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08 Dodge Charger R/T 5.7L Hemi


I've owned this car for 2 years now, it originally had 145K on it. It has been great besides this last year. The car had originally started slightly misfiring about a year ago. Never could figure it out but ignored it since it wasn't very obvious and it was my daily. Well, 7 months ago it just threw a cylinder 7 misfire, MDS code and was not drivable at all; I had to get it towed home. Looked through everything I could and came down to the conclusion that the Exhaust valve was leaking..... well more so I removed the head and found that the exhaust valve was leaking after I couldn't pinpoint anything else. Lifters were in good shape so I left them. Got the head machined and cleaned up. Seats were good so I Replaced the rods, springs, and valves. Installed it back together and everything had been good. But throughout the past few months it's had this strange bogging/idle issue around 1100 to 1500 RPMS. If I start the car and let it warm up and go to leave my apartment, I'll be going about 10-15 MPH and itll be steady around 1300 rpms while driving like that. All of a sudden, it will start bogging up and down from 1000 to 1500 RPMS. I can feel the car bouncing back and fourth from it. If I speed up, the issue disappears. Also if I'm driving around 50 mph and the rpm rests around that area, it'll do the same thing so I have to speed up so I don't feel it. What could be the issue? It's been driving me crazy! I have no codes either. Btw the car had 160K when Exhaust Valve went out. The car now has 168k on it.
 

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Since it only happens at a steady throttle it may be the MDS acting up (transition between 8 cyl & 4 cyl mode). Does the same problem occur if you're driving in AutoStick mode (manual shifting of the transmission rather than full auto "D")? MDS is disabled when driving in AutoStick mode.
When were the spark plugs changed last? A 2008 will have the copper core nickel plated electrode spark plugs that should be replaced every 30K miles.
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Discussion Starter · #3 ·
Since it only happens at a steady throttle it may be the MDS acting up (transition between 8 cyl & 4 cyl mode). Does the same problem occur if you're driving in AutoStick mode (manual shifting of the transmission rather than full auto "D")? MDS is disabled when driving in AutoStick mode.
When were the spark plugs changed last? A 2008 will have the copper core nickel plated electrode spark plugs that should be replaced every 30K miles.
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It actually still does it in Manual mode. I replaced the plugs like 4 months ago with Champion Iridium plugs. I've had a few issues with MDS acting up; I've replaced two since I've had the car. The issue is that why would it keep causing it. I've tried the option of holding the two terminals together for a minute or so to try resetting the computer. But nothing fixes it.
 

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The problem could be the Iridium plugs. Check the Owner's Guide for what spark plugs are listed for your car. For 2008, it's probably Champion RE14MCC4 (copper core, nickel electrodes). Electrode gap = 0.045 in. Torque = 13 (± 2) ft. lbs.

The reason I recommend referring to the Owner Guide is because my 2012 also uses copper core nickel electrode spark plugs but they're NGK. Mopar PN 05149177AB (NGK LZFR5C-11).
Electrode gap = 0.043 in. Torque = 18.5 - 22 ft. lbs.

The earlier 5.7L Hemi engines came from the factory with these nickel electrode spark plugs. Owners have replaced them with Iridium & Platinum spark plugs but the results have been mixed. Some said their engine ran fine & others reported having problems. Going back to copper/nickel factory plugs fixed their problems.

If the car idles OK it's probably not a vacuum leak but it's worth checking the torque on the intake manifold bolts & check the MAP sensor (manifold absolute pressure) at the rear of the intake manifold. MAP sensor should be a tight fit (no air leaks) & the electrical connector/wires should be in good condition.
Torque spec for the intake manifold retaining bolts is 9 ft. lbs. Tighten using the sequence shown below ...

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