I have a very early 1993 (VIN ending in 0959) which had a very frustrating tiptronic issue, now thankfully resolved. Because it was unusual, I thought I would share in case anyone has experienced a similar issue. Car has 127,750 kilometres (approx. 79 k miles). A full transmission service was done less than 5 k previous.
The Issue.
It started as a very intermittent fault. The transmission performed OK say 95% of the time.
The fault was first identified when braking going downhill. The trans dropped from forth to third and stayed locked in third. The dash gear indicator showed the gear still in forth. No warning lights were displayed. It did this several times.
The locked transmission was cleared by dropping to second and working up through the gears, or stopping.
Also if held in third tip mode, it would not change up to forth, (in both tip and then flicked across into full auto) unless dropped to second. Then it cleared and the fault may not occur again for some time. No warning lights appeared.
The fault tended to occur when decelerating and or braking. Normally when going down hill, but had occurred on the flat, e.g. slowing for a roundabout.
Diagnosis.
The independent shop I use ran a diagnostic. The only OBD1 fault code was linked to a failing Oxygen sensor. It was replaced and the code did not reoccur. However the transmission fault was still there.
Next my mechanic Chris (shop owner) asked to have the car for a few days. He advised the transmission had a delay and was also harsh in shifting. After consulting a transmission specialist he replaced the transmission pressure valve. That made a significant improvement in shifting, but did not resolve the third gear locking issue. In fact it had the effect of exacerbating the issue, which occurred much more frequently. Very frustrating.
So it was back to the shop. After some thought the Chris decided to check the MAF sensor and connection. It was dirty and impacting the air fuel ratio. After a thorough clean, the car now runs and shifts better than ever. The transmission issue is now resolved. I couldn't be happier with the service and outcome.
The Issue.
It started as a very intermittent fault. The transmission performed OK say 95% of the time.
The fault was first identified when braking going downhill. The trans dropped from forth to third and stayed locked in third. The dash gear indicator showed the gear still in forth. No warning lights were displayed. It did this several times.
The locked transmission was cleared by dropping to second and working up through the gears, or stopping.
Also if held in third tip mode, it would not change up to forth, (in both tip and then flicked across into full auto) unless dropped to second. Then it cleared and the fault may not occur again for some time. No warning lights appeared.
The fault tended to occur when decelerating and or braking. Normally when going down hill, but had occurred on the flat, e.g. slowing for a roundabout.
Diagnosis.
The independent shop I use ran a diagnostic. The only OBD1 fault code was linked to a failing Oxygen sensor. It was replaced and the code did not reoccur. However the transmission fault was still there.
Next my mechanic Chris (shop owner) asked to have the car for a few days. He advised the transmission had a delay and was also harsh in shifting. After consulting a transmission specialist he replaced the transmission pressure valve. That made a significant improvement in shifting, but did not resolve the third gear locking issue. In fact it had the effect of exacerbating the issue, which occurred much more frequently. Very frustrating.
So it was back to the shop. After some thought the Chris decided to check the MAF sensor and connection. It was dirty and impacting the air fuel ratio. After a thorough clean, the car now runs and shifts better than ever. The transmission issue is now resolved. I couldn't be happier with the service and outcome.
