Low throttle oscillations

[Powjetta]

When starting out in the morning and evening in first or second with the throttle barely pushed I get the rev/slow fast/slow oscillations that I don't like, as I can see they are hard on engine mounts.  Any ideas as what could be causing this?  I have no idea how many miles are on the IP.  If I push on the pedal or push in the clutch they disappear of course, but is this a symptom of something else?

[jtanguay]

hmmm sounds like low compression to me.  rough idle right?  could be a bad injector, or sticky rings... my old '86 jetta did the same thing, but mainly because of low compression.  once warmed up it idled like a champ

[Powjetta]

No it idles fine, I haven't replaced the injectors at all.  It's just when I'm moving in the parking lot going slow with just a touch on the throttle.  Its like some thing is winding up and then releasing in the injection pump.   The closest other experience is actually pushing and releasing the throttle to max out the suspension travel that I used to do as a young driver and didn't have to replace mounts.  I think it is something in the pump that's wore out that's supposed to help maintain a constant rpm.  Does anyone have a high mileage pump that does this?

[jtanguay]

well from the way you describe, it seems like an acceleration miss.   when you give it a bit of diesel, it starts to idle rough and shake right?  do u have the cold start lever pulled out? that helps immensely!  one thing you might also want to try is a thinner oil, and letting the motor idle for a minute or two before driving off.

how cold is where you are?

[Powjetta]

You don't want to hear about that, I still run the AC at lunch time and going home I'm still watching the temp guage.  It does it when its hot at the end of the trip.  It runs smooth at idle and under throttle.  Its just when moving in second mostly at about 10 - 20 mph with just enough pedal to keep moving along.  My daughter was with me the other day and she says "Dad did you do that"? when it started bucking.

[jtanguay]

thats sounding like a fuel related problem... most likely the injection pump/injectors.  

my money's on the injection pump.  its either going, or needs to be serviced.  (meaning that the a/c idle boost will probably need to be fixed)

[burn_your_money]

Are you at too low of an RPM for the engine?

[jtanguay]

it could be the added load from the a/c being on and not high enough rpm's like burn your money said...

my car does buck in 1st or second if i press the pedal and release it quickly... its almost like an art to keep it from doing it.  i think its normal.  the only car i ever had where it would do it very little, was a big audi 5000. that car was a pig!  my dad had a saturn... and that thing would buck in 1st and 2nd, and in 3rd if the rpm's were low enough  :lol:

[Malacaco]

thats sounding like a fuel related problem... most likely the injection pump/injectors.  

my money's on the injection pump.  its either going, or needs to be serviced.  (meaning that the a/c idle boost will probably need to be fixed)

i don't believe it's the pump. that's the same problem i have with a totally rebuilt pump and my car is still doing that

[Doug]

I have seen the rpm hunt slightly when the timing belt has excessive slack in it.  Check for correct tensioning and bearing condition of the idler on the timing belt. But that would not account for a large rise in engine speed as you say. It must be getting fuel from somewhere.

[Malacaco]

.1probably the problem lies i low compression, because i made a compression test and it acused  low compression in the 1st cylinder. the factory default is about 23:1, the first cylinder had about 16:1, the others were in a 21.5-22 range