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Dodgerench
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3385
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I have a 09 dodge ram 5.7, i currently have cel cyl 3. What

Customer Question

I have a 09 dodge ram 5.7, i currently have cel for misfire cyl 3. What do u think it can be?
Submitted: 11 months ago.
Category: Dodge
Expert:  Dodgerench replied 11 months ago.

Hi, welcome to JustAnswer!. This is Ed.

Do you actually feel this misfire?

And when does it happen?

Yeah, questions, questions. But it's important for the diagnosis because there are so many flavors of misfire available.

Some may be constant and felt all the time.

Others may be only on a cold or hot engine.

It may be only at idle or under load.

If you can tell me when you feel roughness or loss of power to the exclusion of other times when it's all good, I should be able to help.

Talk shortly,

Ed

Customer: replied 11 months ago.
You feel the misfire after u accelerate quick maybe reach 3000rpm . The engine feels similar to when u unplug a coil plug. After it happens i park n reset the code with bullydog proggrammer . N it goes back to normal . After the truck is warm it wont go on misfire as often. Mechanic told me that it on his scanner it shows that injector from cyl3 shuts off after certain rpm.
Expert:  Dodgerench replied 11 months ago.

Thanks.

Misfire around that engine speed (with the work and exclusions you've already done) make a very unpalatable thing likely.

You may have a flat camshaft.

Roller lifters on the Hemi engines are starting to fail at a rate that's above average. Pin (roller) bearings inside the outer roller bearing surface dissolve or get spit out, causing the lifter to have erratic action. Valves get held open at higher engine speeds, dropping compression and causing this sort of problem.

Have you noticed a clicking noise that gets louder with RPM? Sometimes this happens and when it does, it's a pretty good indication of valve lift issues. I've seen others with flat lifters that never make noise, but if you hear it... it's another nail.

Compression testing of the cylinder -- statically, running (at idle) and under higher speeds-loads -- are the best way to sort out this sort of thing. Cranking compression will likely be good, as will idle (not much demand for lift on these engine speeds) but things will fall apart at around 3K. Compare your 3K reading to another (good) cylinder under identical circumstances to tell what's going on. Compression testers vary so much that I no longer use hard numbers to determine engine health -- I prefer to compare good holes to bad. Using the same tester, differences are more obvious an valid.

Check it out and listen. Let me know if you have any questions or problems and I'll be glad to help. I'm at the shop tomorrow, but will watch for your post.

Ed

Customer: replied 11 months ago.
What can i do to make sure its that before we pull the engine .
Expert:  Dodgerench replied 11 months ago.

Do the running compression test at the speed your misfire occurs on THAT cylinder and another one for comparison. If it's not a mechanical problem, your numbers will vary from the "control" reading.

Differences in compression at cranking speeds -- your normal compression test -- tells you basic things like ring and valve seals. These readings should be very similar between cylinders.

Running (idle) readings are useful for sorting out small valve action variations. Numbers should be within 5% of each other and even that may not be good enough to escape the Misfire Monitor.

Under load or high RPM tests are pretty much the same as what you've already done, but it represents engine breathing at a higher speed. Compare these numbers to a good hole and if lower, chances are good that you have an intake valve that's not lifting. Lower loads (like at idle) have little demand in the valve lift department but it becomes much more important with speed and load.

Expert:  Dodgerench replied 11 months ago.

What did your test show?