Hi all,
02 Audi A3 8L1 1.6L 8V BFQ
I have a juicy one for those who like a diagnostic challenge
I need help finding the root cause of a hesitation noticed in 1st and 2nd gear below 2,000 revs. Also there is a lag in throttle response when coasting in any gear, at any rpm. When I mash the accelerator to the floor I can hear the exhaust rattle as if it was about to stall but it never does, just the annoying delay especially trying to predict when the car decides to engine brake which can be a 1-3 second delay. If I put the car in first gear and leave off the accelerator and let the car drive itself it will accelerate-decelerate-accelerate perpetually, as opposed to driving at a consistent speed on a smooth flat road.
On engine start up the rev counter can be sporadic on occasion (1 in every 8 starts) for the first 0.5-2 seconds before it settles back to normal and stays fine thereafter. I notice that if I rev the car in neutral I can't get it to sit at 2,000 rpm as when I get to 1800 it revs itself up to 2800 or so, wondering if this is related or just a normal condition. Finally there is an intermittent issue with the revs idling high and self oscillating between 1000 to 1800, typical of a vacuum leak but smoke testing confirms repairs up to this point.
Repairs so far:
So, with all of the above replaced and still the issue continues, does anyone have any experience with the above symptoms and can recommend a fix? At this point it looks more like an electrical grounding issue then an (APP sensor) Accelerator Pedal Position sensor. When I replace the cam sensor over the next day or two I will be cleaning all the engine and chassis grounds I can find, while the upper intake manifold is off and I have more room to see things. I have no wiring diagrams for the car if anyone can point me to an appropriate link or whatever for this specific car I would greatly appreciate it. For example, where are each ground wires/straps located? ie. Body grounds (I think there is one under the battery tray), engine grounds, and computer grounds. Without wiring diagrams for example I'm unable to verify looms for resistance or voltage values.
The only electrical testing done so far was today where I checked static resistance between the battery ground terminal and the alternator housing which was found to be 0.3R. The Audi specialist also inspected the o2 sensor loom for faults, none found.
Any help anyone can provide would be greatly appreciated.
02 Audi A3 8L1 1.6L 8V BFQ
I have a juicy one for those who like a diagnostic challenge
I need help finding the root cause of a hesitation noticed in 1st and 2nd gear below 2,000 revs. Also there is a lag in throttle response when coasting in any gear, at any rpm. When I mash the accelerator to the floor I can hear the exhaust rattle as if it was about to stall but it never does, just the annoying delay especially trying to predict when the car decides to engine brake which can be a 1-3 second delay. If I put the car in first gear and leave off the accelerator and let the car drive itself it will accelerate-decelerate-accelerate perpetually, as opposed to driving at a consistent speed on a smooth flat road.
On engine start up the rev counter can be sporadic on occasion (1 in every 8 starts) for the first 0.5-2 seconds before it settles back to normal and stays fine thereafter. I notice that if I rev the car in neutral I can't get it to sit at 2,000 rpm as when I get to 1800 it revs itself up to 2800 or so, wondering if this is related or just a normal condition. Finally there is an intermittent issue with the revs idling high and self oscillating between 1000 to 1800, typical of a vacuum leak but smoke testing confirms repairs up to this point.
Repairs so far:
- Timing belt and water pump changed (as per maintenance schedule)
- MAF sensor cleaned
- Smoke tested and all leaks sealed (Crank case breather found broken, replaced)
- Throttle body replaced (adaption reset by independent Audi specialist)
- o2 sensor replaced (to fix a lean code, confirmed bad, done by independent Audi specialist)
- Fuel pressure regulator replaced (independent Audi specialist)
- Fuel pressure perfect with no drop in pressure over 30+ minutes (leak down test)
- Exhaust gas analysis shows excellent readings (0% CO, 15.8% CO2, 0PPM HC)
- Crank sensor replaced (today, Febi part)
- Cam sensor (will be replaced in the next day or two, Febi part)
- Checking/cleaning all grounds wires
So, with all of the above replaced and still the issue continues, does anyone have any experience with the above symptoms and can recommend a fix? At this point it looks more like an electrical grounding issue then an (APP sensor) Accelerator Pedal Position sensor. When I replace the cam sensor over the next day or two I will be cleaning all the engine and chassis grounds I can find, while the upper intake manifold is off and I have more room to see things. I have no wiring diagrams for the car if anyone can point me to an appropriate link or whatever for this specific car I would greatly appreciate it. For example, where are each ground wires/straps located? ie. Body grounds (I think there is one under the battery tray), engine grounds, and computer grounds. Without wiring diagrams for example I'm unable to verify looms for resistance or voltage values.
The only electrical testing done so far was today where I checked static resistance between the battery ground terminal and the alternator housing which was found to be 0.3R. The Audi specialist also inspected the o2 sensor loom for faults, none found.
Any help anyone can provide would be greatly appreciated.
