5.7 HEMI Misfire at Idle: Checks Before Buying Lifters

A 5.7 HEMI misfire at idle means the engine needs a diagnosis that considers ignition, fueling, air control, and mechanical condition. A cylinder-misfire code does not confirm a failed lifter. Before approving a camshaft or lifter repair, ask which tests identify the affected component and whether simpler explanations have been assessed.

This is especially useful if the truck still runs poorly after spark plugs or a coil were replaced.

Keep the original diagnostic information

Bring the complete scan report when available, rather than only a remembered code description. Include the conditions when the fault occurred and any earlier repair invoices. Ask whether the shop can document the current findings before information is cleared.

Explain whether the misfire occurs only at idle, after a cold start, or during other normal driving conditions. A symptom described as “always” may actually depend on temperature or time since startup. Those details can change the next test.

If you only feel a vibration and have no documented misfire, begin with the rough-idle and no-code guide. Confirming the complaint is part of the diagnosis.

What a misfire code can and cannot tell you

A code can direct attention to a cylinder or a broader pattern. It does not provide a complete cause, a parts list, or an explanation of why a previous repair failed. The technician must interpret it with current tests and the vehicle's service information.

Ask for the exact code and any related findings. Do not use a generic search result to choose a cylinder location or installation procedure; those details should come from the information for the exact engine.

Distinguish a warning light that is steady from one flashing while the engine runs. Mopar's malfunction-indicator guidance explains the urgency of a flashing light. Do not keep reproducing a severe running fault to collect more examples.

Why replacing one ignition part may not finish the diagnosis

An ignition system needs to be assessed as a system. NGK's ignition-coil technical information cautions against considering a coil in isolation from the boot and spark plug. A new part on the invoice therefore does not establish that every ignition possibility has been excluded.

Ask whether the prior part was confirmed faulty and whether the original complaint changed afterward. The answer helps distinguish an incomplete diagnosis from a separate issue. It also prevents the parts list from expanding simply because one attempted repair did not resolve the symptom.

Correct application and installation matter as well. Provide the previous part numbers and work order to the technician rather than assuming a newly installed component must be suitable.

Fuel, air, and mechanical checks

Depending on the evidence, a shop may investigate injector operation, connections, intake leaks, and cylinder mechanical condition. It should follow a test sequence appropriate to the vehicle, rather than replace each possible component in turn.

Ask which result justifies the next step. For example, a mechanical inspection should follow a reason to investigate mechanical operation, with the shop explaining what the relevant measurements show and what they leave uncertain.

There is no single owner-visible symptom that closes this process. A rough idle with a tick may increase concern, but the HEMI ticking-noise guide shows why the noise still needs to be located.

Check whether vehicle-specific service information applies

For certain 2020 DT Ram 1500 applications, FCA published a PCM-update bulletin covering listed cold-start rough-idle and misfire conditions. The 18-062-20 Rev. A bulletin has specific application details. Ask a qualified shop to check eligibility and current service information.

A bulletin match remains a service-information check, not proof that software caused every misfire. Equally, the existence of a misfire does not prove that an internal kit is needed. The diagnosis should explain which findings apply to this particular truck.

When a lifter or camshaft repair becomes justified

If the tests identify abnormal valve operation or inspection confirms wear, ask for the affected component and the condition of its related parts. The lifter-failure symptom guide provides the broader context for that repair discussion.

Request a written scope before ordering. It should distinguish a lifter-only parts requirement from camshaft damage, additional internal wear, or required contamination assessment. The final list may depend on inspection after access is gained.

For a truck used every day, clarify this point before arranging the repair schedule. Ordering an unverified kit in advance can leave the truck waiting for missing or different parts.

Select the package with the installer

Once the internal repair is confirmed, compare camshaft and valvetrain repair packages using the exact engine requirements. Confirm year, model, engine identification, MDS status, applicable VVT details, and any changes from factory specification.

Read the supplied quantities and exclusions. Do not assume that a cam-and-lifter package includes all required gaskets, fasteners, fluids, or timing parts. Ask the installer to identify any separate items before the order is placed.

The useful selling point of a suitable kit is that its documented contents support the approved job. A kit cannot diagnose a misfire or guarantee that an unrelated running issue will disappear.

Review progress after each diagnostic stage

For a recurring fault, ask the shop to distinguish an observed improvement from a verified resolution. An engine that runs smoothly briefly in the service bay may not have been checked under the condition that originally produced the complaint. Share the cold-start or warm-idle history again when arranging collection.

If more testing is recommended, request the question that test is intended to answer. This keeps the work understandable and gives you a better basis for approving the next stage. A useful repair record explains why a component was selected, rather than listing a sequence of parts tried without a documented result.

Frequently asked questions

The misfire remained after new plugs. Are the lifters next?

Further testing is the next step. The result of one repair does not establish the next failed component.

Does a cylinder-specific code prove mechanical damage?

No. It helps locate the problem being detected. The cause still needs testing.

Should I clear the code before going to the shop?

Preserve the information and describe what happened. Let the technician decide when clearing it is appropriate during diagnosis and verification.

What should a completed repair report include?

It should identify the cause found, work performed, and checks used to verify the original complaint. Keep any remaining concerns clearly separated from the resolved fault.