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Master Auto Tech.
Master Auto Tech., master tech.
Category: Dodge
Satisfied Customers: 610
Experience:  A.S.E. Master technician. Over 20 years working on import & domestic. Owner/operator of an auto shop
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P0300 code set. Multi-cylinder misfire. Replaced plugs with

Customer Question

P0300 code set. Multi-cylinder misfire. Replaced plugs with no change. It is the 3.5 cylinder and very rough idles and stumbles at all levels of acceleration. Any ideas?
JA: Sometimes changing spark plugs can be a challenge -- more than a few things to consider. Fortunately, the mechanics we work with have tons of experience dealing with them. Tell me a bit more about what's going on so he can help you best.
Customer: Took it to an independent mechanic and he diagnosed a bent lifter but I am hesitant to believe it because there is no specific cylinder code just the P0300. This occurred once before for about 5 minutes but disappeared. That was approximately 30 days ago.
JA: Are you hoping to fix this yourself?
Customer: I am or at least find a mechanic I can trust to do it for me at a reasonable cost. The first mechanic quoted $2,300.00 and I think maybe he is not being straight with me. Finding a good mechanic locally is a real challenge.
JA: Is there anything else important you think the Dodge Mechanic should know about your Dodge?
Customer: It has 145K on it with routine maintenance accomplished through the dealership. I would return it to them but they are booked for over 2 weeks to just look at it.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Dodge Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Dodge
Expert:  Master Auto Tech. replied 1 year ago.
Hi, I'm sorry you are having trouble with your dodge. I will try to help.
I'm a full time mechanic and have been a mechanic for over 20 yrs and I work part-time here on JustAnswer to help you and others repair their own vehicles, and I get credited by your ratings.. So before leaving the site make sure and leave me a rating. You can still reply to me as many times as neeed, even after the rating.. I will need for you to be my hands and eyes since I'm not there.First, so I can be of more assistance, can I ask what yr, model and engine size is your dodge?Thanks
Customer: replied 1 year ago.
2007 Dodge Charger, 3.5 liter. About 145K mileage. Dealer serviced usually. Code reader says P0300 and the vehicle very rough idles and stumbles and shakes at all levels of acceleration. Stalls 50% of the time at a stop for signal or corner. Has new proper plugs installed after the problem began without resolution. Swapped COP's to different cylinders with no change at all.
Customer: replied 1 year ago.
Originally started rather suddenly while accelerating at approximately 40mph to highway speed.
Customer: replied 1 year ago.
Removing intake cover this is what I see. The enlarged photo is the breather tube at the rear of the cover.
Customer: replied 1 year ago.
Here is the overall view
Expert:  Master Auto Tech. replied 1 year ago.
Looking now. Give me a min
Expert:  Master Auto Tech. replied 1 year ago.
So the first pic is the egr tube. Unfortunately it won't cause a dead miss esp. At off idle and higher rpms. Have you had a chance to do a compression test on all cyl? If so can you list the cyl and pressure of each?Thanks
Customer: replied 1 year ago.
I have not done that yet but will get on it and report back on the results. I had an independent shop take a look and they said they believed a bent valve. I was hesitant to believe them as the misfire leaves for a minute or so and then returns. Seems to me a bent valve remains bent and the problem wouldn't come and go.
Expert:  Master Auto Tech. replied 1 year ago.
Usually that is correct. When does it leave? High rpm? Low? Randomly?Thanks
Customer: replied 1 year ago.
Expert:  Master Auto Tech. replied 1 year ago.
Gotcha. Ya lets first get the results of the compression test. And on cyl 3 & 5 test them first, the retest again at end of the other cyl and see if compression changes drastically or not. Just eliminating possibilities is why.Thanks
Expert:  Master Auto Tech. replied 1 year ago.
Were you able to get the compression test done? let me know so I can assist further. Thanks Sonny