Over the last couple of years I have had a problem with my mk 1 ZT, it has a intermitant problem which manifests itself with the car suffering a lack of power and the engine sounding much noiser than normal, the odd thing is that after 2/3 weeks of this it will suddenly improve again, loads of torque, smooth acceleration and bags of power.
The car has been to a x-part MG specialist who have put the car on the T4 (Testbook version 4.Computer Diagnostic System), no fault codes were found, and the injector readings were correct, apparently the only thing they could do was to update the ECU (Engine Control Unit) map to its latest version. I had always thought it was a MAF (Mass Air Flow Sensor) issue but having used both a pierburgh MAF (with the synergy) and a replacement Bosch there was no real improvement, disconnecting the MAF and synergy does not make any differance, the in-tank pump has been replaced and the HP injector pump which failed has also been done, but again no improvement. I have also tried several bottles of injector cleaner. Mileage is 128,000ish
The symptoms are:
Reduced torque below 2000 rpm
Reluctance to pull past 3000rpm
Increased engine noise (sounds harsh and unrefined)
No smoke or anything
Both fuel pumps are working (based on them making a noise)
HP pump is only 3000 miles old
The car still maintains its road speed/engine speed (ie 70mph is always 2200rpm regardless of the problem) which suggests its not a clutch issue.
If anyone has any suggestions about what this could be or can suggest a specialist garage near the south coast I would appriciate it as it has stumped the garage and me.
I posted a simular thread on teh other side a few months ago but never got a reply....