Bad MPG, possible low vaccum, orange coolant? - RX8Club.com

Go Back  RX8Club.com > General Topics > New Member Forum
Reload this Page >

Bad MPG, possible low vaccum, orange coolant?

New Member Forum A place for new members to get their feet wet

Bad MPG, possible low vaccum, orange coolant?

Reply

 
 
 
Old 10-11-2018, 10:05 PM
  #1  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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?
Kakashi is offline  
Reply With Quote
Old 10-11-2018, 10:22 PM
  #2  
Put it in "H"!
iTrader: (1)
 
Loki's Avatar
 
Join Date: Jun 2009
Location: Montreal
Posts: 3,986
Thanked 220 Times in 195 Posts
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.
Loki is offline  
Reply With Quote
Old 10-11-2018, 10:39 PM
  #3  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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.



Kakashi is offline  
Reply With Quote
Old 10-12-2018, 04:27 PM
  #4  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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.


Kakashi is offline  
Reply With Quote
Old 10-12-2018, 04:39 PM
  #5  
转子之魂
 
UnknownJinX's Avatar
 
Join Date: Apr 2017
Location: Victoria, BC
Posts: 1,468
Thanked 196 Times in 180 Posts
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?
UnknownJinX is offline  
Reply With Quote
Old 10-12-2018, 04:54 PM
  #6  
Put it in "H"!
iTrader: (1)
 
Loki's Avatar
 
Join Date: Jun 2009
Location: Montreal
Posts: 3,986
Thanked 220 Times in 195 Posts
Have you cleaned your MAF?
Loki is offline  
Reply With Quote
Old 10-12-2018, 04:59 PM
  #7  
Boosted Kiwi
iTrader: (2)
 
Brettus's Avatar
 
Join Date: Apr 2006
Location: Y-cat-o NZ
Posts: 18,061
Thanked 169 Times in 127 Posts
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 ?
Brettus is offline  
Reply With Quote
Old 10-12-2018, 07:28 PM
  #8  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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.
Kakashi is offline  
Reply With Quote
Old 10-14-2018, 02:22 AM
  #9  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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.

Kakashi is offline  
Reply With Quote
Old 10-14-2018, 02:29 AM
  #10  
转子之魂
 
UnknownJinX's Avatar
 
Join Date: Apr 2017
Location: Victoria, BC
Posts: 1,468
Thanked 196 Times in 180 Posts
White spots aren't an indicator of anything per Mazda TSB.


Last edited by UnknownJinX; 10-14-2018 at 02:32 AM.
UnknownJinX is offline  
Reply With Quote
Old 10-14-2018, 06:09 AM
  #11  
RX-Heaven
iTrader: (6)
 
mazdaverx7's Avatar
 
Join Date: Sep 2008
Location: Vermilion Ohio
Posts: 1,424
Thanked 20 Times in 19 Posts
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.
mazdaverx7 is online now  
Reply With Quote
Old 10-14-2018, 07:34 AM
  #12  
Put it in "H"!
iTrader: (1)
 
Loki's Avatar
 
Join Date: Jun 2009
Location: Montreal
Posts: 3,986
Thanked 220 Times in 195 Posts
Do you have the mesh screens in the intake in front of the MAF? Eithout those (in good shape), the MAF could be misreading.
Loki is offline  
Reply With Quote
Old 10-14-2018, 01:45 PM
  #13  
转子之魂
 
UnknownJinX's Avatar
 
Join Date: Apr 2017
Location: Victoria, BC
Posts: 1,468
Thanked 196 Times in 180 Posts
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?
UnknownJinX is offline  
Reply With Quote
Old 10-14-2018, 05:14 PM
  #14  
Boosted Kiwi
iTrader: (2)
 
Brettus's Avatar
 
Join Date: Apr 2006
Location: Y-cat-o NZ
Posts: 18,061
Thanked 169 Times in 127 Posts
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.
Brettus is offline  
Reply With Quote
Old 10-14-2018, 07:21 PM
  #15  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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.
Kakashi is offline  
Reply With Quote
Old 10-14-2018, 11:10 PM
  #16  
Registered
Thread Starter
 
Join Date: Sep 2018
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
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?
Kakashi is offline  
Reply With Quote
Old 10-15-2018, 05:37 AM
  #17  
RX-Heaven
iTrader: (6)
 
mazdaverx7's Avatar
 
Join Date: Sep 2008
Location: Vermilion Ohio
Posts: 1,424
Thanked 20 Times in 19 Posts
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?
mazdaverx7 is online now  
Reply With Quote
Reply
 
 
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
JDM
Series I Trouble Shooting
29
10-01-2010 04:50 PM
OfficerFarva
Series I Major Horsepower Upgrades
21
05-06-2006 03:23 PM
simo
Series I Tech Garage
89
10-24-2005 08:12 PM
bcrothers
RX-8 Discussion
5
05-03-2004 08:56 AM


Thread Tools
Search this Thread
Rate This Thread
Rate This Thread: