Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Musings/observations on 3.7 Roadster throttle body

For some time now I've noticed an intermittent delay between taking my foot off and hearing the exhaust drone from a fully closed throttle. With the vocal side pipes on my Roadster this is very apparent and likely been there since new. It's most certainly not the infamous rev hang issue that early 3.7 Roadsters were plagued with, only manifesting itself as minimal engine braking on gentle run downs and always disappearing when clutch dipped or braking. A secondary but likely associated issue is that idling exhaust note, always a reliable 650 - 670 rpm, can sound louder than normal taking up to 30 seconds to drop to the usual whisper quiet note.

Although only a minor annoyance I decided to investigate after ordering throttle body cleaner. Easy to access I found the throttle butterfly clean looking after 34,000 miles although a few squirts of cleaner removed some muck. Apparently WD40 can also be used for cleaning so squirted a little on throttle spindle by way of mild lubrication. Then asked my partner to operate foot pedal with ignition on engine off. Butterfly swiftly moved to what appeared as fully open position dropping back to fully closed with faint click before opening slightly after split second, when pedal released. This related on OBDII TPS readout showing max 75% with pedal floored to 17.5% foot off. Also noticed was the continuous faint buzz from throttle stepper motor at any held pedal position above idle, expecting it to only run when throttle butterfly was moving.

After exercising butterfly several times re-connected air filter hose and went for 15 mile test drive. Engine started normally dropping back to it's usual idle after throttle blip and maybe 30 seconds. Nothing conclusive here but it seemed that throttle closed position signalled by exhaust note, occurred more swiftly after foot off throttle.

As a side note I had previously bookmarked the website of BBK a company in the USA offering oversize throttle bodies. They claimed an 8 - 12hp increase from their 73mm throttle body conversion, being a straight swap on all 2011 - 2017 3.7 V6 Mustangs factory fitted with 67mm ones and being the full production run with this engine variant. Strange then I measured 73mm on mine, saving a $500+ mistake should I have been tempted

Can anyone explain this?

I can't add anything other than this. When Roadster S3 production was suspended, as MMC were looking to Ford as another replacement engine, I was "interested", and happened to bump into Steve Morris at the factory. Obviously a 3.7 with six speed box was super tempting, although in the end I decided to stick with my S1. The thing was, that Ford were "not interested" other than supplying a (plug in) crated engine, box and instrument set, and there was no deal available on price, which MMC would have liked to negotiate down a bit.

So what Ford supplied in the end would have been a standard set.If BBK is right, then MMC could have changed the throttle body, but being price sensitive, I'm not sure that they would throw another £500 into the mix. So yes, it's a mystery.

Thanks for reply Dave. There is plenty of discussion on the Mustang forums on this issue with BBK offering 85mm upgrades for the Coyote V8 engines and the old 80mm bodies being re-drilled to upgrade 3.7 V6 versions.

Worth remembering the Cyclone V6 was used in a wide variety of other vehicles including Lincoln's, F150 trucks and, dare I suggest, Transit vans . This then begs the question which model engine variant the composite inlet manifold was borrowed from (certainly not Mustang) and, given little interest from Ford, how MMC ended with their logo moulded into same

PM sent Richard

From memory, it was the Transit version fitted to Roadster 3.7. Can't remember where that snippet came from though.

Thanks Graham. Have heard similar but all the engine variants I've seen have throttle body inlet at front of engine including the transverse mounted Transit. It seems likely the main inlet manifold design on Roadster is unique to MMC therefore in positioning inlet at back of engine as well as having Morgan logo moulded in of course.

Richard, I think that perhaps you throttle buterfly was just hanging up a little and allowing air to pass hence the slight level of rev hang. yYour clean up obviousely did the trick though! I remember being told that the plastic bodied throttle bodies were not to be lubricated as that can attract dirt and could swell the plastic. I never found that to be the case and clean with a light lube I feel is the way to go!