Bentley Brooklands 1993 Model

[Vantage87steve]

Hi I am hoping someone can help, I have a 1993 Bentley Brooklands model, it starts fine always and always drives without any issue until you approach 60 mph when it starts to misfire this continues to approx 75mph then disappears if you floor the accelerator it drives through this with almost no misfire. I have changed the plugs HT Leads inc coil pack connections, coil packs, distributor caps, the distributor belt, rotor arms and still no change, we have done a compression test and all cylinders are ‘as new’ the car has covered 43,000 miles - any ideas suggestions please

Thanks in advance

Steve

[stevieturbo]

Presumably at that age, it is fuel injected, it does have cats, lambda sensors etc etc...

So whilst simply throwing a lot of parts at something is no guarantee those parts are now good, if nothing changed by doing so, hopefully it has also done no harm to help diagnosing the actual problem.

If compression is good on all, you hope ignition is good on all....then you need to be looking into what fueling is like whilst driving.
Ideally a gas analyser for each bank...failing that a wideband on each bank...or hopefully the car does have lambda sensors which you can view via live data, or test manually with a voltmeter to see what is going on when driving.

[GreenV8S]

The fact it goes better with full throttle suggests the ignition is OK and makes me suspect a fueling problem. The registration year is about when the requirements for cats was introduced - does it have cats and lambda sensors?

Does the ECU have a diagnostic interface? If it has cats it probably does, but at that age it might not be OBD2.

[Vantage87steve]

Thanks for your responses, it is fuel
Injected and does have Lambda Sensors - more than that I don’t know but will ask my engineer and revert to you. Thanks Steve