Good Morning,
I've got a 08 Jetta 2.5L CBTA in the shop with a surging idle and a 3,300 rpm idle flare when pushing in the clutch. It had a P0507 code at one time but after running it lately it throws no codes even though the problem occurs every time the engine warms up and it goes into fuel control. I inherited this vehicle from a very reputable shop after they did the following repairs in attempt to rectify the problem. Valve cover diaphragm, throttle body reset, front and rear crank seals, they removed intake and checked for cracks, tested all vacuum ports and hoses, tried a different Throttle body and relearned it. They received this vehicle after customer tried various things himself, so they had to repair the MAF wiring and install a Bosch MAF sensor in place of aftermarket one. Both the first shop and myself have smoke and propane tested for air leaks numerous times.
Here is what I see happening. The vehicle will idle as it's warming up with TPS senor at 12%, engine rpm at 760 to 780 rpm. You can watch the rpm climb to 1800 rpm and the TPS goes to the reset value of 16% ( every throttle reset I've done comes up at 16% and 84%) once 1800 rpm is reached the ECM then shuts off the injectors ( 0.0 pulse width) in attempt to bring the idle down, you can watch the the idle drop as it shuts off the injectors then climb back up as it turns them back on, this cycle is repetitive, causing the surge at idle. I've made half a dozen maps and sent them to Dana and Peter.
Has anyone any ideas?
I've got a 08 Jetta 2.5L CBTA in the shop with a surging idle and a 3,300 rpm idle flare when pushing in the clutch. It had a P0507 code at one time but after running it lately it throws no codes even though the problem occurs every time the engine warms up and it goes into fuel control. I inherited this vehicle from a very reputable shop after they did the following repairs in attempt to rectify the problem. Valve cover diaphragm, throttle body reset, front and rear crank seals, they removed intake and checked for cracks, tested all vacuum ports and hoses, tried a different Throttle body and relearned it. They received this vehicle after customer tried various things himself, so they had to repair the MAF wiring and install a Bosch MAF sensor in place of aftermarket one. Both the first shop and myself have smoke and propane tested for air leaks numerous times.
Here is what I see happening. The vehicle will idle as it's warming up with TPS senor at 12%, engine rpm at 760 to 780 rpm. You can watch the rpm climb to 1800 rpm and the TPS goes to the reset value of 16% ( every throttle reset I've done comes up at 16% and 84%) once 1800 rpm is reached the ECM then shuts off the injectors ( 0.0 pulse width) in attempt to bring the idle down, you can watch the the idle drop as it shuts off the injectors then climb back up as it turns them back on, this cycle is repetitive, causing the surge at idle. I've made half a dozen maps and sent them to Dana and Peter.
Has anyone any ideas?
