MX5 Turbo 1990 MS1 Lean AFR (Air leak???) - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 06-26-2014, 05:18 AM   #1
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default MX5 Turbo 1990 MS1 Lean AFR (Air leak???)

Hi everybody,

So recently I bought everything i needed to turbo my MX5, that includes ECU, Engine, Turbo the lot its even mapped and this engine has been running the same map for the past few years so everything should run perfect... But it does not.

Originally it would idle really bad, fluctuating a lot and also the AFR would read 17s even 18s and sometimes go off the guage, so we started looking for air leaks and found one right where the first silicone pipe connects to the turbo and this was fixed.

However the problem is still persisting just not as bad, it seems the idle is higher than it was before which was around 900rpm and now it sits about 1100RPM and fluctuates still but not as bad but I still have really lean AFR readings.

The AFR readings will go rich if i quickly apply the throttle and then go back lean, however if i slowly apply the throttle they will stay consistently lean.

So i did a little more digging and tryed to find some more leaks and noticed when i sprayed engine degreaser on one of the pipes the engine RPMs would rise and the AFR readings would read around 13-14.8...

So i switched over some clamps and still the same problem does this sound like a air leak to you guys?

Also i have attached a quick datalog file I dont know if it will be any use?

EDIT: IF i disconnect the IAT sensor it will run at about 10-13 on the ARF gauge and of course cause its so rich it hesistates when you hit boost.
Attached Files
File Type: msl 2014-06-26_07.49.17.msl (484.5 KB, 54 views)

Last edited by xXxKillDogxXx; 06-26-2014 at 05:35 AM.
xXxKillDogxXx is offline   Reply With Quote
Old 06-26-2014, 11:05 AM   #2
Junior Member
iTrader: (2)
 
Join Date: Jan 2007
Posts: 329
Total Cats: 16
Default

ok, why are you going into boost when you cna't even idle correctly? no-no

have you checked your IAC valve? it may be open hence why RPMs are so high at idle.

load a base map for your car after saving the updated one and see if that makes the car idle better.
you didn't state this, but are you running the WB to the ECU or are you using stock O2 to feed the eCU?
Alejo_NIN is offline   Reply With Quote
Old 06-26-2014, 11:09 AM   #3
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,192
Total Cats: 2,583
Default

boost leak test
18psi is offline   Reply With Quote
Old 06-26-2014, 03:04 PM   #4
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default

Quote:
Originally Posted by Alejo_NIN View Post
ok, why are you going into boost when you cna't even idle correctly? no-no

have you checked your IAC valve? it may be open hence why RPMs are so high at idle.

load a base map for your car after saving the updated one and see if that makes the car idle better.
you didn't state this, but are you running the WB to the ECU or are you using stock O2 to feed the eCU?
I had to drive it back from the garage so i had the IAT disconnected which made it run rich and its kinda hard not to hit boost haha.

I havnt checked the IAC no, what would be the best way to check it?

And im using a AEM UGO WB and gauge all going to the ECU and everything.

Quote:
Originally Posted by 18psi View Post
boost leak test
Would that make it run this lean though
xXxKillDogxXx is offline   Reply With Quote
Old 06-26-2014, 03:40 PM   #5
Elite Member
iTrader: (1)
 
Join Date: Jun 2014
Location: Austin, TX
Posts: 2,849
Total Cats: 271
Default

Quote:
Originally Posted by xXxKillDogxXx View Post
Would that make it run this lean though
Boost leak would be rich I believe, On boost + Leak = less air in = more fuel on WB read out

I had a knock off greddy bov with an o-ring seal on my turbo kit when purchased, car ran like crap, would run rich and die coming up to lights/stops.

With no adjustments to the map, the bov replacement was a night/day difference

I would check for vac leaks, due to the high idle. It could be pulling in air that isn't being seen through the ecu so you see high AFR all around.

Last edited by Girz0r; 06-26-2014 at 03:51 PM.
Girz0r is offline   Reply With Quote
Old 06-26-2014, 04:24 PM   #6
Elite Member
iTrader: (2)
 
Join Date: Aug 2012
Location: Indianapolis
Posts: 3,325
Total Cats: 235
Default

Do you run the AFM/MAF still? If you're running speed density I'm not sure why a boost leak would change your AFRs.

Check for pre-O2 sensor exhaust leaks while you're at it.
thenuge26 is offline   Reply With Quote
Old 06-26-2014, 04:36 PM   #7
Junior Member
iTrader: (2)
 
Join Date: Jan 2007
Posts: 329
Total Cats: 16
Default

you could have a leak at the exh manifold which is drawing in fresh air and making you run lean, worst case scenario is one injector not firing...are you sure all inj are firing?
this will cause a LEAN condition but no detonation because there is no gas at all.
Alejo_NIN is offline   Reply With Quote
Old 06-26-2014, 05:22 PM   #8
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default Leaks

Well when i rev the engine quickly is will get rich readings if I rev it slow the AFR will read lean just like it does at idle.

I suppose I could have a exhaust leak I'll see if I can find anything in a bit.

As for MAF I have removed that and replaced it with a IAT and map sensor.

The car is so close to running perfect just this little issue
xXxKillDogxXx is offline   Reply With Quote
Old 06-26-2014, 05:59 PM   #9
Elite Member
iTrader: (2)
 
Join Date: Aug 2012
Location: Indianapolis
Posts: 3,325
Total Cats: 235
Default

Yeah since you're running speed density, vacuum leaks affect much less than if you were still running with the MAF. My money is on an exhaust leak of some kind throwing off your O2 readings.

As for revving slowly vs quickly, when you rev quickly you're probably getting accel enrichments as your TPSDOT is hitting the threshold and adding fuel vs revving slowly and not stabbing the gas.
thenuge26 is offline   Reply With Quote
Old 06-26-2014, 06:38 PM   #10
Senior Member
 
Join Date: Aug 2010
Location: Arl. Texas
Posts: 937
Total Cats: 23
Default

What ECU are you using?

What injectors are you using?

What does "mapped" mean?
Miater is offline   Reply With Quote
Old 06-26-2014, 07:06 PM   #11
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default Setup

I'm running a megasquirt 1 with ev14 550cc injectors and the car has been fully mapped it was all taken from MX5 dans old car who runs universal inter coolers.

The car was running fine before swapping everything over to my shell so and it should be a straight swap since I have the full setup nothing has changed.

Thanks for all help btw guys it's greatly appreciated!
xXxKillDogxXx is offline   Reply With Quote
Old 06-26-2014, 11:19 PM   #12
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default Found a leak

Okay so found a leak on the manifold looks like the gasket is not sealing properly would this cause the symptoms I'm having ?
xXxKillDogxXx is offline   Reply With Quote
Old 06-26-2014, 11:20 PM   #13
Murderator
iTrader: (76)
 
18psi's Avatar
 
Join Date: Apr 2008
Posts: 36,192
Total Cats: 2,583
Default

yes. and its warped. proper mating surfaces don't need gaskets
18psi is offline   Reply With Quote
Old 06-26-2014, 11:43 PM   #14
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default ??

Okay well I'll get a new gasket on order and see if that corrects the issue, how exactly can you say its warped when it could be a bad gasket?

Btw the manifold is a Corksport Cast manifold, so its not exactly a **** manifold by any means so i would hope its not warped... But the gasket is not a decent one by any means.
xXxKillDogxXx is offline   Reply With Quote
Old 06-27-2014, 12:04 AM   #15
Elite Member
iTrader: (1)
 
Join Date: Jun 2014
Location: Austin, TX
Posts: 2,849
Total Cats: 271
Default

Quote:
Originally Posted by 18psi View Post
yes. and its warped. proper mating surfaces don't need gaskets
^This

Quote:
Originally Posted by xXxKillDogxXx View Post
Okay so found a leak on the manifold looks like the gasket is not sealing properly would this cause the symptoms I'm having ?
Possibly, is there any trace of carbon coming out the leak? My Begi heat shield had a nice black streak of build-up from months of rich/bad tune. The local shop who touched it last did a poor quality job, I now question if my turbo was ever serviced.
Girz0r is offline   Reply With Quote
Old 06-27-2014, 01:00 AM   #16
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default

Yeah there is carbon streaks and I let the car cool and sprayed so liquid on the gasket and it may as well sprayed it back at me so there is a leak for sure.

Could this cause a surging idle ?
xXxKillDogxXx is offline   Reply With Quote
Old 06-27-2014, 10:34 AM   #17
Elite Member
iTrader: (1)
 
Join Date: Jun 2014
Location: Austin, TX
Posts: 2,849
Total Cats: 271
Default

Quote:
Originally Posted by xXxKillDogxXx View Post
Yeah there is carbon streaks and I let the car cool and sprayed so liquid on the gasket and it may as well sprayed it back at me so there is a leak for sure.

Could this cause a surging idle ?
Not sure,

The only thing I can think of is if the manifold is leaking, not all air/fuel mix is hitting your o2 sensors and based off of that. Your ecu could be trying to 'fix' itself from being too rich if it's not seeing enough air. The mixture could be off and your ECU could be confused & unhappy

I would check for vac leaks after the manifold is fixed if you're still having idle surge issues.
Girz0r is offline   Reply With Quote
Old 06-27-2014, 11:23 AM   #18
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default

Quote:
Originally Posted by Girz0r View Post
Not sure,

The only thing I can think of is if the manifold is leaking, not all air/fuel mix is hitting your o2 sensors and based off of that. Your ecu could be trying to 'fix' itself from being too rich if it's not seeing enough air. The mixture could be off and your ECU could be confused & unhappy

I would check for vac leaks after the manifold is fixed if you're still having idle surge issues.
Could i possibly disconnect the Wideband and see if that changes anything?
xXxKillDogxXx is offline   Reply With Quote
Old 06-27-2014, 11:38 AM   #19
Elite Member
iTrader: (1)
 
Join Date: Jun 2014
Location: Austin, TX
Posts: 2,849
Total Cats: 271
Default

Quote:
Originally Posted by xXxKillDogxXx View Post
Could i possibly disconnect the Wideband and see if that changes anything?
If the WB is hooked into your megasquirt I wouldn't. I'd try fixing the manifold leak first, check for vac leaks 2nd if still high/surge idle.
Girz0r is offline   Reply With Quote
Old 06-27-2014, 12:00 PM   #20
Junior Member
Thread Starter
 
Join Date: Jun 2014
Location: Plymouth, UK
Posts: 106
Total Cats: 1
Default

Quote:
Originally Posted by Girz0r View Post
If the WB is hooked into your megasquirt I wouldn't. I'd try fixing the manifold leak first, check for vac leaks 2nd if still high/surge idle.
Okay well I have ordered a new gasket, some vacuum hose and some heat sheilding which should be here in the next few days, from what we have checked there is no more leaks in the piping just the exhaust leak now, as the car no longer sounds like its strugling to idle like it was before with the air leak its smooth but just surging a bit between 1000-1100rpm and the obvious lean AFR.

So hopefully the new gasket solves the issue.

Also if I have the manifold leak that means the car will have more boost once its fixed so should be a interesting test drive once its all fixed...
xXxKillDogxXx is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Garrett Turbo, 1.8 Oil Pan, & Misc. Stuff nbdooey Miata parts for sale/trade 9 08-30-2017 10:50 PM
Need help - Stock Balancer and Fastforward overlay pulleys Frank_and_Beans Supercharger Discussion 13 09-12-2016 09:17 PM
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM
VR6 to Miata Swap ScrapinMX5 Meet and Greet 8 09-28-2015 02:04 PM
why is my car running like pewp? (tune/datalog) itsMikey MSPNP 3 09-28-2015 07:40 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 04:45 AM.