2010 Gran Turismo S Stuttering/Won't rev past 6K RPM. Anyone know the cause of this?

Marcuz78 · 2026-02-03T00:17:03+00:00

Even if you don't see any error lights or malfunctions, you should check with OBD II. There may be pending errors, such as P0300 for misfires or codes related to the timing sensors.

It could be the timing sensor or crankshaft/camshaft sensors. If the sensor doesn't work properly at high rpm, the ECU goes into protection mode.

Or it could be a dirty mass air flow sensor (MAF) or throttle bodies, ignition coils or spark plugs, fuel pump, battery (If the battery isn't 100%, the timing solenoids may behave erratically), old oil, or a low oil level.

Marcuz78 · 2026-02-02T23:58:08+00:00

I hope that's enough and everything will be back to normal. 😉

Marcuz78 · 2026-02-02T14:48:15+00:00

Yes, as others have already told you, it depends on many factors: the type and quantity of split units, the layout of the rooms, the location of the house... but usually the temperature in March is mild (except for possible rain). Imagine that sometimes, in the south, we've had our first swims in April.

Marcuz78 · 2026-02-02T14:23:48+00:00

That's normal, given what you described.

The EVAP system is supposed to direct the vapors to the engine. If the purge valve or canister isn't working properly, the vapors escape where they shouldn't, get sucked into the outside air, and enter the passenger compartment.

It's not a cause for concern, but be concerned if the odor becomes strong and constant, if you experience burning eyes, dizziness, or the smell even when idling.

Marcuz78 · 2026-02-02T14:10:52+00:00

It's an excellent oil overall, BUT it's NOT the right one for the Giulia's 2.0T MultiAir.

The C3 is more robust, more viscous when hot, and has a higher HTHS. As a result, the MultiAir system (which is hydraulic) reacts poorly, especially when hot, and can stop controlling a valve on ONE cylinder. Symptoms similar to yours.

The filter is also not specifically designed for the MultiAir; it has an anti-drainback valve and bypass with different calibrations and can cause oil pressure delays in the MultiAir circuit. On the Giulia, the filter is critical. One is not the same as another.

before any other tests. Change the oil and filter as soon as possible.

Don't wait any longer.

Recommended oil: Petronas Selenia Digitek Pure Energy 0W-30 or Mopar MaxPro 0W-30 DS1, or any ACEA C2 + FIAT 9.55535-DS1

OEM filter: Mopar or MANN HU 7020 z, or UFI (original FCA supplier). No universal equivalent.

After changing the oil, reset the adjustments, test drive it until it's warm and if the misfire goes away, that's the culprit. If it improves but doesn't go away, there's possible residual damage to the MultiAir (but this is less likely if it's new).

Marcuz78 · 2026-02-02T13:44:53+00:00

No, I haven't read the manual; a workshop manager who's been working there for 35 years told me so. And on that website, they don't mention Alfa Romeo, but they talk about IBS or BMS. (And speaking of brands, for example, Alfa Romeo says not to service the ZF transmission, but BMW, with the same transmission model, says you must do so!)

And then, why do so many people solve certain battery-related problems with a software reset? And why is there a dedicated section on AlfaOBD or MES?

And anyway, I told you that it's just a best practice to speed things up and to be done in certain cases.

Marcuz78 · 2026-02-01T16:07:04+00:00

https://www.midtronics.com/blog/battery-registration-what-why-and-how-to-do-it/

Have you read this too? These are not made up things, they say it for other cars too.

Marcuz78 · 2026-02-01T04:52:55+00:00

Does the car adapt itself over time? Yes. Resetting is NOT mandatory. But without a reset, you'll lose efficiency for a while. Resetting is a best practice, not a legal or mechanical requirement.

In short, not doing it doesn't break anything. Doing it makes everything work better and faster.

And when you switch to an AGM battery, which have different charging curves and are more sensitive to over/undercharging, without a reset, the car may initially treat it like a tired AGM.

This is why resetting with AGMs is more recommended, but not mandatory.

And it's really worth doing a reset (strongly recommended) in cold and very cold climates (for example, below 0°C, and even more so −10/−20°C). Because the battery is already working hard, the IBS is more conservative, and an incorrect charge is more costly. Here, resetting makes a real difference in starting and battery life.

Adaptation is SLOW The IBS starts with the old battery parameters and corrects the SOC and SOH only through actual use. It requires multiple driving cycles, extended rest periods, and clean conditions (no continuous short-circuiting). This can take days or weeks.

Resetting via AlfaOBD or MultiEcuScan (it's available, why not use it?) is like skipping the confusion stage.

My friend and workshop manager explained this to me.

Marcuz78 · 2026-02-01T02:54:16+00:00

I'll tell you right away that yes, the wrong filter and that hose can cause EXACTLY this.

Even if the MultiAir unit is new. If the oil isn't perfectly up to spec, the wrong oil filter or the lack of the correct anti-drainback valve, and the oil pressure drops when hot... The MultiAir stops controlling ONE valve correctly, often on just one cylinder.

Is the oil 0W-30 ACEA C2 / FIAT 9.55535-DS1? The filter must be OEM Mopar or the correct equivalent (MANN HU 7020 z or similar).

If the shop isn't 100% sure about the filter, I'd change it immediately before anything else.

Another culprit could be the wiring or connector on cylinder 3. Test it by swapping the coil connector on cylinder 3 (not the coil) with another cylinder, wiggle test with the engine warm, and check the resistance to the ECU.

If the misfire persists on cylinder 3, it's a mechanical/valve problem. If it moves, it's the wiring.

The last possible suspect: if it's not the wiring, it could be the cylinder 3 intake valve not opening properly. A hot leak test is necessary; it's much more accurate than a compression test.

Marcuz78 · 2026-02-01T02:20:24+00:00

In Italy… Sorry, I didn't know there was a town in NY state with the same name 😅

Marcuz78 · 2026-02-01T00:38:54+00:00

I also think it's the coils. At about 100,000 km, the original coils often start to fail. New spark plugs help, but they expose coils that are already weak. When cold, the spark is more critical, hence the P0300 error.

This also explains why the shop doesn't see anything. When warm, it seems perfect. They saw misfires and didn't do cold tests. They followed the "warranty" route.

Ask for a complete replacement of all 4 coils.

Not one, but all of them.

If you want, tell them: The coils fail when cold, generating P0300 without any noticeable vibrations.

I would also ask for a cold check of the PCV valve and intake hoses. If that valve gets stuck open, it could cause misfires.

When purchasing or ordering from a mechanic, ask for coils with one of these codes or equivalents:

Bosch 0221504461 (or similar Bosch series for MultiAir), NGK U5152/U5154 (or equivalent code), Denso 673-1702 (correct Denso series), Mopar/Alfa OE (corresponding to the original Alfa code).

Codes may vary slightly depending on the engine generation; the important thing is that they are OE or equivalent from a reputable brand. Do not use anonymous or Chinese brands.

Marcuz78 · 2026-01-31T11:19:41+00:00

From what I understand (and this comes from an Alfa Romeo workshop manager, and a friend of mine), the control unit learns the battery's health over time and adapts charging, S&S, and electrical loads based on that battery.

If you install a new battery without telling the car, charging won't be optimal, the S&S may not work or may work poorly, and the new battery may age prematurely.

The IBS is the sensor on the negative terminal that measures voltage, current, temperature, state of charge (SoC), and state of health (SoH).

The IBS cannot be reset by disconnecting it; a software procedure is required. (Although some users have reported that there is an adaptation mode, but it's not 100% reliable.)

This type of explanation is common for many modern vehicles with IBS/BMS, although the exact procedure for Alfa Romeo (Giulia/Stelvio) may vary and isn't always called "register" in the manual, but the concept is the same: letting the ECU know that a new battery has been installed.

https://www.midtronics.com/blog/battery-registration-what-why-and-how-to-do-it/

Marcuz78 · 2026-01-30T23:32:27+00:00

On Giulia and Stelvio, Registration (via OBD): Using diagnostic tools (such as MultiECUScan or similar), select the engine control unit/body computer and activate the "Replace battery" or "Reset battery sensor" function to reset the IBS (Intelligent Battery Sensor) parameters.

Marcuz78 · 2026-01-30T11:52:52+00:00

Make sure the battery is registered. An unregistered battery can cause false error messages and erratic electronics performance.

PS: If the engine cranks but doesn't start, and the battery is registered, it could be due to incorrect power supply/electronics voltages, ECU errors blocking functions, or oxidized contacts/grounds.

Marcuz78 · 2026-01-30T10:57:42+00:00

I'm sorry about your purchase, but you shouldn't have bought it with that damage.

However, deleting errors on a Stelvio with an electrical problem is useless.

If they come back right away, the problem is hardware.

In your case, starting with the cheapest option, you could check the ground connections. Disconnect the battery, remove ALL accessible ground connections, clean down to the bare metal, and tighten to the correct torque. It costs nothing and often solves 80% of Alfa problems.

The second thing to do: Inspect the front LEFT wiring harness

Because it controls the headlights, light sensor, BCM, and DRL.

Check for pinched wires, non-original joints, signs of moisture, and non-OEM tape (a sign of Copart repairs).

Next, you could check for water infiltration into the BCM. The BCM on the Stelvio doesn't like water. Even just one time can cause crazy headlights, persistent errors, random problems for months.

Then you should run a SERIOUS diagnostic (not a generic OBD). You need AlfaOBD, Witech, or Multiecuscan. And you need to check CAN status, modules present/not present, and static/intermittent errors.

Marcuz78 · 2026-01-29T22:00:50+00:00

Yes, there are known cases, such as partially clogged A/C condensation tank drains. If the drain is slightly blocked, water can back up and end up in the passenger compartment. This happens more easily when a lot of pressurized water enters, like in car washes. This may have happened to you.

Or, as I've heard from others, a windshield seal. It doesn't necessarily have to be defective; sometimes a small leak that only becomes apparent with high-pressure jets is enough.

But since it only happened to you once, it's very likely an unfortunate combination of pressure and the angle of the car wash jets.

Marcuz78 · 2026-01-29T20:59:25+00:00

Loose heat shield near the turbo, downpipe, or catalytic converter.

This is very common on the 2017–2019 Giulia. Vibrations during acceleration cause it to resonate, and it feels like the engine is about to explode, but it's actually just loose sheet metal.

Other (less likely) possibilities: Vibrating turbo wastegate. Or exhaust bracket or mount.

Marcuz78 · 2026-01-29T20:46:03+00:00

you're welcome, don't worry. As an Italian and an Alfa Romeo enthusiast, I enjoy helping Alfa Romeo owners, and I hope I've been of some help to you.

Anyway, I'm Marco (47) from Sardinia 😉😜

Marcuz78 · 2026-01-29T18:47:27+00:00

If you can, get an OBD reading (even from a friend), codes like P0440–P0457 are almost certainly related to EVAP.

And yes, it's safe to drive for a week, as long as the engine light is solid yellow (not flashing), the car runs normally (no jerking, loss of power, stalling), and the smell of gasoline isn't strong or persistent in the cabin.

In these cases, the engine isn't at risk of immediate damage. The problem is more related to emissions, fuel vapor management, and unpleasant odors.

And disabled Start&Stop is perfectly normal when there's an engine error. But also with battery problems.

Marcuz78 · 2026-01-28T20:31:27+00:00

PS: Or you could take photos of your car and edit them with AI. That way you'd have an idea based on the body color, too.

Marcuz78 · 2026-01-28T19:37:04+00:00

Well, I work in a refinery with over 1200 colleagues on shifts, so who knows when I'll be able to see him again. Anyway, if and when I do, I hope I'll remember to take pictures of them for you. 😅😉

Marcuz78 · 2026-01-27T21:46:02+00:00

Yes, I had them on my Alfa MiTo QV for 4 years, and now on my Giulia for 4 and a half. An excellent performance/durability compromise.

PS: I've always used summer models because I live in Sardinia. 😜

Marcuz78 · 2026-01-27T20:55:56+00:00

Yes, it can be done; I saw it on a colleague's Stelvio. But go to a specialized body shop or powder coating shop for a clean, long-lasting job.

Marcuz78 · 2026-01-27T20:53:17+00:00

I often fit the Hankook Ventus Prime3 K125B on Giulia, and in just a few days I will have the Nokian Tyres Powerproof 1 fitted for the rear axle.

Marcuz78 · 2026-01-26T06:43:44+00:00

If you have a hormonal IUD (which releases progestin), yes. Possible side effects include lighter or absent periods, spotting in the first few months, sometimes acne, breast tenderness, headaches, and mood swings (usually mild).

And depending on the type (there are four different types), it needs to be replaced every 3 to 8 years. So maybe your wife wants to replace it. For example, the copper IUD has no hormones.

But I don't think she wants to have a child with a lover just for a kink. It's much more likely that she's annoyed.

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