'96 1.8 - Intermittently lean AFRs. Thoughts on order of checks?
08-16-2017, 10:13 AM
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'96 1.8 - Intermittently lean AFRs (Misfire?). Thoughts on order of checks?
Apologies, I have posted the same issue before (https://www.miataturbo.net/megasquir...ng-lean-92450/). I thought I had it solved, but it's reared it's head again 6 months later....
I've been having an intermittent poor running condition ('indicated' lean, ~17-19 on the MTX-L), where feels like it's running on 3 cylinders. It happened earlier in the year and I thought I had solved it with a replacement (used) coilpack. Recently it's started again, and now occurs at least once every journey, so I don't want to drive it any distance until I have some confidence that it's solved. I can't really replicate it in the drive.
I'm not expecting any magic answers, but thought you guys may have a view on priority of things to check. So far I have checked:
- Leads - New ones fitted, no difference.
- Coilpack (aftermarket) - New ones fitted, I thought this would solve it as it did last time, but the issue occurred on the first journey after fitting the new one!
- CAS - changed for used spare one I already had - no difference.
- Plugs, pulled these and ALL 4 were consistent and sooty. This confused me as it implies that problem is a) ignition, and b) across all four cylinders. I'm fitting new plugs tonight to see if I can see any difference clearer with the new ones.
- Compression. Just for peace of mind I checked all four cylinders, they're consistent and ~195-200 psi (dry).
Things remaining to check:
- Temp Sender - Rather than change it for no reason, I can check for erroneous results on the MS Logs.
- CAS - Presumably I can check CAS signal on the log as well.
- Fuel Pump? (connections? / blockages?). I would have thought it wouldn't run at all if the pump itself was gone.
- Injectors - New from FIC a couple of years ago, worth having them cleaned and flow checked?
- Fuel filter - new in Dec 2016. Worth changing again?
Is there anything else I could be checking to eliminate? I'm guessing a bit at the moment! I suppose the new coilpack could also be duff, but I can't really prove this. I'd likely be better off sorting out COPS than buying an OEM new one.
Thanks in advance!
Dave
I've been having an intermittent poor running condition ('indicated' lean, ~17-19 on the MTX-L), where feels like it's running on 3 cylinders. It happened earlier in the year and I thought I had solved it with a replacement (used) coilpack. Recently it's started again, and now occurs at least once every journey, so I don't want to drive it any distance until I have some confidence that it's solved. I can't really replicate it in the drive.
I'm not expecting any magic answers, but thought you guys may have a view on priority of things to check. So far I have checked:
- Leads - New ones fitted, no difference.
- Coilpack (aftermarket) - New ones fitted, I thought this would solve it as it did last time, but the issue occurred on the first journey after fitting the new one!
- CAS - changed for used spare one I already had - no difference.
- Plugs, pulled these and ALL 4 were consistent and sooty. This confused me as it implies that problem is a) ignition, and b) across all four cylinders. I'm fitting new plugs tonight to see if I can see any difference clearer with the new ones.
- Compression. Just for peace of mind I checked all four cylinders, they're consistent and ~195-200 psi (dry).
Things remaining to check:
- Temp Sender - Rather than change it for no reason, I can check for erroneous results on the MS Logs.
- CAS - Presumably I can check CAS signal on the log as well.
- Fuel Pump? (connections? / blockages?). I would have thought it wouldn't run at all if the pump itself was gone.
- Injectors - New from FIC a couple of years ago, worth having them cleaned and flow checked?
- Fuel filter - new in Dec 2016. Worth changing again?
Is there anything else I could be checking to eliminate? I'm guessing a bit at the moment! I suppose the new coilpack could also be duff, but I can't really prove this. I'd likely be better off sorting out COPS than buying an OEM new one.
Thanks in advance!
Dave
Last edited by ManicGTI; 08-18-2017 at 08:33 AM.
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08-17-2017, 07:46 AM
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Ok I'm new MLV, so please bear with me! I took some logs (when running well, and running badly) last week, symptoms are the same as I posted before:
- CAS - RPM trace is consistent, however Timing err% seems to be going up to ~5% during poor running. Should I be concerned with this?
- ECU Temp Sender - Likely ok as CLT is consistent, ~87-89 degC.
- IAT - Likely ok as MAT is consistent, when standing it starts to increase as I would expect, ~17-19 degC.
- CAS - RPM trace is consistent, however Timing err% seems to be going up to ~5% during poor running. Should I be concerned with this?
- ECU Temp Sender - Likely ok as CLT is consistent, ~87-89 degC.
- IAT - Likely ok as MAT is consistent, when standing it starts to increase as I would expect, ~17-19 degC.
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08-17-2017, 09:06 AM
#4
I' would change the fuel filter again . It may be a local fuel issue for me but I can't get more than two years out of a filter before it starts restricting fuel flow. I'd also temporarily install a fuel pressure gauge ( taped to the windshield) just to see if the fuel pump is keeping up under high demand. Fredb
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08-17-2017, 11:03 AM
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I've ordered a new (OEM) filter, however the current one is < year old, and only a few thousand miles on it.
Just a note, it doesn't seem dependant on the type of driving i'm doing. This morning it started running rough whilst sat stationary, in slow moving traffic. For obvious reasons i'm not running it hard at all at the moment.
Just a note, it doesn't seem dependant on the type of driving i'm doing. This morning it started running rough whilst sat stationary, in slow moving traffic. For obvious reasons i'm not running it hard at all at the moment.
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09-29-2017, 10:55 AM
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Sorry to bump this up again, but i'm at a loss at the moment :/
New OEM fuel filter installed, and I've taken a look at the pump for any loose connectors etc, nothing looks out of place.
I took a punt and converted to Toyota COPs anyway to try and eliminate the CoilPack and Leads (in case my non-OEM one was dodgy out of the box). In general it runs great, but on the way to work this morning the lean running kicked in again (albeit briefly).
Argh. Any thoughts?
New OEM fuel filter installed, and I've taken a look at the pump for any loose connectors etc, nothing looks out of place.
I took a punt and converted to Toyota COPs anyway to try and eliminate the CoilPack and Leads (in case my non-OEM one was dodgy out of the box). In general it runs great, but on the way to work this morning the lean running kicked in again (albeit briefly).
Argh. Any thoughts?
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