Fuel too lean?

  • 2.0L
  • 4 CYL
  • 2WD
  • 165,000 MILES
Hi, I have an MK6 2014 Volkswagen Jetta Sedan 2.0 liter (non-Turbo) with engine sales code CBPA. I have had the car for somewhere around 4 and 1/2 years with absolutely no major issues except for the normal wear and tear items and routine maintenance. I've always changed the oil and filter on time, I kind of waited a bit longer than the spec guidance for the spark plug change and I've changed them twice since. It has been an awesome car for all that time until the end of summer.

•It first started as what I believe to be a fuel delivery issue. I couldn't always hear the fuel pump priming and have read on some forums that in some cars you won't be able to hear them. I verified good pressure from the fuel rail. I ended up just looking at the tach when I'm turning it over to see if it moved thus telling me that the fuel pump is working.

• I then bought a scan tool and found DTC code P0444 evap system purge control valve solenoid circuit open. I bought one from the parts store and they both looked the same. During the removal, I noticed that most of the rubber hoses were dry-rotted or on their way.

Volkswagen has some stupid clips that I had to tear off to get them separated from the purge valve.
> The curved and formed hose that is on the left (arrow going towards the driver's side) was damaged during the removal, so I had to go with a non-formed replacement hose. I wasn't even sure if I had the right size.

> The first replacement purge solenoid was garbage and it still failed.
I continued driving it for a few more months and, In between the last failure and the purchase of a new one and its associated hoses from the dealership I got a new code P2402 Evaporative emission system leak detection pump circuit high.

>The car would intermittently have starting issues sometimes stalling out while driving. I found out one day while under the hood that if I wiggled the plug wire boots on the ignition coil along with several sensors and it would start up again.

• It turned out that I had a bad ignition coil and has since then been replaced with a new one. The car ran great for about a month or so and now I've got some new codes associated with the leak detection circuit.
> I've got a cylinder #3 misfire and a DTC for code PO420 catalyst system efficiency below threshold bank 1. And for DTC Code P2096 post catalyst fuel trim to lean bank 1.

> Here are the fuel trim numbers I got from live data. The throttle body was removed and cleaned, as well as the MAF and MAP sensors. The only one that's been tested was the MAF sensor by unplugging it and seeing if the engine stalled.

• I'm pretty sure I've got a vacuum leak on the passenger side somewhere in between the manifold and coolant pump and or an exhaust leak because I can smell the exhaust fumes in the cabin.

• LGSO2FT1(%) -2.3
• SHRT12(%) 93.2
• EVAP PCT (%) 0.4
• O2SLOC B1S12 & B2S----
> O2 System Voltage 0.645 v
• SHRTFT1 (%) 0.0 to -0.8
• LONGFT1 (%) 3.2
• MAP Sensor (kPa) 43.0

I could really use your help in diagnosing this issue so that I don't end up dumping a lot of unnecessary parts, time and money into the car.
Do you
have the same problem?
Thursday, November 24th, 2022 AT 6:15 PM

1 Reply


It does sound like a vacuum leak. Also, if you have an exhaust leak between the engine and catalytic converter, that too can cause a lean mixture.

You indicated the fuel pressure is within specifications. Also, you indicated many of the vacuum hoses are in poor condition. The first thing I would be looking for is a leak. Considering you have emissions codes, that is likely the cause.

Take a look at this link. It explains how to check for engine vacuum leaks. Try this and let me know the results.


Also, pay close attention for an exhaust leak between the exhaust manifold and the converter. The idea you smell exhaust in the vehicle can be dangerous, so until the issue is found and fixed, I would strongly recommend leaving a window open to allow fresh air to enter the vehicle.

Let me know what you find and if you have other questions.

Take care,

Was this
Thursday, November 24th, 2022 AT 8:08 PM

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