95 Jetta Bucks

We got my son a 1995 Jetta III with the 2.0l engine. The price was
right (USD 1500 under book value), and we knew going in that it was a
bit of a project car. A timing belt, water pump, injector seals, one
new injector, shocks, front brakes and rotors, partial exhaust system,
shift linkage "adjustments," new instrument lights, and assorted nits
and lice later, it's pretty close to roadworthy.

There's one significant problem left. Sometimes (but often), it bucks
under acceleration. Sometimes it does not. The weather and temperature
have no effect; it can be rainy or dry, cold or warm. Cleaning the coil
ground wire helped reduce the frequency significantly. The coil wire
resistance is OK, cap and rotor are new, and no sparks show in the dark.
No check engine light or new codes (since the injector and seals were
replaced, that is).

Any ideas? The coil is about USD 100. I don't mind replacing it if
it's a common Jetta problem, but after the foregoing repairs I'm
reluctant to shell out for it without a bit more evidence...diagnostic
information very welcome!

Also...any other common problems to watch or check for?

Thanks.

JRE

Also post or search in Passatworld.com There is alot of information there.
"JRE" > wrote in message
...
> We got my son a 1995 Jetta III with the 2.0l engine. The price was
> right (USD 1500 under book value), and we knew going in that it was a
> bit of a project car. A timing belt, water pump, injector seals, one
> new injector, shocks, front brakes and rotors, partial exhaust system,
> shift linkage "adjustments," new instrument lights, and assorted nits
> and lice later, it's pretty close to roadworthy.
>
> There's one significant problem left. Sometimes (but often), it bucks
> under acceleration. Sometimes it does not. The weather and temperature
> have no effect; it can be rainy or dry, cold or warm. Cleaning the coil
> ground wire helped reduce the frequency significantly. The coil wire
> resistance is OK, cap and rotor are new, and no sparks show in the dark.
> No check engine light or new codes (since the injector and seals were
> replaced, that is).
>
> Any ideas? The coil is about USD 100. I don't mind replacing it if
> it's a common Jetta problem, but after the foregoing repairs I'm
> reluctant to shell out for it without a bit more evidence...diagnostic
> information very welcome!
>
> Also...any other common problems to watch or check for?
>
> Thanks.
>
> JRE

Try the VWvortex Jetta forum. Lots of experts there.

In rec.autos.makers.vw.watercooled, JRE wrote:
>There's one significant problem left. Sometimes (but often), it bucks
>under acceleration. Sometimes it does not. The weather and temperature
>have no effect; it can be rainy or dry, cold or warm. Cleaning the coil
>ground wire helped reduce the frequency significantly. The coil wire
>resistance is OK, cap and rotor are new, and no sparks show in the dark.

A mist from a water sprayer might help produce sparks in the dark.

> No check engine light or new codes (since the injector and seals were
> replaced, that is).
>
>Any ideas? The coil is about USD 100. I don't mind replacing it if
>it's a common Jetta problem, but after the foregoing repairs I'm
>reluctant to shell out for it without a bit more evidence...diagnostic
>information very welcome!

Can you go at steady high speed without symptom?

Tom's VR6 wrote:

> In rec.autos.makers.vw.watercooled, JRE wrote:
>
>>There's one significant problem left. Sometimes (but often), it bucks
>>under acceleration. Sometimes it does not. The weather and temperature
>>have no effect; it can be rainy or dry, cold or warm. Cleaning the coil
>>ground wire helped reduce the frequency significantly. The coil wire
>>resistance is OK, cap and rotor are new, and no sparks show in the dark.
>
>
> A mist from a water sprayer might help produce sparks in the dark.

If the coil wire were bad enough to cause this, I'd expect to see them
dry, but I can try this.

>
>
>> No check engine light or new codes (since the injector and seals were
>> replaced, that is).
>>
>>Any ideas? The coil is about USD 100. I don't mind replacing it if
>>it's a common Jetta problem, but after the foregoing repairs I'm
>>reluctant to shell out for it without a bit more evidence...diagnostic
>>information very welcome!
>
>
> Can you go at steady high speed without symptom?

Yes, when it's not failing. No, when it is. You can feel the miss
under load when it's failing; it's perfectly smooth when not.

JRE

In rec.autos.makers.vw.watercooled, JRE wrote:

>
>>
>> Can you go at steady high speed without symptom?
>
>Yes, when it's not failing. No, when it is. You can feel the miss
>under load when it's failing; it's perfectly smooth when not.

I was thinking fuel perhaps. A clogged filter would slow you down
accelerating and at steady high speed. A marginal rear fuel pump
would tend to work a little better with a full tank.

Tom's VR6 wrote:

> In rec.autos.makers.vw.watercooled, JRE wrote:
>
>
>>>Can you go at steady high speed without symptom?
>>
>>Yes, when it's not failing. No, when it is. You can feel the miss
>>under load when it's failing; it's perfectly smooth when not.
>
>
> I was thinking fuel perhaps. A clogged filter would slow you down
> accelerating and at steady high speed. A marginal rear fuel pump
> would tend to work a little better with a full tank.
>

Oh. I thought that too, at first, and bought a filter we wound up
returning after checking the fuel pressure under load. I should have
mentioned that the fuel pressure is high (45 PSI, IIRC) and perfectly
stable when this happens. Also, at full acceleration and high RPM, when
the car's working, it's fine. This happens at any RPM. This seems to
rule out the fuel pump, filter, and regulator.

JRE

COIL. Just had mine replaced for much the same symptoms.