Misfire log, what to check next? MSPNP N/A car
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Car details.
92 Miata with 94 1.8(2001 bottom end) Intake Stock header exhaust MSPNP 90-93 no maf Misfire occurs most often between 5800-6200. Sometimes it'll get a blip at 5k. Very noticeable on the dyno graph. Changed coil, igniter, wires also tried adding grounds etc. Plugs are gaped correctly. Timing is staying true while watching with a timing light, however the light flickers differently during the misfire. Ive updated the firmware of the MSPNP, I have another PNP in another car im going to try also. Log is from a 4th gear pull on the dyno Thanks in advance! |
Sorry. Gotta ask the obvious question. You've changed pretty much everything else. Did you change the plugs? Sometimes they look perfectly fine, but aren't....
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Update:
Changed CAS Changed MSPNP moved grounds for coil and injectors.. Same issue. stefanst, The plugs are new and I've pulled them to inspect them and they look fine. I however just ordered another set from a local parts store and am going to swap them for a try. |
Something magical is happening at 6k rpm and 5k rpm....doesnt seem to happen anywhere else.
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What is the plug gap?
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Gap at .035 on new set of plugs was at .042 on last set. No change.
Anyone have a MAP for a 1.8 we can try, please post up. No meter. |
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Here is the MSQ we are currently using.
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Anyone?
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Please keep in mind that I have 0 experience running MS - I still am missing important engine parts.
But it looks like your MAP is all over the place. Almost 20% deviation. That may trigger enrichment and leaning out pretty much randomly. Also your O2 sensor doesn't seem to work... Of course I may be wrong! |
We're not using an O2 sensor, as for the map we pretty much put the car on the dyno to do WOT tuning first. Haven't spent much time on anything else.
I loaded a map from another 1.6(my old setup) car and added some fuel and it did the same thing in the same spot. Being we've swapped near everything I imagine it's a harness/resonance issue. One thing that seems odd to be is not only is the map flickering up and down, but so is the injector duty cycle during a pull. |
This is probably an obvious question and I'm a noob for asking it, but how did you log the misfires?
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did you ever changed out CAS or Crank angle sensor wire ? make sure it is shielded.
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The CAS sensor was extended but it appears to be with non shielded wire, never been an issue in other swaps I've done but defiantly worth a shot.
The car doesn't run a crank sensor. I'm going to try a few other simple things when I can get the car back on the dyno. I'll report back if we find it. |
Shielded wires fix my high rpm stumble.
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I'm seeing the AE trigger a lot at full throttle and some major MAP spikes. Where is the MAP sensor plumbed up to? You may need to try plumbing it to a different spot on this particular engine.
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Bell,
Which wires? Matt, I appreciate your reply, something so simple for us to not to think of trying. I hope to have the car back on the dyno tomorrow afternoon. I do believe its routed on one of the nipples under the 94-97 manifold, I'll have to check with the car owner as he installed the MS. |
I feel pretty confident that's it after thinking how the live gauges on the megatune are acting. The duty cycle jumping around etc....
:Crosses fingers: |
Its plumbed to the port on the firewall side bottom of the intake manifold next to EGR (usually caped except I think its used on Auto cars).) Will let you know tmw.
Thanks!! |
You might want to try putting it on a tee on the line to the fuel pressure regulator.
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Originally Posted by Matt Cramer
(Post 912383)
You might want to try putting it on a tee on the line to the fuel pressure regulator.
Thank You Sir. Moved that reference line for the MAP and all problems cured. |
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