Backfiring on hard acceleration. Only 4 cylinders being tested during KOER test


Fordranger1994

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Joined
Nov 8, 2019
Messages
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Location
Wisconsin
Vehicle Year
1994
Make / Model
Ford Ranger XLT
Engine Type
4.0 V6
Transmission
Automatic
2WD / 4WD
4WD
Tire Size
31x10.5
I have a 94 ranger 4.0 and on hard acceleration it begins to backfire really bad. If i ease into the throttle then floor it there is no back fire. As im cruising i also get a bad shudder/shaking until i floor it again and it goes away. I get no codes while testing KOEO and during the KOER It only tests 4 cylinders and code 538. I cant preform the cylinder balance test because no matter what when i start the test the rpms shoot up causing the code to show. I replaced the MAF sensor, ignition coil, spark plugs, the plug wires. It also only started happening when i filled it all the gas tank all the way up. Any help is greatly appreciated.
 


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