Limited to 60mph
QMy 2009 SEAT Ibiza Mk4/5 1.2 BZG runs fairly well on town roads but not on motorways, where it’s slow to accelerate and won’t exceed 60mph and 3000rpm. Over the past few weeks I’ve replaced the MAP sensor, one of the coils and a Lambda sensor, all of which were highlighted by fault codes. Subsequently, the car is running better, but there are still problems with motorway driving.
I manage to cleared all of the fault codes, with the exception of one that was triggered on engine load when motorway driving at 60mph and 3100rpm in fifth gear. The engine lost power and the MIL lamp flashed intermittently. I drove onto the hard shoulder turned the ignition off and on again, after which the MIL lamp went off and car drove ‘normally’ again. The ECU codes indicated ‘16685 Cylinder 1 misfire ‘, which was cleared.
The car drove as normal for the following week, barring one cold morning when it drove poorly for the first mile or so, struggling to drive over a small humpback bridge. Later in the day, the car appeared to drive better, leading me to wonder if the cold start was the issue. The following day, it was not running correctly, with a small misfire at idle without the need for additional acceleration. The following codes were stored: ‘16685 Cylinder 1 misfire’, ‘16556 Fuel trim system too rich bank 1’, ‘17549 Load calculation cross check implausible’ and ‘16556 Fuel trim system too rich bank 1’.
I cleared the codes and took the car on a 15-mile round trip interrogating the ECU and replacing coil for cylinder 1 during the trip, the results were as follows: Drove the car for four miles; drive was not as good as previous week. ECU interrogated and the fault code ‘17549 Load calculation cross check implausible’ was stored. ECU cleared. Drove the car for three miles. Found the code ‘17549 Load calculation cross check implausible’ and cleared the ECU. Fitted another coil in cylinder 1 and drove for four miles and the same code was flagged. ECU cleared. Drove the car hard for three miles (ie, 3100rpm in second or third gear up a hill) and it lost power and the MIL lamp began to flash. After restarting, the MIL lamp went out. Drove a further mile and the code ‘16685 Cylinder 1 misfire’ reappeared. I have read elsewhere that Ibiza owners have had problems with the ignition module and that you can check them using resistance testing. However, I’m not sure that there is such a module on my model because I can’t find any for sale at motor factors or on ebay.
AYour SEAT engine does not have a separate ignition module, but instead uses coil packs which incorporate the coil unit and amplifier internally. These are triggered via the ECU from information received from the sensors.
Reading of your experience, I can see no mention of the spark plugs being replaced. In the past, I have come across a faulty spark plug causing the failure of a new coil pack, so it may be worth changing them. Another trick I use it to swap the coil packs around, taking note of where the pack that was flagged as faulty is placed. If the reported misfire moves with the coil pack, this proves the pack is at fault. If the misfire remains on the same cylinder, then other factors will need to be investigated.
Starting with the basics, I always carry out a compression test to ensure no underlying mechanical issue is present. After swapping over the coil packs, if the misfire has not moved, then the circuit to the coil pack should be checked. From the data I have, the feed from the ECU to ignition coil number 1 comes from pin 57; this should be checked using a continuity meter.
Another possibility is that the misfire is not an ignition problem, but caused by the fuel injection system. Check the connector to cylinder number 1 and swap the injectors around to see if the misfire moves with the injector. This is not as simple as moving the ignition coils but may prove helpful in highlighting the problem.
Finally, Autodata notes that there was a common problem with the Ibiza fitted with the BZG engine involving poor performance. This was due to a bad connection between the accelerator pedal position sensor and harness multi-plug. This may be worth checking, but is unlikely to result in the misfire you are encountering.