Code P0135, runs rough?

2002 JEEP WRANGLER
110,000 MILES • 4.0L • 6 CYL • 4WD • MANUAL
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CLINT JANES
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My vehicle runs really rough. I originally thought it was the O2 sensors, so I took it to a shop and spent $1,500.00 for sensors, spark plugs, fuel pump, and injectors just to get it back and it runs no different than when I dropped it off. I put a new crank position sensor on it myself and that didn’t help at all either. It hasn’t thrown a code at all till last night and it gave me a P0135 code. I’m out of ideas. Any suggestions?
Oct 3, 2022 at 7:10 AM
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STRAILER
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The code P0135 is O2 sensor heater circuit bank 1 sensor 1. so, that will not make the engine run rough, but you do need to replace the sensor. Are there no other codes? If not, we need to do a compression test, while you have the spark plugs out look at their condition the spark plugs that look different will be the cylinder that is having the problem. here is a guide to help you with the job, you can rent the gauge from the auto parts store for cheap or free. You can just upload a short video of the engine cranking over and I can tell if the compression is okay as well.

https://www.2carpros.com/articles/how-to-test-engine-compression

Let us know what happens and please upload pictures or videos of the problem.
Oct 3, 2022 at 4:01 PM
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CLINT JANES
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Ken L. No other codes at all. I did already did a compression test and every cylinder read 150. I pulled the plugs and replaced all of them with new double platinum's. I drove it a couple of miles and pulled them again and cylinders 2 and 3 were very black.
Oct 4, 2022 at 9:08 AM
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STRAILER
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Nice work, I would replace the #2- and #3-cylinders fuel injectors.

Here is a generic guide to show you how with instructions below to show you on your car:

https://www.2carpros.com/articles/how-to-replace-a-fuel-injector

Check out the images (below). Please let us know what happens. Don't forget to replace the oxygen sensor.


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Oct 4, 2022 at 3:57 PM
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CLINT JANES
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I should have mentioned it, but I already changed the injectors also. Is it possible to have a weak spark off the ignition coil? I have spark on every plug, but I’ve had a couple of people tell me it can have a weak spark.
Oct 5, 2022 at 9:24 AM
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STRAILER
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Yes, definitely a weak spark can cause the problem.
Oct 6, 2022 at 10:53 AM
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CLINT JANES
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with all the stuff I’ve changed already, would an ignition coil be what you tried next?
Oct 6, 2022 at 1:01 PM
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STRAILER
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Yep, that is where I was going next here is how you can change out the ignition coils in the images below. Check out the images (below). Please let us know what you find.
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Oct 7, 2022 at 3:25 PM
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CLINT JANES
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It was the ignition coil causing the problem. Thank you so much for your time. I really appreciate it.
Oct 7, 2022 at 8:31 PM
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STRAILER
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Good to hear, please use 2CarPros anytime we are here to help. Thanks for getting back to us.
Oct 8, 2022 at 10:02 AM