Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing +4 Hesitation

Ever since we have had our +4 from new we have had a slight hesitation on accelerating but have never cured it. I changed to a K&N filter the other week and think it has made it slightly worse. I have the full AR manifold and exhaust and Clubsport tune but that didn’t make any difference. The other week I held my hand over the air inlet and it didn’t make a bit of difference to the engine so guessed it was getting air from somewhere else and then found inside the air filter housing I could see daylight around the outlet pipe so have sealed that up but made no difference. Haven’t had a chance to play anymore as away now so wondered if all you good people had any ideas.

Fitting the less restrictive K & N would weaken the mixture if the adaptive mapping is already on limits of envelope. Not too surprising it's worse therefore.

Yes I feel it could be the mixture is on the weak side but you can’t change it. It does smell the opposite on startup from cold when it smells too rich.

Intentionally I have little to no involvement in vehicle digital systems, but using simple logic in terms of some carb fuelled cars having a pump jet which under a rapid change in throttle position pumps more fuel into the inlet manifold, and which causes me to then wonder the way a similar requirement might be achieved via digital means... I`m guessing the throttle position sensor will play a part and more than likely the air flow monitoring sensor, perhaps engine temp too, even the knock sensors might be looked at and ign timing adjustment... as for what else the map might rely on I have no idea, thus it seems there might be quite a lot in play, any one of which may affect the performance..?

Given you mentioned some sort of issue relating to the lack of suck, wherever you detected that..? Perhaps with a few feet of flexible pipe of a diameter that you can fit close to your ear, the other end of which you can run round the joints and gasket locations around the inlet manifold and throttle body where extraneous air might creep in and upset the fuelling solution as decided by the map, you might just detect something... If you have a servo the pipework feeding it might also have an issue upsetting fuelling..

Just thinking in type.. in the hope it might help in any way, and hopefully not muddy the water..

Which engine? Duratec or GDI?

2019 so must be a GDI.

My GDI passed the MoT today with the slightly modified air intake system and K&N filter. But the Lambda was on the rich side, and the exhaust tailpipes, (which have been clean since having the AR flash) were sooty after Scotland, so I may refit the standard filter and see what happens.

I may also meddle a bit more by removing the long ducting pipe and see if I can get the air in through the side louvres..........

Yes Dave your last article in Miscellany was good timing and look forward to the next instalment. I too was going to try and remove the long ducting pipe when we get back from holiday and also check the air temperature of the air intake when this was removed.
Our exhaust has always been spotless and normally average about 43 mpg. As the K&N lets more air in I would have thought it would have been on the lean side.

Ditto unless the K & N was too small for the job.

It's in the standard can, which may be the problem.