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Bad MPG, possible low vaccum, orange coolant?

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Old 10-11-2018, 11:05 PM
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Bad MPG, possible low vaccum, orange coolant?

I am currently getting about 13.37 MPG. My drive to work is about 10 miles freeway and 5 local. I know to not expect great numbers but I want to get closer to the average rating of 17. I am going to pull the plugs and test the coils soon.

I also got an OBD and Torque. I noticed that my vaccum/boost is possibly low. At a light it fluctuates around 11-12 and with the a/c on it drops to 9ish. I though that maybe the previous owner didn't plug up the VFAD but it is plugged so IDK. The elevation in San Jose is 82'

The car has 106,000 miles and as far as I can gather the engine was replaced around 33,000. It has an AEM cold air intake and a racing beat catback exhaust. The car starts whether cold or hot and seems to drive fine.

Another thing is the car has some kind of orange coolant. I am getting temperatures around 200 while it is just about 70ish outside now while on the freeway driving at like 65. At idle it starts to climb over 200.

Are any of the things normal or can anybody give me some additional input?
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Old 10-11-2018, 11:22 PM
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The vacuum does seem low and temperature sounds high. What kind of LTFT (fuel trim) do you see on warm idle?
For the temperature, does the car still have the plastic undertray below the radiator? You really need that.
Orange coolant as in dirty/rusty or uniform but orange? If it's suspicious, I'd flush it and replace with Mazda FL22.
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Old 10-11-2018, 11:39 PM
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Originally Posted by Loki View Post
The vacuum does seem low and temperature sounds high. What kind of LTFT (fuel trim) do you see on warm idle?
For the temperature, does the car still have the plastic undertray below the radiator? You really need that.
Orange coolant as in dirty/rusty or uniform but orange? If it's suspicious, I'd flush it and replace with Mazda FL22.
I just set up torque with the PID for the trims, so I'll get back to you on that. If you mean the tray under the front bumper then it is still there. I believe the coolant is inherently orange itself. I was trying to figure out what kind it may be.



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Old 10-12-2018, 05:27 PM
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This morning was colder than yesterday evening, the LTFR was at -16 at idle. And the vaccum was even even lower today. This screenshot was right at the end of my drive at idle.


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Old 10-12-2018, 05:39 PM
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You are running a bit rich.

Also, the MAF reading seems a little high. Usually it should sit around 4.5~5g/s at idle.

Have you cleaned the MAF yet?
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Old 10-12-2018, 05:54 PM
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Have you cleaned your MAF?
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Old 10-12-2018, 05:59 PM
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The AEM intake could have something to do with the low mpg as they don't register the same g/s as a stock intake . That LTFT will be mostly from the AEM ...IMO .
What is ltft when you are cruising at speed limit ?
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Old 10-12-2018, 08:28 PM
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So the vaccum is still around 12, that meter in the picture is in psi. I think even though it says otherwise, some kind of bug in the program. My other dial still reads around 12.

I have not cleaned the MAF sensor yet. I will tomorrow then.

When I press the gas pedal the LTFT is almost always 0. Same for cruising at any speed, even highway.

Thanks for help guys.
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Old 10-14-2018, 03:22 AM
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I cleaned the MAF sensor, and ess just for kicks. Tested the coils and pulled the plugs. I found an odd looking coil which failed the bench test, A to B was 0.33 while the others read around 1.45. All the plugs looked mostly brown with a few carbon deposits. I was trying to find out if white spots on the bottom of the coil is bad or doesn't matter, but there is confusion as whether or not it matters. I didn't want to start the car until I replaced that strange coil. My leading coils are C type and the other trailing is a B type.

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Old 10-14-2018, 03:29 AM
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White spots aren't an indicator of anything per Mazda TSB.


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Old 10-14-2018, 07:09 AM
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The AEM intake can be causing issues with your mass airflow sensor. This is turn can cause fuel trims to be a little wonky. To be honest, the original air box is designed for optimal power and should be left in place. If you read Racing Beat's writeup on their REVi intake you'll see how good the original air box is.

Poor mileage can also be a result of plugs, wires or coils. You are on the right track testing the coils and inspecting the plugs. When in doubt, replace them.

In regards to the coolant, the orange color could be either rust contaminated coolant or a universal type of coolant. Either way, its best to perform a thorough coolant flush and fill with Mazda's FL22 green coolant.
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Old 10-14-2018, 08:34 AM
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Do you have the mesh screens in the intake in front of the MAF? Eithout those (in good shape), the MAF could be misreading.
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Old 10-14-2018, 02:45 PM
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Originally Posted by mazdaverx7 View Post
The AEM intake can be causing issues with your mass airflow sensor. This is turn can cause fuel trims to be a little wonky. To be honest, the original air box is designed for optimal power and should be left in place. If you read Racing Beat's writeup on their REVi intake you'll see how good the original air box is.
AEM intake is the same as Mazdaspeed save for the logo slapped on it, so if properly installed, it shouldn't cause any issues, and it's one of the few intakes that actually give you more power, albeit only a small amount.

Originally Posted by Loki View Post
Do you have the mesh screens in the intake in front of the MAF? Eithout those (in good shape), the MAF could be misreading.
Is there a mesh screen inside the AEM unit?
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Old 10-14-2018, 06:14 PM
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Originally Posted by UnknownJinX View Post
AEM intake is the same as Mazdaspeed save for the logo slapped on it, so if properly installed, it shouldn't cause any issues, .
But ................ it does ! I've tuned maybe a dozen cars with the AEM intake . All of them needed the maf rescaled to avoid fuel trims that caused them to run too rich under load.
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Old 10-14-2018, 08:21 PM
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Originally Posted by mazdaverx7 View Post
The AEM intake can be causing issues with your mass airflow sensor. This is turn can cause fuel trims to be a little wonky. To be honest, the original air box is designed for optimal power and should be left in place. If you read Racing Beat's writeup on their REVi intake you'll see how good the original air box is.

Poor mileage can also be a result of plugs, wires or coils. You are on the right track testing the coils and inspecting the plugs. When in doubt, replace them.

In regards to the coolant, the orange color could be either rust contaminated coolant or a universal type of coolant. Either way, its best to perform a thorough coolant flush and fill with Mazda's FL22 green coolant.
Unfortunately, I bough the car with the intake already on and the PO didn't have the stock one. I will stock up on distilled water to flush the crap out of it. I have this prestone radiator flush that I used on my B2200. I wonder if it will be safe to use in the RX-8.

Originally Posted by Loki View Post
Do you have the mesh screens in the intake in front of the MAF? Eithout those (in good shape), the MAF could be misreading.
Originally Posted by UnknownJinX View Post
AEM intake is the same as Mazdaspeed save for the logo slapped on it, so if properly installed, it shouldn't cause any issues, and it's one of the few intakes that actually give you more power, albeit only a small amount.



Is there a mesh screen inside the AEM unit?
There are two mesh screens that looked completely clean, that I cleaned again along with the rubber boots.

Originally Posted by Brettus View Post
But ................ it does ! I've tuned maybe a dozen cars with the AEM intake . All of them needed the maf rescaled to avoid fuel trims that caused them to run too rich under load.
The long term fuel trim reads 0 when I am cruising, Next time I drive I'll pay more attention to the short term, but I only remember seeing small fluctuations in that one last time.
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Old 10-15-2018, 12:10 AM
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I was able to take the car for a drive that was cut short because I thought that I had blown a tire or shock. Before I drove, I took a look under the hood and I think I can hear a faint hiss but I am not entirely sure. The LTFT did improve quite a bit in the short drive. The LTFT and STFT read 0 while holding at 65 on the freeway. At idle the LTFT is at -7 and the vaccum is up to 13-14, that may be from reassembling the intake. This screenshot is at idle now.



The bumpy ride is from some lug nuts somehow flying off, I think. I never touched the tires since I got the car. My universal Craftsman set doesn't seem to be able to grab these type of lug nuts.


What do I need to remove these?
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Old 10-15-2018, 06:37 AM
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Those are aftermarket type locking lug nuts. The socket for those is pretty common and shouldn't give you a ton of trouble find one.

As far as cooling system cleaner is concerned, I use BG's Super Flush and it works wonders. Its very very good stuff. I have plenty in stock if you need any.

How much of a stock air box do you have left if anything?
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Old 10-15-2018, 04:18 PM
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Originally Posted by mazdaverx7 View Post
Those are aftermarket type locking lug nuts. The socket for those is pretty common and shouldn't give you a ton of trouble find one.

As far as cooling system cleaner is concerned, I use BG's Super Flush and it works wonders. Its very very good stuff. I have plenty in stock if you need any.

How much of a stock air box do you have left if anything?
There is nothing left of the air box. I bought the car with the intake already in it. I asked if they had the stock box but the PO also got the car like that.

How much for some of that flush? I was going to get about 10-15 gallons of distilled water and use that extra prestone flush, but I read somewhere that the coolant seals are sensitive.

Also, I am hoping nothing got damaged from driving the car like that. I probably drove 1 mile on the freeway then like 2.5 blocks with only 2 lug nuts.
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Old 10-15-2018, 04:23 PM
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2 lugs nuts? I would check that they're the right thread pitch. Losing one is unusual. Losing 3 is indicative of a deeper issue.

If those 2 were snug you're probably fine. If they were also loose the wheel studs could have been bent.
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Old 10-15-2018, 11:30 PM
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Originally Posted by Loki View Post
2 lugs nuts? I would check that they're the right thread pitch. Losing one is unusual. Losing 3 is indicative of a deeper issue.

If those 2 were snug you're probably fine. If they were also loose the wheel studs could have been bent.
The two that were left were a bit loose, but the hub looks fine, just rusty. The lug nuts were M12-1.5, same as the ones Google told me to buy. I don't know what could have happened. I know that before I purchased the car the auto broker had the rear shocks or whatever changed. Maybe they put them too tight or not tightened in the right pattern.



This car has been a pain since I bought it lol. The day I drove it home, the a/c flooded the passenger floorboard and started to drip on the driver side. Got stuck because the starter wire came loose. Then all these new issues. Will it ever end? Even for a moment, so I can actually enjoy driving the car.
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Old 10-16-2018, 02:03 AM
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Originally Posted by Brettus View Post
But ................ it does ! I've tuned maybe a dozen cars with the AEM intake . All of them needed the maf rescaled to avoid fuel trims that caused them to run too rich under load.
Thanks for that info. Guess I am glad that I didn't just grab an AEM then.

Not that I am really considering it anyway since CAN$500 for like 3 horses doesn't exactly spell value to me. It's not like the intake is badly designed and I like being able to slip under the radar if needed.

Originally Posted by Kakashi View Post
The two that were left were a bit loose, but the hub looks fine, just rusty. The lug nuts were M12-1.5, same as the ones Google told me to buy. I don't know what could have happened. I know that before I purchased the car the auto broker had the rear shocks or whatever changed. Maybe they put them too tight or not tightened in the right pattern.



This car has been a pain since I bought it lol. The day I drove it home, the a/c flooded the passenger floorboard and started to drip on the driver side. Got stuck because the starter wire came loose. Then all these new issues. Will it ever end? Even for a moment, so I can actually enjoy driving the car.
Let me fill you in on what could have happened:

My boss at my previous job told me that he was driving on a local highway one day with his family(wife and 2 daughters), and there was a car that in front of them that had a wheel fly off. The car immediately veered to the side with sparks flying everywhere. The wheel that flew off actually went just a hair above his truck. He and his entire family were that close to seeing the Grim Reaper...

This is why I try to minimize the times to have shops take off my wheels, and overtightening is a big pain as well. I remember helping a friend take off his wheels and one lug nut must have had 200+ lb.ft of torque on it because it was a massive PITA to take it off. Some people also have lug bolts snap because of overtightening.

So do yourself a big favour and buy a torque wrench, or at least lend one from an auto store until Black Friday(when they are like 50% off).

And what do you mean by A/C flooded? The condensed water didn't drain out and came out of the vents, or the refrigerant is leaking?

Your car doesn't sound like it was taken care of the best. Feel free to ask for help.
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Old 10-16-2018, 06:18 AM
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Originally Posted by Kakashi View Post
How much for some of that flush? I was going to get about 10-15 gallons of distilled water and use that extra prestone flush, but I read somewhere that the coolant seals are sensitive.
Shoot me a pm with your address and I'll get some out to you.
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Old 10-16-2018, 05:13 PM
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Originally Posted by UnknownJinX View Post
Thanks for that info. Guess I am glad that I didn't just grab an AEM then.

Not that I am really considering it anyway since CAN$500 for like 3 horses doesn't exactly spell value to me. It's not like the intake is badly designed and I like being able to slip under the radar if needed.



Let me fill you in on what could have happened:

My boss at my previous job told me that he was driving on a local highway one day with his family(wife and 2 daughters), and there was a car that in front of them that had a wheel fly off. The car immediately veered to the side with sparks flying everywhere. The wheel that flew off actually went just a hair above his truck. He and his entire family were that close to seeing the Grim Reaper...

This is why I try to minimize the times to have shops take off my wheels, and overtightening is a big pain as well. I remember helping a friend take off his wheels and one lug nut must have had 200+ lb.ft of torque on it because it was a massive PITA to take it off. Some people also have lug bolts snap because of overtightening.

So do yourself a big favour and buy a torque wrench, or at least lend one from an auto store until Black Friday(when they are like 50% off).

And what do you mean by A/C flooded? The condensed water didn't drain out and came out of the vents, or the refrigerant is leaking?

Your car doesn't sound like it was taken care of the best. Feel free to ask for help.
I borrowed a crappy harbor freight torque wrench. It has a Max of 80 but I think you can keep turning it to set to around 100. I set it to 90ft/lbs even I read that it was supposed to be 108 or 87. It should be enough.

I meant that turning on the a/c caused the passenger floorboard to be soaked. I only noticed because during a turn my leg got soaked. I looked for those "duck lips" and cleaned them, then I connected 4 straws and blew into it and more water came out lol.

I think the next thing I need to do is check the vaccum lines. I found a picture of them. Do I have to remove the black thing near the oil filler hole to see them to visually inspect them? I read that the vaccum at idle should be close to 20in/hg and maybe as low as 15-16in/hg on a more worn engine.
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