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Engine misfire above 3500rpm's
13 Aug 2023 21:22 - 14 Aug 2023 17:53 #250281
by 1900
Engine misfire above 3500rpm's was created by 1900
This has a G10T engine. Three-cylinder EFI Turbo no vacuum advance.
Looking for suggestions on what could cause what feels like a misfire that starts at 3500 rpms. It feels like the ignition is turned off and immediately right back on again and again. It must be half throttle all the way to full throttle. I have replaced the distributor complete, cap, wires, spark plugs, and coil. I have checked the fuel pressure, 35 psi, and under boost, 55 psi. I checked the fuel volume. I have checked for codes, but no codes. I can’t find a crankshaft or cam sensor. Any help or suggestions would be great. Thank you.
Looking for suggestions on what could cause what feels like a misfire that starts at 3500 rpms. It feels like the ignition is turned off and immediately right back on again and again. It must be half throttle all the way to full throttle. I have replaced the distributor complete, cap, wires, spark plugs, and coil. I have checked the fuel pressure, 35 psi, and under boost, 55 psi. I checked the fuel volume. I have checked for codes, but no codes. I can’t find a crankshaft or cam sensor. Any help or suggestions would be great. Thank you.
Last edit: 14 Aug 2023 17:53 by 1900.
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13 Aug 2023 22:24 #250283
by Scimike
Yokohama Geolanders, Sony head unit, NAUTILUS Air Horn, DRL conversion, Rear cargo space, Elvis Bobblehead, transfer Guard, Indian hanging Elephant, Koni Heavy track dampers, Custom SS exhaust, Voodoo Doll, Adventure Rack with LED ight bar, vintage ERIBA caravan usually attached (yes it's slow)
Replied by Scimike on topic Engine misfire above 3500rpm's
What Jimny is this?
Distributor and boost suggest it's different than the majority on here.
If it actually has a distributor try fitting a wire between the plate on which the (points?) are mounted and the bottom plate. The bottom plate is fixed (and earthed), the top plate sides with the vacuum advance. You can get intermittent earth connection between the two plates with age, a flexible bridging wire cures this. This is just a generic "classic car" fix for similar symptoms and may, or may not be applicable in this situation. But worth a mention just in case, I'll now shut up as I only know classics or my M13A
Distributor and boost suggest it's different than the majority on here.
If it actually has a distributor try fitting a wire between the plate on which the (points?) are mounted and the bottom plate. The bottom plate is fixed (and earthed), the top plate sides with the vacuum advance. You can get intermittent earth connection between the two plates with age, a flexible bridging wire cures this. This is just a generic "classic car" fix for similar symptoms and may, or may not be applicable in this situation. But worth a mention just in case, I'll now shut up as I only know classics or my M13A
Yokohama Geolanders, Sony head unit, NAUTILUS Air Horn, DRL conversion, Rear cargo space, Elvis Bobblehead, transfer Guard, Indian hanging Elephant, Koni Heavy track dampers, Custom SS exhaust, Voodoo Doll, Adventure Rack with LED ight bar, vintage ERIBA caravan usually attached (yes it's slow)
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14 Aug 2023 13:18 #250294
by DrRobin
2020 blue SZ5 (one of the last to be registered in the UK)
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog
Replied by DrRobin on topic Engine misfire above 3500rpm's
Looking at the description and a quick Google suggests this will be from the early 1990s. The turbo engine was probably originally for the Japanese market.
When an engine revs higher it puts more of a demand on the electrical system especially the coil and leads, but you appear to have replaced all of that.
The low tension side (12V) might still be a bit weak and just can't supply enough power at the increased revs.
Then there is the fuel side, not enough fuel at the higher revs, but I assume you checked that as well. Then there is air flow, is there a blockage?
If there is no vacuum advance then the timing should be the same all the way up the range, is it correct?
What about fuel octane rating, could that be OK at low boost levels but not high enough at higher levels of boost?
Finally it could be the ecu (if there is one) or one of the sensors which isn't adjusting correctly.
If you are certain on the ignition and fuel then that only leaves ECU, low tension side (12V) (possibly alternator/weak battery), air flow restriction or possibly a sensor (if it has many) giving the ecu a false reading.
Perhaps someone with a later turbo engine might be able to assist?
Hope that helps
Robin
When an engine revs higher it puts more of a demand on the electrical system especially the coil and leads, but you appear to have replaced all of that.
The low tension side (12V) might still be a bit weak and just can't supply enough power at the increased revs.
Then there is the fuel side, not enough fuel at the higher revs, but I assume you checked that as well. Then there is air flow, is there a blockage?
If there is no vacuum advance then the timing should be the same all the way up the range, is it correct?
What about fuel octane rating, could that be OK at low boost levels but not high enough at higher levels of boost?
Finally it could be the ecu (if there is one) or one of the sensors which isn't adjusting correctly.
If you are certain on the ignition and fuel then that only leaves ECU, low tension side (12V) (possibly alternator/weak battery), air flow restriction or possibly a sensor (if it has many) giving the ecu a false reading.
Perhaps someone with a later turbo engine might be able to assist?
Hope that helps
Robin
2020 blue SZ5 (one of the last to be registered in the UK)
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog
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14 Aug 2023 17:57 #250298
by 1900
Replied by 1900 on topic Engine misfire above 3500rpm's
This is a customers vehicle. I have no technical information on it. I don't even think the year is correct. It is my understanding that the Jimny is not legal in the U.S. I am looking for the crank or cam sensor and can't find either. I appreciate your reply.
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