DorkusMalorcusTDI
Member
Hi all, I've been searching and finding answers for several months now (unbelievable help/resource) but this one problem continues to elude me. I'm hoping that I haven't just missed the answer, but here's the history/question:
Just acquired a 2000 Jetta w/150K miles a few months ago, it needed some work but was in otherwise good shape. From day one the car did not like cold starts; I would have to crank for several seconds before it finally decided to stay on. And once on there would be a nice cloud of soot for the neighbors to choke on. Once warmed, the engine started fine but car would smoke under acceleration cold or hot. In addition, the idle bobs up and down (900-1200rpm) when stopped in neutral or when coasting to a stop with the car out of gear. However, it will go down to a steady normal idle instantly upon pressing the gas pedal the slightest little bit...and I mean tiny, anything more and the idle will drop to normal for a split second and then the engine will rev up as normal. The bobbing also goes away when I have the AC on. I also notice a shudder at higher speeds, like ~70mph - I can actually see the RPM needle moving back and forth ever so slightly at speed.
I took it to VW dealership and they told me the injection pump was faulty, "a part inside was giving erratic readings, and the whole pump needs to be replaced." I didn't want to believe them just yet, so I found some write ups regarding changing the IQ with Vag-Com and played with that a bit. I found I could settle the bobbing idle by dropping the adaption value to about 32650 (its bottom-most limit), but in doing so increased the IQ to 6-10 at idle. I drove the car this way for the past few weeks, still enjoying hard cold starts, high speed stumbling and less than favorable mileage...but at least my idle was smooth.
This past weekend I installed a timing belt replacement kit. I discovered before removing my timing belt that it was running VERY retarded, basically on the X-axis of the timing graph. I hoped and prayed this was the reason for all of my issues, but alas it didn't fix all of them. After replacing the TB and fuel filter (just in case), and timing it to half-way between the "normal" and "advanced" lines on the graph I can say the car is performing noticeably better and getting better fuel mileage too. The cold start issue seems to have gone away as well, fires right up now. I was so happy I went to the adaption value and returned it to the factory 32768 only to find that the idle was still bobbing, and still can notice the high speed stumbling.
I took another look at the IQ this morning and noticed that it moves around a bit, jumps up and down within a range of 2-4 units. With the adaption value set at its allowable max, I can still only achieve an IQ as low as 5-8 range. Could it be that I just need to do this Quantity Adjuster hammer mod and get the IQ down into the 3-5 range? Is it normal for the IQ to bounce around like it is on mine, or does this suggest that there really is a faulty injection pump problem?
Sorry for the book but can anyone tell me what they think this idle issue may be?
Just acquired a 2000 Jetta w/150K miles a few months ago, it needed some work but was in otherwise good shape. From day one the car did not like cold starts; I would have to crank for several seconds before it finally decided to stay on. And once on there would be a nice cloud of soot for the neighbors to choke on. Once warmed, the engine started fine but car would smoke under acceleration cold or hot. In addition, the idle bobs up and down (900-1200rpm) when stopped in neutral or when coasting to a stop with the car out of gear. However, it will go down to a steady normal idle instantly upon pressing the gas pedal the slightest little bit...and I mean tiny, anything more and the idle will drop to normal for a split second and then the engine will rev up as normal. The bobbing also goes away when I have the AC on. I also notice a shudder at higher speeds, like ~70mph - I can actually see the RPM needle moving back and forth ever so slightly at speed.
I took it to VW dealership and they told me the injection pump was faulty, "a part inside was giving erratic readings, and the whole pump needs to be replaced." I didn't want to believe them just yet, so I found some write ups regarding changing the IQ with Vag-Com and played with that a bit. I found I could settle the bobbing idle by dropping the adaption value to about 32650 (its bottom-most limit), but in doing so increased the IQ to 6-10 at idle. I drove the car this way for the past few weeks, still enjoying hard cold starts, high speed stumbling and less than favorable mileage...but at least my idle was smooth.
This past weekend I installed a timing belt replacement kit. I discovered before removing my timing belt that it was running VERY retarded, basically on the X-axis of the timing graph. I hoped and prayed this was the reason for all of my issues, but alas it didn't fix all of them. After replacing the TB and fuel filter (just in case), and timing it to half-way between the "normal" and "advanced" lines on the graph I can say the car is performing noticeably better and getting better fuel mileage too. The cold start issue seems to have gone away as well, fires right up now. I was so happy I went to the adaption value and returned it to the factory 32768 only to find that the idle was still bobbing, and still can notice the high speed stumbling.
I took another look at the IQ this morning and noticed that it moves around a bit, jumps up and down within a range of 2-4 units. With the adaption value set at its allowable max, I can still only achieve an IQ as low as 5-8 range. Could it be that I just need to do this Quantity Adjuster hammer mod and get the IQ down into the 3-5 range? Is it normal for the IQ to bounce around like it is on mine, or does this suggest that there really is a faulty injection pump problem?
Sorry for the book but can anyone tell me what they think this idle issue may be?
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