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Scott
Scott, Technician
Category: Jeep
Satisfied Customers: 1190
Experience:  Dodge,Chrysler,Jeep Master Tech since 92.ASE Master since 1990.Currently Dealer employed.
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03 JEEP LIBERTY W/3.7 MISFIRE 3 AND 6 CYLINDER AT 2500 RPM

Resolved Question:

03 JEEP LIBERTY W/3.7 MISFIRE 3 AND 6 CYLINDER AT 2500 RPM
Submitted: 7 years ago.
Category: Jeep
Expert:  Scott replied 7 years ago.

Hello, WElcome Ray- Does the engine misfire at idle or just 2500? in gear or park?

Is the misfire detected by the engine computer , or scanner- what scanner? Can it be felt- sorry for all the questions , Scott.

Customer: replied 7 years ago.

check engine light starts flashing scanner shows radom misfires mostly 3 and 6

modus scanner. miss can be felt but then fades at idle test drive does not show only came on when smog check did change plugs and switch coils no change

Expert:  Scott replied 7 years ago.

Ok, We see misfires like this cause by the valves not properly rotating and wearing only in one place- and as soon as the valve moves it stops sealing properly and causes the missfire , There is a service bulletin that relates to this concern - but for 05-06 model years.

Just 2 days ago I diagnosed this concern `on a 03- missfire on 3 , 4 , 5 .

The heads were pulled and liquid poured on the back of the valves leaked past some intake and exhaust valves.

A leak down test could be used . Chrysler has us test this by raising the rpm to 3500 -4000,

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

required. The repair procedure is to remove and replace the intake valves and replace the valve keepers..

 

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