2003 Jetta 1.8T misfires, dead oxygen sensor

Bad mas air flow sensors can absolutely cause misfires by causing the system
to run too lean. It is also likely to cause misfires on all 4 cylinders as
it affects all of them. MAF sensors are pretty common but not for this
issue. I have also seen faulty Coolant Temp sensors cause this issue.
Especially on cold startup first thing in the morning. What color is the
coolant temp sensor in her car??? If its the black sensor I would recommend
replacing it as they are well known to cause many problems & have been
changed to a newer green sensor.

I would also recommend checking all the vacuum/PCV hoses under the front of
the intake manifold as they are prone to oil contamination which causes them
to go soft & split. These cause air leaks which also can cause misfires on
all cylinders until they get bad enough to cause an adaptation code.

Considering you had misfire codes for all 4 cylinders you need to look at
something that affects all the cylinders rather than things like coils that
usually affect on single cylinders.

Hope this helps.

Craig



"Jim Behning" <jimbehning RemoveThis @doesthisblockpork.mindspring.com> wrote in message
news:p0gr449im5avd51o33qgjln0o7nk2e49ed@4ax.com...
> On Mon, 09 Jun 2008 17:29:52 -0500, William Maslin
> <CATmaslin RemoveThis @cvm.msstate.edu> wrote:
>
>>My daughter just had her 53,000 mile 2003 1.8T Jetta repaired (for a
>>number of issues). They said there were codes for misfires in all four
>>cylinders and that the oxygen sensor needed to be replaced (I assume it
>>was the front one). The car has had an issue with trying to stall for
>>maybe 30-60 seconds after startup.
>>
>>If the oxygen sensor was bad, I'm guessing that it was killed by
>>something upstream like whatever is causing the misfires.
>>
>>Anybody got an idea for "most likely" causes of misfires and startup
>>stalling issues in the 1.8T? I'm thinking coils or MAF sensor.
>>
>>By the way, this is not a dealer service department, but it deals
>>primarily with German cars so the techs are probably fairly
>>knowledgeable. However, I suspect they are not as familiar with "most
>>likely" causes as dealer techs are. Unfortunately the local VW dealer
>>service department is predatory and untrustworthy.
>>
>>Thanks,
>>
>>Bill
> Bad MAF is not going to cause misfires says this shade tree mechanic.
> Temic seems to be a prefered coil. Beru least liked.
>
> Bad coils is a rather well known issue with VWs I would have thought
> most cars had been fixed by now.
>
> http://www.theautochannel.com/news/2003/02/04/154251.html
> http://www.mylemon.com/VW_18T.php
> http://forums.vwvortex.com/zerothread?id=1568254
> http://www.gti-vr6.net/library/engine/beware_Beru_coil_packs.html
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

I agree with Craig.
Since you have the 1.8t (1.8-liter turbocharged) engine each spark plug
should have its own coil. Some of the newer engines will have coils that
might pop up off of the plugs creating a misfire. People have devised ways
to secure these coils from popping up.
The Coolant Temperature Sensor can create a rich mixture so that needs to be
checked out. It might not even throw a DTC either.
Someone needs to plug into the computer to see what is happening there.
Guessing can be very costly!!!
Other things could be visually checked such as the color and level of the
engine oil. The color of the spark plug electrodes. Any cracked or loose
vacuum hoses/connections...........etc.

IF the CTS is bad and has not been changed then it could cause the 02 sensor
to go out again! 8^)
Also using the correct spark plugs will help the performance of this
turbocharged engine. BOSCH Plats are NOT the ones, but this is JMHO. I
think the preferred ones for performance will have 3 side electrodes.
--
later,
dave
(One out of many daves)

"Craig" <turboscirocco.RemoveThis@gmail.com> wrote in message
news:7vj3k.2560$Ec.752@read2.cgocable.net...
> Bad mas air flow sensors can absolutely cause misfires by causing the
> system to run too lean. It is also likely to cause misfires on all 4
> cylinders as it affects all of them. MAF sensors are pretty common but not
> for this issue. I have also seen faulty Coolant Temp sensors cause this
> issue. Especially on cold startup first thing in the morning. What color
> is the coolant temp sensor in her car??? If its the black sensor I would
> recommend replacing it as they are well known to cause many problems &
> have been changed to a newer green sensor.
>
> I would also recommend checking all the vacuum/PCV hoses under the front
> of the intake manifold as they are prone to oil contamination which causes
> them to go soft & split. These cause air leaks which also can cause
> misfires on all cylinders until they get bad enough to cause an adaptation
> code.
>
> Considering you had misfire codes for all 4 cylinders you need to look at
> something that affects all the cylinders rather than things like coils
> that usually affect on single cylinders.
>
> Hope this helps.
>
> Craig
>
>
>
> "Jim Behning" <jimbehning.RemoveThis@doesthisblockpork.mindspring.com> wrote in
> message news:p0gr449im5avd51o33qgjln0o7nk2e49ed@4ax.com...
>> On Mon, 09 Jun 2008 17:29:52 -0500, William Maslin
>> <CATmaslin.RemoveThis@cvm.msstate.edu> wrote:
>>
>>>My daughter just had her 53,000 mile 2003 1.8T Jetta repaired (for a
>>>number of issues). They said there were codes for misfires in all four
>>>cylinders and that the oxygen sensor needed to be replaced (I assume it
>>>was the front one). The car has had an issue with trying to stall for
>>>maybe 30-60 seconds after startup.
>>>
>>>If the oxygen sensor was bad, I'm guessing that it was killed by
>>>something upstream like whatever is causing the misfires.
>>>
>>>Anybody got an idea for "most likely" causes of misfires and startup
>>>stalling issues in the 1.8T? I'm thinking coils or MAF sensor.
>>>
>>>By the way, this is not a dealer service department, but it deals
>>>primarily with German cars so the techs are probably fairly
>>>knowledgeable. However, I suspect they are not as familiar with "most
>>>likely" causes as dealer techs are. Unfortunately the local VW dealer
>>>service department is predatory and untrustworthy.
>>>
>>>Thanks,
>>>
>>>Bill
>> Bad MAF is not going to cause misfires says this shade tree mechanic.
>> Temic seems to be a prefered coil. Beru least liked.
>>
>> Bad coils is a rather well known issue with VWs I would have thought
>> most cars had been fixed by now.
>>
>> http://www.theautochannel.com/news/2003/02/04/154251.html
>> http://www.mylemon.com/VW_18T.php
>> http://forums.vwvortex.com/zerothread?id=1568254
>> http://www.gti-vr6.net/library/engine/beware_Beru_coil_packs.html
>
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

VW had a flash for the ECU for misfire faults. The only way to know if the
engine gets it requires a visit to the dealer to check the software version.
VW should pay for the flash if there are misfire faults stored. So the next
time the MIL light comes on and the engine is misssing vist your deaaaaaaler
before the MIL turns off.
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

If I remember correctly that software flash was a TSB & not a recall so if
the car is out of warranty it won't be covered.


"Lost In Space/Woodchuck" <nowayjack.DeleteThis@comcast.net> wrote in message
news:Xa6dnUXwU6pvQ9DVnZ2dnUVZ_rzinZ2d@comcast.com...
> VW had a flash for the ECU for misfire faults. The only way to know if the
> engine gets it requires a visit to the dealer to check the software
> version. VW should pay for the flash if there are misfire faults stored.
> So the next time the MIL light comes on and the engine is misssing vist
> your deaaaaaaler before the MIL turns off.
>
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

In rec.autos.makers.vw.watercooled, William Maslin wrote:

>
>Anybody got an idea for "most likely" causes of misfires and startup
>stalling issues in the 1.8T? I'm thinking coils or MAF sensor.

All of the other posts offer good info. In addition, I would look at
the engine in the *dark* as it is running and look for arcing on
wires or coil. It is an easy cheap diagnosis method, tho it may be
hard to find good darkness this time of year.

If the misfiring is not occurring as you check, you could try
creating a light mist of water to encourage potential arcing.

So I am not saying arcing is the probable cause. I am saying it is
fairly simple to look for.
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

This message is not archived
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

TSB yes, but misfire faults are related to the emission warranty. And since
the ECU is covered for 8yr/80,000 miles so is the flash.


"Craig" <turboscirocco RemoveThis @gmail.com> wrote in message
news:tJl3k.1784$Mc.863@read1.cgocable.net...
> If I remember correctly that software flash was a TSB & not a recall so if
> the car is out of warranty it won't be covered.
>
>
> "Lost In Space/Woodchuck" <nowayjack RemoveThis @comcast.net> wrote in message
> news:Xa6dnUXwU6pvQ9DVnZ2dnUVZ_rzinZ2d@comcast.com...
>> VW had a flash for the ECU for misfire faults. The only way to know if
>> the engine gets it requires a visit to the dealer to check the software
>> version. VW should pay for the flash if there are misfire faults stored.
>> So the next time the MIL light comes on and the engine is misssing vist
>> your deaaaaaaler before the MIL turns off.
>>
>
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

coil over plug coils, thus can't see secondary voltage.

"Tom's VR6" <no DeleteThis @mail.please> wrote in message
news:r2vr44la5simc3n3s2dnoi2ltp87cequmr@4ax.com...
> In rec.autos.makers.vw.watercooled, William Maslin wrote:
>
>>
>>Anybody got an idea for "most likely" causes of misfires and startup
>>stalling issues in the 1.8T? I'm thinking coils or MAF sensor.
>
> All of the other posts offer good info. In addition, I would look at
> the engine in the *dark* as it is running and look for arcing on
> wires or coil. It is an easy cheap diagnosis method, tho it may be
> hard to find good darkness this time of year.
>
> If the misfiring is not occurring as you check, you could try
> creating a light mist of water to encourage potential arcing.
>
> So I am not saying arcing is the probable cause. I am saying it is
> fairly simple to look for.
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

In article <p0gr449im5avd51o33qgjln0o7nk2e49ed DeleteThis @4ax.com>,
Jim Behning <jimbehning DeleteThis @doesthisblockpork.mindspring.com> wrote:

> On Mon, 09 Jun 2008 17:29:52 -0500, William Maslin
> <CATmaslin DeleteThis @cvm.msstate.edu> wrote:
>
> >My daughter just had her 53,000 mile 2003 1.8T Jetta repaired (for a
> >number of issues). They said there were codes for misfires in all four
> >cylinders and that the oxygen sensor needed to be replaced (I assume it
> >was the front one). The car has had an issue with trying to stall for
> >maybe 30-60 seconds after startup.
> >
> >If the oxygen sensor was bad, I'm guessing that it was killed by
> >something upstream like whatever is causing the misfires.
> >
> >Anybody got an idea for "most likely" causes of misfires and startup
> >stalling issues in the 1.8T? I'm thinking coils or MAF sensor.
> >
> >By the way, this is not a dealer service department, but it deals
> >primarily with German cars so the techs are probably fairly
> >knowledgeable. However, I suspect they are not as familiar with "most
> >likely" causes as dealer techs are. Unfortunately the local VW dealer
> >service department is predatory and untrustworthy.
> >
> >Thanks,
> >
> >Bill
> Bad MAF is not going to cause misfires says this shade tree mechanic.
> Temic seems to be a prefered coil. Beru least liked.
>
> Bad coils is a rather well known issue with VWs I would have thought
> most cars had been fixed by now.

You are correct. However, even the improved coils seem to be
troublesome. For example, our 2002 Passat had all four coils replaced
back in 2002 or 2003 when the big coil disaster occurred. However, it
later developed (around 55K miles) subtle misfire problems which
Woodchuck correctly diagnosed as two bad coils and which took four trips
to the dealer before they figured it out.
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

In article <7vj3k.2560$Ec.752@read2.cgocable.net>,
"Craig" <turboscirocco DeleteThis @gmail.com> wrote:

> Bad mas air flow sensors can absolutely cause misfires by causing the system
> to run too lean. It is also likely to cause misfires on all 4 cylinders as
> it affects all of them. MAF sensors are pretty common but not for this
> issue. I have also seen faulty Coolant Temp sensors cause this issue.
> Especially on cold startup first thing in the morning. What color is the
> coolant temp sensor in her car??? If its the black sensor I would recommend
> replacing it as they are well known to cause many problems & have been
> changed to a newer green sensor.
>
> I would also recommend checking all the vacuum/PCV hoses under the front of
> the intake manifold as they are prone to oil contamination which causes them
> to go soft & split. These cause air leaks which also can cause misfires on
> all cylinders until they get bad enough to cause an adaptation code.
>
> Considering you had misfire codes for all 4 cylinders you need to look at
> something that affects all the cylinders rather than things like coils that
> usually affect on single cylinders.
>
> Hope this helps.

Well, in fact the PCV hose is split (the plastic one) and the car has
the temp light off and on for the past couple months. However the temp
gauge was always OK and the coolanat level in the reservoir was OK.
Nevertheless, the tech replaced a coolant sensor. I don't know whether
he replaced the actual engine coolant sensor or the sensor in the
coolant reservoir. Considering that the car is a 2003 I'm assuming it
has the green sensor as our 2002 Passat had the green sensor. But I
don't know for sure.
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

In article <Lxk3k.6860$xZ.423@nlpi070.nbdc.sbc.com>,
"dave AKA vwdoc1" <vwdoc1nospam RemoveThis @pleasehotmail.com> wrote:

> I agree with Craig.
> Since you have the 1.8t (1.8-liter turbocharged) engine each spark plug
> should have its own coil. Some of the newer engines will have coils that
> might pop up off of the plugs creating a misfire. People have devised ways
> to secure these coils from popping up.
> The Coolant Temperature Sensor can create a rich mixture so that needs to be
> checked out. It might not even throw a DTC either.
> Someone needs to plug into the computer to see what is happening there.
> Guessing can be very costly!!!
> Other things could be visually checked such as the color and level of the
> engine oil. The color of the spark plug electrodes. Any cracked or loose
> vacuum hoses/connections...........etc.
>
> IF the CTS is bad and has not been changed then it could cause the 02 sensor
> to go out again! 8^)
> Also using the correct spark plugs will help the performance of this
> turbocharged engine. BOSCH Plats are NOT the ones, but this is JMHO. I
> think the preferred ones for performance will have 3 side electrodes.

The plugs were replaced at 40K at a VW dealer so they should be the
correct plugs. I emailed her to ask which coolant sensor they replaced.
It might have been the reservoir sensor.

BIll
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

In article <Xa6dnUXwU6pvQ9DVnZ2dnUVZ_rzinZ2d.RemoveThis@comcast.com>,
"Lost In Space/Woodchuck" <nowayjack.RemoveThis@comcast.net> wrote:

> VW had a flash for the ECU for misfire faults. The only way to know if the
> engine gets it requires a visit to the dealer to check the software version.
> VW should pay for the flash if there are misfire faults stored. So the next
> time the MIL light comes on and the engine is misssing vist your deaaaaaaler
> before the MIL turns off.

The car always had the official VW service done at the proper intervals
at a VW dealer so I'm pretty sure the ecu was flashed long ago.
Especially since it had cold start problems back when it was new.
Unless you are referring to a more recent flash.

I agree that MIL light problems warrant a visit to a competent VW
mechanic.

Thanks,

Bill
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor 

If it was due to the colant light flashing when cold then they replaced the
coolant resevoir. This is VERY common. You should check the coolant sensor
yourseld. Its on the drivers side of the head in the top of the coolant
flang. That year car could still have the black sensor.

"William Maslin" <CATmaslin RemoveThis @cvm.msstate.edu> wrote in message
news:CATmaslin-98545C.18185012062008@nntp.msstate.edu...
> In article <Lxk3k.6860$xZ.423@nlpi070.nbdc.sbc.com>,
> "dave AKA vwdoc1" <vwdoc1nospam RemoveThis @pleasehotmail.com> wrote:
>
>> I agree with Craig.
>> Since you have the 1.8t (1.8-liter turbocharged) engine each spark plug
>> should have its own coil. Some of the newer engines will have coils that
>> might pop up off of the plugs creating a misfire. People have devised
>> ways
>> to secure these coils from popping up.
>> The Coolant Temperature Sensor can create a rich mixture so that needs to
>> be
>> checked out. It might not even throw a DTC either.
>> Someone needs to plug into the computer to see what is happening there.
>> Guessing can be very costly!!!
>> Other things could be visually checked such as the color and level of the
>> engine oil. The color of the spark plug electrodes. Any cracked or
>> loose
>> vacuum hoses/connections...........etc.
>>
>> IF the CTS is bad and has not been changed then it could cause the 02
>> sensor
>> to go out again! 8^)
>> Also using the correct spark plugs will help the performance of this
>> turbocharged engine. BOSCH Plats are NOT the ones, but this is JMHO. I
>> think the preferred ones for performance will have 3 side electrodes.
>
> The plugs were replaced at 40K at a VW dealer so they should be the
> correct plugs. I emailed her to ask which coolant sensor they replaced.
> It might have been the reservoir sensor.
>
> BIll
 >> Stay informed about: 2003 Jetta 1.8T misfires, dead oxygen sensor