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RUIDOSO JAMES 08-08-2013 12:24 AM

2006 jeep liberty check engine light on
I replaced my catalytic converters with a new set of direct fit cats about a month ago. At that time i also replaced all four o2 sensors with bosch sensors. The next day, the check engine light came on. Took it in to have the codes read. The only code that its showing is 0300, multiple cylinder misfires. The engine has 130,000 miles with all scheduled maintenance performed on time. I have new spark plugs in it as well. The mechanic is saying i should change my coil packs. This will cost over $150.00, and i'm not convinced that it is the problem. I think there is something from replacing the catalytic converters that has caused the light to go on, as the light has never come on since i bought it new in 2006. One other thing it just started doing, it is hesitating when you press the gas pedal. Not all the time, but occasionally.(i'm thinking this could be caused by the o2 sensors) check engine light turns off after a while, but comes back on each day. The majority of the time it is running perfect. This is so confusing. Not sure what to do from here.

Frango100 08-08-2013 01:26 AM

Re: 2006 jeep liberty check engine light on
Jeeps in general are alergic for Bosch O2 sensors:D. Most of the problems occur due to the slower heating of the Bosch sensors compared to the OEM (Denso) sensors.
If you have a scanner which shows live data, you could check the fuel trims, which probably are negative, making the fuel/air mixture too lean and causing misfires and hesitation on acceleration. Just disconnect the upstream sensors for now and testdrive. If the hesitation and misfire is gone, change the upstream sensor with Denso sensors. You will get other codes due to the disconnected O2 sensors, but it has to be reset anyway. Without the O2 sensors connected, there will be no fuel trimming and the PCM regulates in open loop, but then you know that sensors are the culprit.

RUIDOSO JAMES 08-08-2013 04:07 AM

Should I just leave the Bosch downstream sensors alone, or replace them as well.

Frango100 08-08-2013 11:00 AM

Re: 2006 jeep liberty check engine light on
The downstream sensors are not used for fuel injection trimming but only for catalisator performance, so you could leave them as is.
But i would first electrically disconnect both upper sensors (and stow the wiring away from hot exhaust parts) and see if the misfiring is gone before spending more money.

RUIDOSO JAMES 08-08-2013 11:02 AM

I'm on it. I will check the fuel trims this morning and disconnect o2 sensors afterwards. I will let you know what happens.

RUIDOSO JAMES 08-08-2013 08:18 PM

Fuel trims where negative 5 I am disconnecting the o2 sensors tonight so I can see if it keeps misfiring.

RUIDOSO JAMES 08-11-2013 01:21 PM

Ok. I have had the o2 sensors disconnected for several days now, and no more misfires. What I am wondering though is why are the catalytic converters now smelling like sulphur. Is it because the o2 sensors are disconnected, or does it mean something else is wrong?

Frango100 08-11-2013 02:15 PM

Re: 2006 jeep liberty check engine light on
The idea was not to drive for days with the O2 sensors disconnected, just to confirm that the misfire was over.
Not sure about the reason of the smell, but with the O2 sensors disconnected, more fuel is measured then in fact is needed (rich mixture).

RUIDOSO JAMES 08-11-2013 03:09 PM

Sure it didn't damage anything. Only drive about 50 miles total. The densos will be here tomorrow so I have reconnected the o2 sensors until I can switch them out. Thanks for your help thus far. I will let you know if the densos fix the problem.

RUIDOSO JAMES 08-13-2013 10:04 PM

Ok, so I got the denso o2 sensors today and installed them. The jeep ran for about 30 minutes in stop and go traffic, and them the check engine light came on. Not sure what to do from here. I guess it's time to shell out more money to change out the coil packs. Any other ideas? What is a good brand of coil packs?

Frango100 08-13-2013 10:48 PM

Re: 2006 jeep liberty check engine light on
I don't believe that the coil packs are the culprit. Did you check the fault code(s)? How does the engine run, does it feel that it misses or lacks power? Don't know the Liberty, but it most probably will also show the faults doing the key dance: ignition switch off/on three times and leave in on at the third time. The odometer will show DONE, or a fault code(s).

RUIDOSO JAMES 08-13-2013 11:17 PM

Unfortunately The 2006 Liberty won't do the key dance I will check codes again tomorrow at the shop and let you know what they are

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