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jeep stumbles and backfires out the intake after it warms up???

Old 06-09-2011, 09:15 PM
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Default jeep stumbles and backfires out the intake after it warms up???

jeep runs fine when its cold, as soon as it warms up it starts to run bad and just falls on its face if you give it gas, it will also backfire out the intake
. the higher rpm are not as bad but down low its bad. what could it be??
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Old 06-10-2011, 06:11 AM
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How old is the oxygen sensor?

When the engine first starts, it uses "default" fuel/air ratio, but not for long. Very quickly, it turns part of that job over to the engine management system, which would include the oxygen sensor and the map sensor, so those are two primary suspects IF it runs good for a very short time after starting a cold engine.

The map sensor can be tested, and so can the oxygen sensor, but you need specialized equipment and knowhow. If the O2 sensor has more than 100k on it, replace it. I look for NTK brand oxygen sensors. ebay = noway for sensors, unless the brand is confirmed. No lack of complete crap floating around on ebay.
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Old 06-10-2011, 07:43 AM
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New o2 sensor, I'll check the map sensor tonight
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Old 06-11-2011, 11:49 PM
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Smile O2 sensor and Map sensor stops the backfiring

These two inexpensive items did wonders for my 91 Jeep...Now I have a good running jeep with a higher NOX....The station put K44 and two shots of fuel injector fluid in..Now what do I do? Is this supposed to be a new thread? Newbie
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