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Ask Dodgerench Your Own Question
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3404
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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My name is ***** *****. I have a 2007 ram 1500 with the

Customer Question

Customer: My name is ***** *****. I have a 2007 ram 1500 with the hemi. Sam e ordeal. #7 misfires. Alot. engine light is on. Shakes and rumbles till warm. shut it off and restart, smoothes out and runs like a champ. Is this the lifters? I have replaced all the sensors, plugs, coils, and have looked thru the harness for any damaged wiring.
JA: Thanks. Can you give me any more details about your issue?
Customer: It came back with several codes the first few times I have had to deal with this. The last time I went to napa and got the majority of the sensors that could cause the codes and replaced them. It cured the problems for about 200 miles. Then it all started again. I just took the truck for a cold ride for 5 miles. went into the store, came back out, restarted and the shaking and rumbling was gone. ran smooth. Lots of power. This truck has 115000 on the clock and sounds like a misfire or bad coil. but it goes away after it warms up
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Submitted: 1 year ago.
Category: Dodge
Expert:  Dodgerench replied 1 year ago.

Hi, welcome to JustAnswer! This is Ed.

You probably have a mechanical problem. Either it's a bad pin in the MDS lifter that is slipping out, or the lifter base (roller) has lost inner bearing pins. Either way, it's going to affect intake charge and engine compression.

What I'd suggest would be to take a compression test during the moments when the engine is running its worst.

If the problem is with an MDS pin, you will have absolutely ZIP for compression. NADA, nothing. If that number increases later when the engine is running OK, it strongly suggests that the problem is with the multiple displacement system and the intake valve isn't being lifted at all. This sort of thing doesn't seem likely with a worn-out lifter roller, which will constantly change engine compression depending on when the high and low spots of the lifter change.

Worn-out lower lifter rollers tend to follow an almost elliptical path, not following the camshaft profile as they should. At one cycle, they may be on the low part of the roller (which has needle bearings INSIDE the contact roller), allowing decent lift and valve closure. The next cycle the roller may push the lifter fully-up, holding the valve open because the hydraulic portion of the lifter has compensated for lash adjustment. Misfire occurs mostly when the valve can't close and that may vary with engine speed.

Camshafts are being destroyed with fair regularity on Hemi engines these days because of this sort of problem. Be wary of engine compression variances between cylinders for comparison and be prepared to do a full camshaft replacement if you see this sort of situation.