AUTO Veteran

The Motorist's Pride

500+
DIY Guides
75K
Community Members
1.2M+
Monthly Views

Interactive Diagrams

More Diagrams
Anti-Roll Bar (Stabilizer Bar)

Anti-Roll Bar (Stabilizer Bar)

A metal bar that connects the left and right wheels of the same axle to reduce body roll during cornering. When one wheel encounters a bump or the vehicle turns, the bar transfers some of the force to the opposite wheel, helping maintain vehicle stability and improving handling characteristics. It can be found on front suspension, rear suspension, or both.

DIY Tutorials

All Tutorials
Explainer

Why Does a Car Shake When Accelerating at a Low R…

A car can shake when accelerating at low RPM due to misfires, worn engine mounts, or fuel and air m…

1 month, 3 weeks ago
3 Mins read
Explainer

Does An Engine Oil Flush Help Or Harm Modern Cars…

Seventy eight percent of major automakers explicitly advise against engine oil flushes on modern ve…

2 weeks, 3 days ago
11 Mins read
Cars

Is the Land Rover Defender 2022 Worth a Trial?

Discover the redesigned Land Rover Defender 2022, a luxurious and capable off-road vehicle. With ad…

1 month, 3 weeks ago
4 Mins read
Aviation and Aerona…

How to Become a Pilot: A Guide for Aspiring Aviat…

Do you dream of flying high in the sky and exploring the world from a different perspective? If so,…

1 month, 3 weeks ago
3 Mins read
Cars

End of an Era: Subaru Legacy Announces Farewell A…

As the sun sets on a legacy that has spanned over three decades, the 2025 Subaru Legacy prepares to…

1 month, 3 weeks ago
3 Mins read
Troubleshooting

What’s That Noise? Diagnosing and Fixing Strange …

“Engine problems account for nearly 30% of roadside breakdowns globally.” That’s a staggering stati…

1 month, 3 weeks ago
8 Mins read
Cars

Kia Recalls Nearly Half a Million Tellurides Due …

Attention Kia Telluride owners! Kia America has issued a major recall impacting 462,869 Tellurides …

1 month, 3 weeks ago
3 Mins read
How To

A Comprehensive Guide to Using Side Mirrors and R…

Ever wondered how you see what's behind and beside you while cruising down the road? The answer lie…

1 month, 3 weeks ago
4 Mins read

Forum Q&A

All Questions

Seeing a barometric pressure reading of 199 kPa on a 2011 Jaguar at ignition-on is a red flag, this value is physically impossible under normal atmospheric conditions.

Ramphele DL
Replies (2)

Ramphele DL : At sea level, you’re looking at roughly 100 to 102 kPa, and even at the bottom of the Dead Sea (the lowest point on Earth), it doesn’t exceed 108 kPa. So, 199 kPa suggests either a serious sensor input error or a corruption in the ECU’s interpretation of the signal. On Jags of this era, the ECU performs a barometric pressure snap shot during key on before engine start, using the MAP sensor as the measuring device since there’s no separate BARO sensor. If the intake manifold or MAP port is contaminated, restricted, or sees abnormal pressure (like a stuck open EGR or boost control issue), it can skew this reading.

Ramphele DL : But more commonly, it’s a circuit issue check the 5V reference line to the MAP sensor for voltage spikes or resistance. I’ve seen cases where a failing alternator or poor grounding introduced enough electrical noise to make the ECU think it was under 2x atmospheric pressure. Verify the actual supply voltage at the sensor with the connector plugged in (back-probing), and ensure the ground is solid less than 0.2 ohms to battery negative.

At sea level, you’re looking at roughly 100 to 102 kPa, and even at the bottom of the Dead Sea (the lowest point on Earth), it doesn’t exceed 108 kPa. So, 199 kPa suggests either a serious sensor input error or a corruption in the ECU’s interpretation of the signal. On Jags of this era, the ECU performs a barometric pressure snap shot during key on before engine start, using the MAP sensor as the measuring device since there’s no separate BARO sensor. If the intake manifold or MAP port is contaminated, restricted, or sees abnormal pressure (like a stuck open EGR or boost control issue), it can skew this reading.

Ramphele DL

Yes, a faulty O2 sensor can cause this issue. It helps regulate the air-fuel mixture. If it's not working properly in cold conditions, the engine may run too rich or lean, resulting in rough idling and vibrations.

Jimna Mustafa
Replies (3)

Alvin Knex : If it’s the O2 sensor, why would it only happen when the engine is cold? Wouldn’t it affect performance all the time?

Jimna Mustafa : Good observation! Many O2 sensors only become active once the engine reaches operating temperature. When cold, the engine runs in 'open, loop' mode and ignores the O2 sensor, relying on preset fuel maps. If the sensor is failing, it might only cause issues once it starts influencing the fuel mixture, or if it sends incorrect signals during warm-up.

Alvin Knex : Turns out the upstream O2 sensor was failing. Swapped it out, and the violent shaking is gone. Thanks for pointing me in the right direction!

If it’s the O2 sensor, why would it only happen when the engine is cold? Wouldn’t it affect performance all the time?

Alvin Knex