Bad gas? Bad plugs/wires?

3.4L • AUTOMATIC
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KHART038
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When cranking up after it’s been sitting, say overnight, it sputters like it’s not firing on all plugs or wires. It will continue to do this until, although it may not be related at all, it gets warmed up/been driven for a few mins. When it’s sputtering, heavier acceleration only makes it sputter more while letting completely off the accelerator at that point, kills the sputtering. It’s only started about a week ago. Again, although it may not at all be related, it’s been running warmer than usual. I’ve flushed the radiator, noticed some leaks and bought Stop Leak. Since putting the Stop Leak in it, it’s definitely stopped most of, or nearly all of the leaks I’d seen before but the engine is still running a good bit warmer than usual. I keep a check on the reservoir but it hasn’t lost or used any water whatsoever yet every time I leave to go somewhere, I’m having to fill up the radiator itself. MOST of the time, just staying moving will keep temp at manageable temp but not all the time and the heater will also help from time to time, though not every time.
Sep 9, 2026 at 3:18 PM

What to check next

Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.

Address the coolant loss before continuing to drive. Let the engine cool completely and arrange inspection rather than relying on repeated top-ups or the heater to control temperature. Ask for a cooling-system and cap test, including inspection of external leaks and the reservoir recovery hose and connections. Tell the technician that the radiator becomes low while the reservoir level stays unchanged, and that stop-leak was added. Repair the demonstrated leak or recovery fault and verify proper filling and bleeding. Also record the trouble codes and investigate the cold rough-running condition. If external checks do not explain the coolant loss, test for internal leakage before deciding on an intake or head-gasket repair. The two symptoms may be related, but that needs evidence. Finding where the coolant goes provides a practical starting point.

Guidance references and applicability

HELLA: Cooling-system check https://www.hella.com/techworld/ae/technical/car-cooling-system/cooling-system-check/ General reference for coolant level, leakage, temperature and component checks. OTC: Compression and cylinder-leakage testing https://www.otctools.com/sites/default/files/2007_930_otc_compression_testers_ada_0.pdf Explains possible cylinder-leakage paths. It does not diagnose a gasket failure in this vehicle.

Read the replies · Discussion summary and reported outcome

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STRAILER
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Do you have a check engine light on? I would run the codes to see which ones are stored, this video can help.

https://www.youtube.com/watch?v=LBCpCWEFnTg

Do not continue driving it while the radiator is losing coolant or running hot. The stop-leak may temporarily slow an external leak, but it can also restrict the radiator or heater core and will not reliably repair an intake-gasket or head-gasket failure.

Please go over this guide as well.

https://2carpros.com/articles/recognizing-the-symptoms-understanding-a-blown-head-gasket-in-your-vehicle/


Sep 10, 2026 at 9:17 AM
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KHART038
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Yessir, the engine light is on but to be honest, it’s been on since we’ve had it and that’s been well over a few years. It only just started this issue roughly 3 weeks to a month ago.
Sep 10, 2026 at 9:40 AM
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STRAILER
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Yep, I would run the codes to see what they are this will help us fix it. In the meantime please go over this guide:

https://2carpros.com/articles/engine-misfires-or-runs-rough/

Sep 11, 2026 at 7:38 AM
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KHART038
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Thank you sir
Sep 12, 2026 at 1:48 AM
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STRAILER
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You are welcome, have a good weekend.
Sep 12, 2026 at 9:05 AM

Discussion summary

Bad gas? Bad plugs/wires?

The owner described rough running after sitting, worse under acceleration, together with higher engine temperature and repeated radiator refilling. Stop-leak reduced some visible leakage, but the reservoir level reportedly stayed unchanged while the radiator lost coolant. The check-engine light had been on for years. Contributors requested codes and discussed possible cooling-system and gasket faults.

Reported outcome: No diagnostic codes, pressure-test results or completed repair were reported.

A head-gasket or intake-gasket failure was not established. The longstanding warning light does not identify the cause of the newer rough-running symptom.

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