[REPLACEMENT DRAFT] 5.7 HEMI Rough Idle With No Codes: What to Check

A 5.7 HEMI rough idle with no codes can involve combustion, air or fuel control, or vibration transmitted through the vehicle. An unlit check-engine light does not identify the cause or rule out a developing problem. Diagnosis starts by confirming whether engine operation is uneven, when the shaking occurs, and what tests support the next step.

Buying lifters based on a vibration at a stoplight skips several useful checks.

Describe what “rough” means in your truck

Does the engine speed rise and fall, or does the seat shake while the tachometer appears steady? Does the symptom happen only during the first morning start, after a highway drive, or with the air conditioning operating? Tell the shop whether the vehicle is stationary and which gear is selected.

These observations are not a home diagnostic test. They help the technician reproduce the complaint. A passenger describing a vibration from a normal trip can be useful; there is no need to operate controls or make recordings while driving.

Include when the symptom began. A change immediately after service should be reported with the work order, even if the connection is not yet clear. On a used truck, mention whether engine or control-system modifications are known or simply uncertain.

No light and no codes are different statements

The absence of a dashboard light is an observation. A scan result is a separate piece of evidence. Tell the shop whether “no codes” means someone actually scanned the vehicle, which information was checked, and whether anything was recently cleared.

The Ram OBD II description explains that diagnostic information assists service decisions. It should be interpreted with the complaint and testing rather than treated as a complete mechanical inspection.

A repair appointment is still appropriate for a persistent change in operation. Do not wait for a warning light merely to make the symptom seem more legitimate.

Separate engine unevenness from transmitted vibration

A technician should first decide whether combustion is uneven or whether vibration is being transmitted through another component. That distinction affects the inspection path. Replacing engine internals will not address every source of a shake felt through the seat or steering wheel.

Ask the shop to explain how it reached that distinction. If the engine runs consistently during inspection, the mount or driveline assessment may become relevant. If combustion is uneven, the investigation can move toward ignition, fueling, air control, and mechanical condition.

The purpose is to establish a direction before ordering parts. Several possibilities may remain after the first observation, and the report should say which have been tested.

Checks that may come before a valvetrain repair

For an uneven-running engine, the technician may assess ignition components, connections, intake-system leaks, injector operation, and relevant scan information. The exact sequence should follow the vehicle's service procedures and the evidence already found.

Maintenance records can help identify work that is due, but overdue service alone does not prove the cause. Ask whether a recommended replacement is scheduled maintenance, a diagnosed repair, or an optional preventive item. Those are different reasons to spend money.

When an abnormal engine sound is present too, include it in the report and review the guide to 5.7 HEMI ticking noise. Two symptoms occurring together deserve investigation without automatically being assigned to one component.

Cold-start complaints can require a vehicle-specific bulletin check

FCA bulletin 18-062-20 Rev. A addresses PCM updates for specified 2020 DT Ram 1500 vehicles with a listed 5.7L engine configuration. Its conditions include cold-start rough idle or misfire. This is a reason to check applicability, build details, and current service information, rather than assuming the same update applies to every HEMI. Read the FCA PCM-update bulletin.

The bulletin is not a remote diagnosis for your truck. A shop should determine whether it applies and whether other faults need attention. Do not buy a control module or engine kit based solely on recognizing a symptom in a bulletin.

When lifter and camshaft inspection becomes relevant

If testing points to abnormal valve operation or another internal issue, the repair can move toward mechanical inspection. Request the evidence: the affected cylinder, measurement or inspection result, and condition of related components.

The 5.7 HEMI lifter-failure guide explains the difference between possible signs and a confirmed repair need. A rough idle alone does not establish that all lifters or the camshaft need replacement.

For a high-mileage daily driver, ask how the findings affect the whole repair estimate. An inexpensive individual part can still require substantial access work, while a larger kit can contain items the inspection does not call for.

Choosing parts after the cause is established

Use the diagnosis to build a written parts list. An ignition or air-leak repair should follow that list. If valvetrain damage is confirmed, compare the appropriate camshaft repair kits with the installer.

Verify the exact vehicle and engine configuration, including MDS and applicable VVT details. Establish whether the engine still matches its original specification. A factory Non-MDS engine and a modified MDS engine should not be treated as the same application without supporting documentation.

Compare included camshaft, lifters, guides, seals, bolts, and other components line by line. Ask what is excluded and who will supply it. The purchase should make a confirmed repair easier to organize, with no promise that one kit resolves every possible cause of rough idle.

Make the follow-up comparison useful

Before collecting the truck, ask whether the original idle condition was reproduced during verification. If the complaint occurred after a warm commute with the air conditioning operating, mention that context again. An inspection under a different condition may leave an intermittent symptom unresolved.

Keep the repair record and describe any remaining vibration precisely. A change in the severity or timing of the shake is useful information; simply saying the truck still feels wrong is harder to investigate. If the shop found more than one issue, ask which was repaired and what observation would justify returning for the other concern.

Frequently asked questions

Can the engine run poorly without a check-engine light?

Yes. A persistent operating change warrants inspection even when the light is off. Describe the symptom and provide any actual scan results.

Does shaking at a stoplight mean the lifters are worn?

That is one possible repair direction only after testing supports it. Vibration felt in the cabin does not identify an internal engine part.

Should I reset the computer first?

Preserve the diagnostic information for the shop. Clearing information can make an intermittent complaint harder to evaluate.

What should I bring to the appointment?

Bring the maintenance history, recent repair invoices, the conditions that reproduce the shake, and a description of any accompanying noise or warning light.