrading my bike to a Honda CBR600 F4i. Sometimes (read: every time I'm stuck in traffic or looking for a parking spot around campus or filling up on gas), I still wish I had gotten the bike.
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Old Dec 14, 2007 | 08:21 AM
  #32  
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my god people. my TII with a highflow fuel pump and full exhaust gets 20mpg average. and thats with me driving the hell out of it 50% of the time.
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Old Dec 14, 2007 | 09:01 AM
  #33  
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Originally Posted by xUnKnOwNx
i called the guy from my shop and asked about the ECT. he said theres 2. one for the gauge and one for the ECU? should we replace both?

Has the ECT been tested, or are you just going to replace it?

Also, while you are there have the mechanic replace the harness connector as well. 99% chance that the old one is about to fall off.
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Old Dec 14, 2007 | 10:09 AM
  #34  
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sometimes I get up to 350 to a tank and about 20-22 mpg so I'm pretty happy about that
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Old Dec 14, 2007 | 05:11 PM
  #35  
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Originally Posted by Aaron Cake
Has the ECT been tested, or are you just going to replace it?

Also, while you are there have the mechanic replace the harness connector as well. 99% chance that the old one is about to fall off.
im just gonna replace it. i think the previous owner drove the **** out of the car and didnt do any maintenance. i think this might also be related to my temperature gauge, usually on most cars the temp gauge is about half way on normal operating temperatures. well mine barley reads about 1/4.
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Old Dec 15, 2007 | 10:39 AM
  #36  
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Originally Posted by xUnKnOwNx
im just gonna replace it. i think the previous owner drove the **** out of the car and didnt do any maintenance. i think this might also be related to my temperature gauge, usually on most cars the temp gauge is about half way on normal operating temperatures. well mine barley reads about 1/4.
Do you have an S4 or S5? The S4 should normally read 1/4th, wheras the S5 should be at 1/2.
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Old Dec 15, 2007 | 10:40 AM
  #37  
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The ECT is for the ECU only and does not relate to the temperature gauge in any way.

Your gauge is supposed to read 1/4 at normal operating temperature.
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Old Dec 15, 2007 | 03:47 PM
  #38  
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Do not replace the the coolant temp sensor without testing it first. IMO is unlikely this is the problem, so it could be a waste of money.

As Aaron said above, if the ECU thinks the engine is cold it will increase fuelling. But IMO it's very unlikely the sensor could fail in this manner. It's just a simple thermistor, so it can't fail in one "position", it either works or it doesn't. If it fails, the ECU ignores it and assumes the engine is warm (176degF). This makes the engine run poorly when cold, but it'll run normally when it warms up. This would actually decrease average fuel consumption slightly.

Always test sensors before replacing them. In this case a simply voltage reading at the ECU will prove whether the coolant temp sensor is okay.
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Old Dec 15, 2007 | 04:01 PM
  #39  
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so yeah, my motor runs like crap when i start it up and its smells terrible, a real gasy smell, but when it warms up it runs like a champ and the gas smell goes away. when its warmed up it runs great and the gas smell goes away
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Old Dec 15, 2007 | 08:45 PM
  #40  
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My car's mileage seems to have gone down the crapper as of late.

I seem to get about half the mileage as usual.

I'm sure part of it has to do with jackrabbit driving style and lack of cruise control... but it smells like it's running way richer than usual.

It seemed to start from about the time my air conditioning hoses came undone... but I doubt that's related.

I don't think it's timing or TPS, since I set them...a lot. And my coolant temp and O2 sensor are about a year old.

I personally think either my ECU is retarded (which might also explain the ridiculously inconsistent idle), or I have a weak rear leading ignition coil (either that or it's timing is off, compared to the front rotor, which is probably an ECU issue).
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Old Dec 15, 2007 | 09:59 PM
  #41  
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u cant tell me that this is normal operating temperature....



right now my gas is just slightly under half and i drove for 45 miles, mostly city. running on premium gas. what can be wrong?
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Old Dec 16, 2007 | 10:18 AM
  #42  
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That's quite low.

Has some idiot removed the thermostat from you car? If it has been removed, the car may never warm up and you might be in cold start constantly. If the thermostat is aftermarket, replace it with a Mazda unit.
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Old Dec 16, 2007 | 05:51 PM
  #43  
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Originally Posted by Aaron Cake
That's quite low.

Has some idiot removed the thermostat from you car? If it has been removed, the car may never warm up and you might be in cold start constantly. If the thermostat is aftermarket, replace it with a Mazda unit.
that cant be the case if my car floods and have hot start issues right?
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Old Dec 16, 2007 | 06:30 PM
  #44  
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Originally Posted by flamin-roids
The engine coolant temp sensor can ruin your gas mileage? You learn something new everyday. BTW my '90 GTU got amazing gas mileage and it had a fuel leak. I drove from salt lake city to denver (550 miles) on a single tank.
i find that extremely hard to believe.....
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Old Dec 17, 2007 | 09:10 AM
  #45  
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Originally Posted by xUnKnOwNx
that cant be the case if my car floods and have hot start issues right?
I'm not sure I understand the question. For the $20, I'd almost replace the thermostat with one from the dealer by default...
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Old Dec 17, 2007 | 04:14 PM
  #46  
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try your o2 sensor they can make your car run rich
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Old Dec 17, 2007 | 05:47 PM
  #47  
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try not to boost. most ppl blame poor fuel economy on their car, when in most cases its the way they drive. this is especially true on turbo cars. look at you boost gauge(glance at the gauge, keep your eyes on the road) and try to drive without going over 0(kinda hard for the small turbo but doable). sure you'll be slower in traffic but you'll also save gas. and you'll be a better driver
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Old Dec 17, 2007 | 06:27 PM
  #48  
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I thought he said it was NA...

but anyway I drive my '7 like there's a fire under my butt because I love it too much to let it live a life of boring commuting. 16mpg is good for me!
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Old Dec 17, 2007 | 06:33 PM
  #49  
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I went from ~250 miles on a full tank to about ~340 miles (mixed driving) just by finally getting around to swapping out my 150k mile drive shaft with a brand new one

Taken Saturday as I was filling up the tank: 351.4 miles
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Old Dec 17, 2007 | 06:35 PM
  #50  
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you put me to shame, haha
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