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Mark, 22 Year Factory trained technician
Category: Jeep
Satisfied Customers: 11332
Experience:  Jeep factory training........25 years in the industry.
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2006 jeep liberty: 3.7l..I have a code p0305 and it misses

Resolved Question:

I have a 2006 jeep liberty with a 3.7l engine in it. I have a code p0305 and it misses sometimes but not all of the time. I replaced the #5 coil and all 6 spark plugs. I drove it a bout 200 miles and the light came back on with the the same p0305. I switched the coils around and nothing changed. I did clean the injectors but maybe injector problem?Need help
Submitted: 6 years ago.
Category: Jeep
Expert:  Mark replied 6 years ago.
Welcome to Just Answer Jeep my name is Mark.

Since you have eliminated the ignition system, your next step is to swap the injector with another cylinder and see if the misfire moves to the new cylinder.

Also, a compression test on that #5 cylinder would be a good thing to do righ tnow so that you know the cylinder is still mechanically sound.
Customer: replied 6 years ago.

Does jeep have problems with injectors?

Expert:  Mark replied 6 years ago.
Not normally, no, but we need to eliminate that possibility.
Customer: replied 6 years ago.
I just checked compression in #5 and #3 and it was 145 to 150psi swaping injectors now
Expert:  Mark replied 6 years ago.
Customer: replied 6 years ago.
I just switch injectors around but I can't get it to miss right know. I have seen a TSB for valve keepers or something like that. Have you heard of any other isues?
Expert:  Mark replied 6 years ago.
Yes, I was just going through the TSB's.

Engine Misfire At Idle
This bulletin involves installing revised intake valve locks and intake valves.
2005 - 2006 (KJ) Liberty/Cherokee (International Markets)
2005 - 2006 (ND) Dakota
NOTE: This bulletin applies to vehicles equipped with a 3.7L engine (sales code
The customer may experience occasional engine misfire at idle (rough idle). The
malfunction indicator lamp may illuminate for single or multiple cylinder misfire.
1. Place vehicle in park or neutral.
2. Using a StarSCAN® or DRBIII®, monitor which cylinder is misfiring. Cylinder # XXXXX is the
most likely cylinder to have idle misfire, a cylinder on the opposite bank very very
rarely may exhibit a misfire at idle.
NOTE: When monitoring which cylinder is misfiring, counts should be above 10 per
3. Record misfire counts for 1 minute.
4. Rev engine up to 3500 to 4000 rpm and release, do not hold engine at elevated rpm
let it come back down to idle.
5. Monitor the cylinder misfire count for one minute. If the misfire rate does NOT reduce
to less than 5 per minute then repeat Step #4 and re-monitor up to ten times.
6. If the misfire rate DOES reduce to less than 5 per minute, perform the Repair
Procedure. If the misfire rate does NOT reduce to less than 5 per minute after
repeating Step #4 ten times this bulletin does not apply and further diagnosis is
NUMBER: 09-007-06
GROUP: Engine
DATE: August 19, 2006
Qty. Part No. Description
12 53022277AA Lock, Valve
AR (6) 53020747AB Valve, Intake
AR (2) 53020989 Gasket, Head
AR (1) 53013932AB Gasket, Exhaust Manifold Right
AR (1) 53013933AB Gasket, Exhaust Manifold Left
1. Use the procedures outlined in TechCONNECT 9-Engine>Cylinder
Head>Intake/Exhaust Valve And Seats>Removal And Installation to replace ALL
intake valves and valve locks of the cylinder head that has the misfiring cylinder. Both
cylinder heads must have the locks replaced.
2. Repeat Step #1 through Step #5 of the Diagnosis monitoring all cylinders for misfire
after the repair work is completed.
3. A cylinder on the opposite bank very very rarely may exhibit a misfire at idle. If the
opposite bank now has a misfire, then the new keepers have allowed a non-rotating
valve with uneven wear to rotate and induce a misfire. In this case the intake valves on
this head must now be replaced.

Customer: replied 6 years ago.
how would I determine if this applies of I don"t have that kind of scan tool?
Expert:  Mark replied 6 years ago.
Without the proper tooling for this you can only do a process of elimination diagnosis. If you eliminate things one by one........ignition system, injector, fuel pressure, compression etc........and find no problem, then the only thing left would be the valves, as outlined in the bulletin.
Customer: replied 6 years ago.
Thank you for all your help
Expert:  Mark replied 6 years ago.
You're very welcome.
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