[apex]

Friends,



Sometimes, not often, in the morning when first starting out the car bucks wildly - starved for fuel?



The car always starts right up. My drive is a slight incline UP and this seems to happen when "gliding" up the hill before turning, with very light application of the gas pedal. Put in the clutch, tap the gas, and the problem goes away.



Can anyone explain this behavior? Recently changed fuel filter, but I believe this behaviour pre-dated that fix.

Partial Post: Please Login or Register to read the full post.

[Greimann]

If it only does it from a cold start and with the throttle closed, as in coasting, I'll bet it has something to do with the idle stabilizer valve. It is either hanging up and needs cleaning, or you have found an unusual operating mode that causes it to do that "wild thang" even though it is operating normally.



Every other operating condition of cold start OK?

Partial Post: Please Login or Register to read the full post.

[apex]

Hi Dave - yes - everything else seems to be OK. I don't know much - HA! nothing! - about the Idle Stabilizer Valve. Can you point me to some references? Does the factory manual cover R&R of this item?

Partial Post: Please Login or Register to read the full post.

[Greimann]

Yes. the service manual covers this somewhere. The ISV is a large cylindrical device just behind the throttle body, under the intake manifold. There is a wire harness connected to it. It can get gunked up and cause hickpus.

Partial Post: Please Login or Register to read the full post.

[rustech]

Assuming the ISV, If it were to buck at partial throttle, I would think it would get enough air through the throttle body, for the DME to back off the fuel, and compensate for the bad ISV. Also, the erratic operation just when cold seems out of character.



It seems like your first guess of "starved for fuel" is accurate to me. Have you ever run out of gas where your car was bucking? Is that what it feels like? Hope you get it figured out.

Partial Post: Please Login or Register to read the full post.

[apex]

Only ran out of gas once - in college - driving a truck - no bucking... just sputter and coast. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



I'll throw this on the pile of spring projects. It is very intermittent and happens under unique circumstances (cold... slight incline... very little throttle). Actually I haven't tested the "cold" part of the symptoms. Its just that the car generally happens to be cold when I leave my house.



Dave that's a nice word: hickpus. Need to remember that. <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[Greimann]

[quote name='apex' date='Apr 2 2005, 03:30 PM']Dave that's a nice word: hickpus. Need to remember that.  <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" />

[right][post="2777"]<{POST_SNAPBACK}>[/post][/right][/quote]



Oops, forgot to use the spell check! At least the forum software nanny didn't think it was a dirty word <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />



That reminds me of a funny circumstance on another board where this guy was trying to explain where the drain cock was on the radiator. The software kept editing out the C word and he had to just say "drain rooster" instead!

Partial Post: Please Login or Register to read the full post.

[Vedder]

The ISV is just below the Throttle Body, is has a blueish plug on it, well in my VW G60, the ISV is quite important since it control Idle , as for compensation for load as AC etc, but also as a boost bypass for the charger, i used to clean it quite regularly with Brake cleaner spray , several times until no more black stuff coming out (let it soak)and then WD-40 onto it for lube,because the ISV can get stuck inside or not open or close properly.

Also it should has an small hole, on one of the sides, for adjustment, you can do it with an allen key(i dont know if this aplly to the 968 ISV).

Partial Post: Please Login or Register to read the full post.

[skip]

[quote name='apex' date='Mar 30 2005, 02:36 PM']Friends,



Sometimes, not often, in the morning when first starting out the car bucks wildly - starved for fuel?



The car always starts right up. My drive is a slight incline UP and this seems to happen when "gliding" up the hill before turning, with very light application of the gas pedal. Put in the clutch, tap the gas, and the problem goes away.



Can anyone explain this behavior? Recently changed fuel filter, but I believe this behaviour pre-dated that fix.

[right][post="2607"]<{POST_SNAPBACK}>[/post][/right][/quote]



Could be ISV but sounds more like TPS. Throttle Position Sensor - it can get a bit sticky, especially when cold. The microswitch in here sends a signal to the DME if the throttle is closed. If throttle is closed and idle speed criteria is not met, DME shuts off injectors until threshold is reached. Blah, blah, blah - roughly means you get a bucking motion whenever you are near the break point of the throttle being closed because the system is fighting amongst itself to stay alive. If it's been more than 60-75k since you replaced one, do it now. If not, maybe just try to adjust it. TPS is located on the side of the throttle - has cables going to it. Little black box whogimagator.



Good Luck!



Skip@Paragon

Partial Post: Please Login or Register to read the full post.

[apex]

Skip - creepin' up over 100K right now - new TPS is a cheap fix or $$?

Partial Post: Please Login or Register to read the full post.

[skip]

[quote name='apex' date='Apr 8 2005, 11:47 AM']Skip - creepin' up over 100K right now - new TPS is a cheap fix or $$?

[right][post="3028"]<{POST_SNAPBACK}>[/post][/right][/quote]



More than a miniskirt, less than a good toilet <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />



Looks like this:



LINK

Partial Post: Please Login or Register to read the full post.

[rustech]

You can get a good toilet for $85? <img src="/forum/images/smilies/968/ohmy.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[fleetwood]

Recently experienced the same Bucking when driving at partial throttle.

Never had that issue before, it just started out of nowhere (and is rather unsettling).

Replaced the Throttle Position Sensor, and problem solved.

One of the easiest and quikest jobs to do, too.



Wouldnt have known to try that without searching the archives here.

You cant own one of these cars without loving this place.

Partial Post: Please Login or Register to read the full post.

[DaveN]

I think Flash and Jay just got tingly all over <img src="/forum/images/smilies/968/biggrin.png" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[flash]

lol - fleetwood - sooner or later you're going to have to make it to an event, so you can meet some of the people that make the site what it is

Partial Post: Please Login or Register to read the full post.

[lbpesq]

Mine has evidenced significant bucking right after a cold start 2 or 3 times over the three years I've owned the car. Each time, I shifted to neutral and took my foot off the gas for a moment, then back into first and the problem went away.

Partial Post: Please Login or Register to read the full post.

[ds968]

[quote name='lbpesq' timestamp='1374518001' post='145976']

Mine has evidenced significant bucking right after a cold start 2 or 3 times over the three years I've owned the car. Each time, I shifted to neutral and took my foot off the gas for a moment, then back into first and the problem went away.

[/quote]





same here, when it sits undriven for at least two or three weeks ( regretfully, that does happen occasionally ) it needs about 30 - 45 seconds and then it returns to a normal smooth idle all by itself.. If try to drive it right away the shaking and hesitation continues in 1st or in 2nd, etc until those 30 seconds or so expire and then all's ok agian. Oddly, this symptom never occurs if either the car is driven or even if just the engine is turned on runs a bit of time, within any given a 14 day spacing. If not, at around the 15th day it starts acting up. Clearly it has artificial intelligence built-in the ECU which is trying to tell me : "- I'm meant to be driven you bozo, not sit in the garage for all this time.." <img src="/forum/images/smilies/968/glare.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.