Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by: KPower

My Miata occasionally goes lean under boost

Thread Tools
 
Search this Thread
 
Old 09-01-2013, 05:12 PM
  #1  
Newb
Thread Starter
 
CAF92's Avatar
 
Join Date: Aug 2013
Posts: 8
Total Cats: -8
Default My Miata occasionally goes lean under boost

Hey everyone, Im new to the whole forum thing and I need some help with my car. I have a 99 1.8l miata with a Jr supercharger running 5psi on a stock ecu. From the looks of things under the hood, this install was done by an amateur at home.
Now for my issues; about six months after I bought it, it would occasionally fall flat on its face under boost even when it only hits 3psi or less. I originally thought the fuel pump was going bad so I replaced it with a new high flow pump and I still had the issue, so then came a new fuel filter, still with no result. It has also been throwing a code for the IAT sensor but I'm not sure if that would cause the issues that Im having. Any help would be very appreciated
CAF92 is offline  
Old 09-01-2013, 05:26 PM
  #2  
Senior Member
iTrader: (2)
 
Onyxyth's Avatar
 
Join Date: May 2013
Location: Boyertown, PA
Posts: 735
Total Cats: 62
Default

IAT could very well be the problem.

But running boost on the stock ECU is bad and you should feel bad.
Onyxyth is offline  
Old 09-01-2013, 05:29 PM
  #3  
Moderator
iTrader: (12)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,647
Total Cats: 3,009
Default

Bad IAT sensor could cause a lean condition.
sixshooter is offline  
Old 09-01-2013, 05:33 PM
  #4  
Moderator
iTrader: (12)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,647
Total Cats: 3,009
Default

Have you ever heard of an O2 clamp? Search for it on this forum and see if it matches your symptoms.

But for your sake, get an MS3 Basic from Reverent.
sixshooter is offline  
Old 09-01-2013, 09:39 PM
  #5  
Newb
Thread Starter
 
CAF92's Avatar
 
Join Date: Aug 2013
Posts: 8
Total Cats: -8
Default

Originally Posted by sixshooter
Have you ever heard of an O2 clamp? Search for it on this forum and see if it matches your symptoms.

But for your sake, get an MS3 Basic from Reverent.
Okay thanks for the info. As for the MS3, I cant find the price on one or a place to buy it any info there would be appreciated. And about the o2 clamp, I cant find it ether.
CAF92 is offline  
Old 09-02-2013, 12:43 AM
  #6  
Former Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,099
Default

You do realize that running 5psi on a stock ECU with no added fuel is a great way to blow up the motor, right?
Savington is offline  
Old 09-02-2013, 06:40 AM
  #7  
Moderator
iTrader: (12)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,647
Total Cats: 3,009
Default

Originally Posted by CAF92
Okay thanks for the info. As for the MS3, I cant find the price on one or a place to buy it any info there would be appreciated. And about the o2 clamp, I cant find it ether.
MS Labs is in the vendor section.

O2 clamp is in a sticky at the top of the parts for sale section.
sixshooter is offline  
Old 09-03-2013, 08:10 PM
  #8  
Newb
Thread Starter
 
CAF92's Avatar
 
Join Date: Aug 2013
Posts: 8
Total Cats: -8
Default

Originally Posted by Savington
You do realize that running 5psi on a stock ECU with no added fuel is a great way to blow up the motor, right?
Its a stock ecu yes, but it is the old style jr supercharger kit so pre power card. It gets plenty of fuel whenever my weird issue isn't hindering it. And whenever that happens I don't let it go into boost.
CAF92 is offline  
Old 09-03-2013, 09:09 PM
  #9  
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 10,453
Total Cats: 1,796
Default

Pooooowwwweeeeerrrrrrrrcardddddddddd.


What happens to the afrs when it "falls flat on its face"?
triple88a is offline  
Old 09-05-2013, 09:20 AM
  #10  
Boost Czar
iTrader: (62)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,490
Total Cats: 4,079
Default

how do you even know it's going lean?
Braineack is offline  
Old 09-05-2013, 09:45 AM
  #11  
I'm a terrible person
iTrader: (19)
 
FRT_Fun's Avatar
 
Join Date: Apr 2009
Location: Arizona
Posts: 7,174
Total Cats: 180
Default

Obviously "falls flat on it's face" = "lean" duh.
FRT_Fun is offline  
Old 09-05-2013, 10:02 AM
  #12  
Boost Czar
iTrader: (62)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 79,490
Total Cats: 4,079
Default

oh. I thought that was just what a JR45 felt like.
Braineack is offline  
Old 09-05-2013, 10:24 AM
  #13  
Moderator
iTrader: (12)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,647
Total Cats: 3,009
Default

Superchargers are a drag.
sixshooter is offline  
Old 09-05-2013, 11:15 AM
  #14  
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 10,453
Total Cats: 1,796
Default

Just a shot in the dark here but i betcha the OP has no wideband :P
triple88a is offline  
Old 09-05-2013, 11:41 AM
  #15  
Senior Member
 
Mazduh's Avatar
 
Join Date: Mar 2011
Location: South Chicago
Posts: 697
Total Cats: 26
Default

Mazduh is offline  
Old 09-06-2013, 10:24 PM
  #16  
Newb
Thread Starter
 
CAF92's Avatar
 
Join Date: Aug 2013
Posts: 8
Total Cats: -8
Default

Yup, Correct. No wide band, yet. I do have the "red, yellow, green" waving led type AFR gage(cant think of what it is called at the moment) I have a new IAT sensor coming to me tomorrow. Really hoping that solves my issue.
CAF92 is offline  
Old 09-06-2013, 10:28 PM
  #17  
Newb
Thread Starter
 
CAF92's Avatar
 
Join Date: Aug 2013
Posts: 8
Total Cats: -8
Default

Originally Posted by sixshooter
Superchargers are a drag.
No joke there, in more ways than one. A turbo is what I really want, but sadly, it isn't in the budget.
CAF92 is offline  
Old 09-06-2013, 10:40 PM
  #18  
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 10,453
Total Cats: 1,796
Default

Where does the red yellow and green waving gauge take its signal from if you dont have a wideband?
triple88a is offline  
Old 09-06-2013, 10:45 PM
  #19  
Moderator
iTrader: (12)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 20,647
Total Cats: 3,009
Default

Originally Posted by CAF92
Yup, Correct. No wide band, yet. I do have the "red, yellow, green" waving led type AFR gage(cant think of what it is called at the moment)
It's called garbage. It would benefit you more to pipe the exhaust gas into the cabin and try to sniff it to determine if you were rich or lean and by how much. Be sure to do this with all of the windows rolled up or it won't be as accurate.
sixshooter is offline  
Old 09-06-2013, 11:56 PM
  #20  
Elite Member
iTrader: (2)
 
triple88a's Avatar
 
Join Date: Apr 2006
Location: Chicago, IL
Posts: 10,453
Total Cats: 1,796
Default

Originally Posted by sixshooter
It's called garbage. It would benefit you more to pipe the exhaust gas into the cabin and try to sniff it to determine if you were rich or lean and by how much. Be sure to do this with all of the windows rolled up or it won't be as accurate.
Definitely legit method. I also use a vice grip on my fuel line to adjust my afrs.
triple88a is offline  


Quick Reply: My Miata occasionally goes lean under boost



All times are GMT -4. The time now is 01:55 AM.