Engine backfires/sputters under load
Sep 27, 2023 | 10:37 AM
#1
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Engine backfires/sputters under load
Truck: 1985 Toyota Engine: 22REcTrans: Manual Issue: Car lacks power (less than the normal lack of power 
Things I have attempted thus far:
Quick video: https://u.pcloud.link/publink/show?c...BNoChUhQtROh8y
Things I have attempted thus far:- Replaced all spark plugs (all were in good shape, one had a good bit of black soot, but wasn't wet.
- Checked all spark plug wires. Unplugged each one and tested issue. Same issue with backfire/sputter no matter which spark plug was disconnected
- Checked rotor and cap, visually looks good, and if issue is happening no matter which spark plug is unplugged, prob not the issue.
- Sprayed starter fluid all over vacuum lines in search of a leak...nothing showed itself.
- Added a fresh tank of gas.
Quick video: https://u.pcloud.link/publink/show?c...BNoChUhQtROh8y
Last edited by 85Sunrader; Sep 27, 2023 at 10:45 AM.
Oct 12, 2023 | 06:49 AM
#2
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Joined: Jun 2016
Posts: 719
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From: Florida
Several suspects:
Spark Plug Gap - Did you set the plug gaps or just install them out of the box? Never trust the "factory gap", check 'em for yourself before installing. Spec is 0.031" or 0.8mm.
Plug Wires - How old are they? Just because they look OK doesn't mean much. You need to get an ohm meter and measure the resistance end to end to see if they are in spec. Most new plug wires for a 22R series engine fall in a range if 6K to 13K Ohms. Most new wires will average 12K ohms per foot.
Toyota specifies a maximum of 25K ohms. Anything over 17-18K I just replace the wires.
Considering that your issue is the same regardless of which spark plug wire is unplugged, that would make me look at the coil-to-distributor cap wire very hard. The coil-to-cap wire does 4 times the work of a single spark plug wire, & I have seen one go bad before plug wires do.
Again, test for resistance being out of spec. Any doubts replace with new quality wire(s).
Ignition Coil - Possibility that the coil is/has developed high resistance or may have a partial internal short. Again, test with an ohm meter. 1985 22R Series coil specs are Primary 0.4 to 0.5 Ohms, Secondary 8500 to 11,500 Ohms.
It would be very wise to check the coil's resistance after it's been run for a while, especially on the secondary side. Why? Because if any of the wire in the coil is breaking down/fatigued, you'll see a higher resistance reading when the wire is warm/hot.
This can also apply to plug & coil-to-cap wires.
NOTE: ALL wires must be disconnected from the coil to properly test it with an ohm meter.
If the coil Secondary measures 10,000 Ohms or more cold or hot, replace with a new quality coil.
If you do all this & still have the problem, the issue is elsewhere, perhaps with engine timing.
Spark Plug Gap - Did you set the plug gaps or just install them out of the box? Never trust the "factory gap", check 'em for yourself before installing. Spec is 0.031" or 0.8mm.
Plug Wires - How old are they? Just because they look OK doesn't mean much. You need to get an ohm meter and measure the resistance end to end to see if they are in spec. Most new plug wires for a 22R series engine fall in a range if 6K to 13K Ohms. Most new wires will average 12K ohms per foot.
Toyota specifies a maximum of 25K ohms. Anything over 17-18K I just replace the wires.
Considering that your issue is the same regardless of which spark plug wire is unplugged, that would make me look at the coil-to-distributor cap wire very hard. The coil-to-cap wire does 4 times the work of a single spark plug wire, & I have seen one go bad before plug wires do.
Again, test for resistance being out of spec. Any doubts replace with new quality wire(s).
Ignition Coil - Possibility that the coil is/has developed high resistance or may have a partial internal short. Again, test with an ohm meter. 1985 22R Series coil specs are Primary 0.4 to 0.5 Ohms, Secondary 8500 to 11,500 Ohms.
It would be very wise to check the coil's resistance after it's been run for a while, especially on the secondary side. Why? Because if any of the wire in the coil is breaking down/fatigued, you'll see a higher resistance reading when the wire is warm/hot.
This can also apply to plug & coil-to-cap wires.
NOTE: ALL wires must be disconnected from the coil to properly test it with an ohm meter.
If the coil Secondary measures 10,000 Ohms or more cold or hot, replace with a new quality coil.
If you do all this & still have the problem, the issue is elsewhere, perhaps with engine timing.
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