Help! Irregular idle, AFR running lean, No leaks?

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Isaacm
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Hey.  They are NOT Training wheels.
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Help! Irregular idle, AFR running lean, No leaks?

Post by Isaacm » Fri Jan 27, 2017 7:45 pm

Lately iv been having a few symptoms with my 1992 Turboed MX5.
Ill list the symptoms and if anyone could help me diagnose the problem that would be great!

Symptoms:
1. On startup the car has major hesitation and sometimes cant even get up hills in first gear.

2. Wide band AFR is reading Lean 18-20 constantly.
(i just changed the Wideband sensor too)

3. I did a smoke leakdown test, and there are no leaking Vacuum hoses or leaks in the exhaust.

4. The idle is intermittent, Either it runs perfectly at 850rpm or it goes down to 300 and stays there.

5. I checked the idle control screw (GRND and TEN) and it goes floats at 850rpm

6. The mx5 is generally just hesitant and not as preppy as it normally is. Lack of power, and closed loop operation never is close to 14.6

Any help would be greatly appreciated!

2low2c
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Post by 2low2c » Sat Jan 28, 2017 7:15 am

what ecu are you using ?

jif
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Help! Irregular idle, AFR running lean, No leaks?

Post by jif » Sat Jan 28, 2017 9:31 am

Hi Isaac.  Hard to say without knowing your setup but here's a wild guess... 


1 and 6 sound like spark plug wires. Or plugs...  Or coils. 


4 could be the idle switch.


Does the wide band need calibrating? Or the ecu lookup tables aren't  right.  See what it says in free air...  As the engine basically won't run with a 20:1 AFR !  I experimented with lean running and even 16:1 was at the ragged edge. 


I won't get into the ecu... Way too much unknowns there!! 


Cheers
Jeff (former turbo '96 owner) 

On Jan 27, 2017 7:45 PM, "Isaacm" <mx5talk@mx5forum.co.nz (mx5talk@mx5forum.co.nz)> wrote:
Lately iv been having a few symptoms with my 1992 Turboed MX5.
Ill list the symptoms and if anyone could help me diagnose the problem that would be great!

Symptoms:
1. On startup the car has major hesitation and sometimes cant even get up hills in first gear.

2. Wide band AFR is reading Lean 18-20 constantly.
(i just changed the Wideband sensor too)

3. I did a smoke leakdown test, and there are no leaking Vacuum hoses or leaks in the exhaust.

4. The idle is intermittent, Either it runs perfectly at 850rpm or it goes down to 300 and stays there.

5. I checked the idle control screw (GRND and TEN) and it goes floats at 850rpm

6. The mx5 is generally just hesitant and not as preppy as it normally is. Lack of power, and closed loop operation never is close to 14.6

Any help would be greatly appreciated![/b]





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Isaacm
Hey. They are NOT Training wheels.
Hey.  They are NOT Training wheels.
Posts: 2
Joined: Fri Jan 27, 2017 7:43 pm

Post by Isaacm » Mon Jan 30, 2017 12:51 am

To add onto my setup:
Its a 1992 Mx5, Running a TD04 Greddy kit, Custom intake and exhuast.
Wideband is a Plex sensor which is emulating a narrowband to the Stock ECU.
Leaving the engine off, and turning the IGN on, the Wideband reads AIR.

The Engine managment is a piggyback Emanage Blue with and 4bar map input into it.

It has 330 supra injectors.

I have also changed my spark plug wires to new NGK blues.

I have recently pluged my stock o2 sensor in to diagnose whether it was faulty emulation but the problem still persisted.

The idle switch under the clutch i repaired a few months ago.
Attachments
20161222_134733.jpg
Engine
OLDcPJL.jpg
SparkPlug Colour

mx5number99
Hey. They are NOT Training wheels.
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Post by mx5number99 » Thu Feb 02, 2017 10:03 pm

Since I'm hoping to dabble in a turbo shortly - what's your PCV hooked up to? Its the only part of the plumbing which doesn't make sense to me in that picture.

Also - our car did some similar things when the bung in the throttle bypass hose came out. I'm not saying that's your issue - it should mean you get a lower AF ratio when in boost. but might be something to check.

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