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16

There are two possible explanations: If the fuel cap does not form a good enough seal, the fuel injection system may experience problems with drawing fuel from the tank. On newer cars many of them have a fuel cap sensor to detect if the cap is not screwed in. This is related to emissions, although i am uncertain how. I know when I get my yearly emissions ...


9

The EPA regulations require that the fuel tank is a sealed system so that no vapors escape. There is an entire system (Evaporative Purge) dedicated to that task. EPA regulations also require that the ECM (Engine Control Module) check they system for leak. When the right conditions are met IE fuel level between 1/3 and 1/2 tank, outside temp 50 - 90 etc. the ...


7

Though I may not be correct, have you tried opening your hood and using a spray bottle of water on your spark plug wires? Lightly mist around where the wires connect on both ends of the wires, and maybe a few squirts around on the wires themselves. If the vehicle stutters, it may just be that the wires need to be replaced...


6

The CEL trigger implementation will vary across vehicles, but here are a few for you to try out. They should not have any negative effect in the long-term on the vehicle: P010x - unplug MAF sensor P030x - unplug a spark plug wire/coil (unplugging the corresponding injector is recommended) P0420/P0430 - unplug the O2 sensor after the catalytic converter


6

@JPhi1618 answer is good. I would just add a few more, You can unplug the EGR Valve electrical connector, no harm to engine. Pull out a coil pack or coil wire.


6

Start unplugging stuff. The engine will normally run with a lot of the sensors unplugged, but the check engine light will come on quickly. Some easy to reach ones: Mass Air Flow (MAF), Oxygen sensors, sometimes the throttle position indicator (on the throttle body). If you can unplug the power to the secondary air injection pump, it will cause a fun ...


6

It is most likely that this sensor has failed. The question is why does the MIL only come on above 70mph. The answer lies not in the sensor but how and when the sensor is tested by the PCM. Every sensor (and actuator) in the engine control system is tested by the software, but not all the time. Each sensor has its own set of test entry conditions; each OEM ...


5

You didn't mention which engine is in your Jetta, but the Mk IV VWs, especially the VR6 engine, are known to have brittle ignition coil housings that crack and admit water, which leads to misfires. After the engine has run for a while, it burns off this moisture and it starts running fine again. Some VWs were subject to a recall to fix this issue. Based on ...


5

To add to the list, run the engine without the fuel filler cap on.


5

While the fault code that popped the MIL is tremendously useful by itself, freeze frame data offers huge help, as it allows you to see the exact conditions under which the engine decided that there is a fault. You will know at what RPM the code was popped, what the engine load was, whether the engine was warm and in closed loop mode, if it was overheating, ...


4

I haven't been able to find any solid conclusions on the VW forums regarding the root cause for this behavior, but there are some clues as to what could be causing this from the diagnostic code. Fred Wilson's answer remains a distinct possibility but I struggle to reason with why the engine computer would choose to throw a code/MIL for a bad sensor on a ...


4

The P0420 and P0440 are completely unrelated (other than both being related to emissions). The P0420 is having to do with catalyst function. The P0440 having to do with EVAP system. There is no way for one code to have morphed into the other code. P0420 can appear and disappear over time due to the nature of what is being seen by the computer. If the after ...


4

I would find someone else to check out and fix the airbag, while this guy might be great at fixing other things on your car I wouldn't let him touch the airbags. if needed it would deploy Possibly depending on what the code is however it might not. He said that to turn the light off would require removing a few electrical components This ...


3

The diagnostic systems in cars get upgraded every few years. It wasn't until the early 2000's that car manufacturers really started to integrate ways of displaying diagnostic info without an OBD scanner. Typically if it is not included in the shop manual it is not a feature on that car. Your best bet is to go to the local autoparts store or shop and have ...


3

I am assuming that you are in NC based on your profile. You can obtain a wavier if you spend at least $200 I will list the rest of the requirements at the end of this post. I am leery that the catalytic converter is bad, the ECM (the cars computer) uses the post cat O2 sensor to determine cat efficiency and if it's bad as they said it could cause the ...


3

They help us home in on what might be the root cause Maybe an example would help explain why freeze frames are so useful Here is the P0300 freeze frame from that infamous Merc GLK280: +-----------------------------------------+-------------+ | Fuel System 1 status | 1 | | Fuel System 2 status | 1 ...


2

We find FF so useful that we retain it on the customers invoice in case the same code sets later. It is also very helpful when used in conjunction with a test drive on intermittent faults. It tells exactly how to duplicate the conditions under which the fault set. There are times when its limit of setting on only one code is frustrating because it is not ...


2

Because this issue is speed dependent, I'm almost certain that it is related to exhaust gas temperature. Paulster2 suggested checking whether the issue happens at a lower gear. However, then the load on the engine is lower, so there are less exhaust gases. It may be the case that the issue does not happen at a lower gear, therefore. But a good idea to check ...


2

We can still read the code without a code reader with a key dance. Some people said the e-brake must be on in order to do this but the main problem in my case was about the key dance itself. Basically, there's 4 ignition key positions: Off Accessories Run Start When I was doing the key dance, I was doing it between position 1 and 3. However, I just ...


2

DO NOT PAY SOMEONE TO RESET THE BLINKING AIR BAG LIGHT!!!!! Open the driver’s door. Note the rubber covered button located low on the B pillar, a button which is pressed by the door when the door is closed. This is the Driver’s Door Switch (DDS). Turn the ignition from OFF to ON. Press the DDS at least 5 times within 7 seconds after turning the ignition ...


2

First step, I would take the car to a less annoying shop to ask them to read the OBD code - I would assume that there is one to read if the CEL has been on or flashing. Almost any shop will read the code for you at for a nominal / free charge. If you would like to know the information on your own, the code readers are common items on Amazon. I would get ...


2

The first step is to pull the ABS codes. That will give us a starting point for trouble shooting. This model supports flash codes, you will need to jump across terminal A and H of the ALDL connector (under the drivers side of the dash). It may take about 30 seconds before the ABS light starts flashing codes. Count the flashes to get the code, they ...


1

The gas or petrol cap is a good idea. Removing the coil pack(s), on cylinder 1, is another one. Sometimes you can easily find an electrical connector - say the O2 sensor - and disconnect it. This, of course, depends on what connectors are easily reachable. On a Hyundai Coupe, the O2 sensor is easily accessible.


1

The easiest thing I can think of is to remove the gas cap and start the engine. You should quickly see a MIL. The scan tool should report something like Evap emission fault large leak.


1

Bad idle or auxiliary air valve of some sort. Cold-air valve, idle-up solenoid, EGR valve.


1

I had a similar problem on 2 vehicles, a 03 mustang and a 99 bonneville. When the car would come to a stop light the engine would idle too low and stall out. The problem (in both cases) was the mass air flow sensor. Its a piece of electronics that determines the amount of air to let in to the engine from the throttle based on inputs. You could test it by ...


1

You could try changing your fuel filter(s) and PCV valve if your car has one.


1

I have a 2001 Pontiac Sunfire that HAD a similar issue. After having been looked at by far too many people, one mechanic figured out how to recreate the issue by pouring water on a certain part of the engine while running (sorry I'm not sure where exactly), but even that didn't shed much light on the issue since it was supposed to be acceptable to do that. ...


1

I own a 2003 2.0 Jetta which has the same issues. Upon further study and inspection I find that when there is moisture in the air, either raining or dense fog, the car either will be hard to start or will not start at all. When I pop the hood I notice that ALL of the electrical components in the car have condensation on them. For example, even though the ...


1

These two links give some diagnostic information on catalytic converters and O2 sensors: Diagnosing 02 sensor Catalytic converter causing performance problems If the 02 sensor is working properly and thus properly condemning the catalytic converter, one option is to have an exhaust shop replace just the converter. The factory exhaust pipe with the ...



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