mpwdhc
11th March 2018, 05:06 PM
hi guys,
i recently purchased a thor 4.6, which had suffered a head gasket failure (loose bolts, compression leakage under the exhaust manifold). the car came to me with the right head off.
i rebuilt both heads and replaced the cam/lifters.
during cam break in, it was clear it wasn't running happily - missfires, flat spots which come and go, etc.
i put it on a code reader which returned -
* catalyst damaging missfire multiple cylinders
* catalyst damaging missfire cyl 7
* missfire with low/empty fuel
* lambda sensor upstream bank 1
* lambda sensor upstream bank 2
* emission relevant missfire multiple cylinders
* emission relevant missfire cyl 5
i cleared the codes and reset the adaptations. for about 20km the thing drove amazingly, then deteriorated again.
as an experiment i fitted a MAF from a similar vintage mercedes, which gave a good idle but flat performance. figured the latter was down to calibration and that a new MAF would sort it.
ordered a bosch 4.0 MAF from ebay, thinking 4.0 and 4.6 was the same. the inserts had the same part number so i swapped over the housings.
with the new MAF the car runs as it did from the beginning. sometimes it will clear its lungs and start to pull, but a far cry compared to how it was after i reset the adaptations. seems unlikely both MAFs are faulty, but then again, it ran quite consistently with the mercedes sensor.
temp gauge reads at the end of the blue, but diagnostic had it idling at approx 90C. does a code reader base that on the gauge side of the sensor, or EFI? which is to say, could it be a faulty temp sensor?
i feel it runs slightly better on LPG, which to my mind rules out ignition.
any thoughts appreciated. i was certain the new maf would sort it. that magic 20km after resetting adaptations must return!!
i recently purchased a thor 4.6, which had suffered a head gasket failure (loose bolts, compression leakage under the exhaust manifold). the car came to me with the right head off.
i rebuilt both heads and replaced the cam/lifters.
during cam break in, it was clear it wasn't running happily - missfires, flat spots which come and go, etc.
i put it on a code reader which returned -
* catalyst damaging missfire multiple cylinders
* catalyst damaging missfire cyl 7
* missfire with low/empty fuel
* lambda sensor upstream bank 1
* lambda sensor upstream bank 2
* emission relevant missfire multiple cylinders
* emission relevant missfire cyl 5
i cleared the codes and reset the adaptations. for about 20km the thing drove amazingly, then deteriorated again.
as an experiment i fitted a MAF from a similar vintage mercedes, which gave a good idle but flat performance. figured the latter was down to calibration and that a new MAF would sort it.
ordered a bosch 4.0 MAF from ebay, thinking 4.0 and 4.6 was the same. the inserts had the same part number so i swapped over the housings.
with the new MAF the car runs as it did from the beginning. sometimes it will clear its lungs and start to pull, but a far cry compared to how it was after i reset the adaptations. seems unlikely both MAFs are faulty, but then again, it ran quite consistently with the mercedes sensor.
temp gauge reads at the end of the blue, but diagnostic had it idling at approx 90C. does a code reader base that on the gauge side of the sensor, or EFI? which is to say, could it be a faulty temp sensor?
i feel it runs slightly better on LPG, which to my mind rules out ignition.
any thoughts appreciated. i was certain the new maf would sort it. that magic 20km after resetting adaptations must return!!