Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 S&S engine having problems "choke" mixture

Over the last week or so, the engine on my 2012 M3W is having mixture problems (or at least that is what it smells like). It is in the phase of transition from enriched mixture when cold to regular mixture (?14:1 approx). It starts popping and banging and can actually stall completely. It will not start normally and you have to use full throttle to get it to restart, which I feel means it is flooded. It also smells very rich. If you leave it a minute or so on idle after restarting, the problem goes away completely until the next cold start. It has only done 13,000km from new. I fitted new Lambda sondes (Bosch) about 2,000 km ago.

Any thoughts folks? I know the air cleaner is quite dirty with dust (I live in a dry dusty area of the south of France and recently we have had three Sirocco winds, which drop a lot of very fine Sahara sand dust). There is a new S&S filter on the way to me. I also have a crank position sensor kit ready to fit if required.

Wilson

Sounds like the Throttle Position Sensor (TPS)

I've replaced mine with Aliexpress TPS PF3C/00

You will need Protune to set up the replacement

See also thread https://www.talkmorgan.com/ubbthrea.../true/re-protune2-diagnostics#Post798193

Hi Chris,

do you also need protune to set up an OEM TPS? I have not had good luck with Aliexpress in the past, getting a dead Makita battery, which they failed to replace. Also I have no windows computers to run protune, nor do any of my family who will be visiting. We are all on Macs. Is the track in the original TPS cleanable. I did this with the TPS on my Jaguar Sovereign V12 30 years ago and it worked for another year. Will trial and error work on the rotation position of TPS?

Wilson

You will need Protune to install a replacement TPS or reinstall the original as you need to set the initial throttle position. It’s worth buying a cheap Windows PC off eBay just for Protune.

I don’t know of anyone who has managed to clean or repair one.

Aliexpress worked fine for me or you can get an OEM unit via MMC but I think they are about £90.

Alternatively M3WServices can supply and if required fit and setup a TPS.

I am not 100% convinced the problem is a TPS and I'll explain why. I have found a work around. If I start as normal with a closed throttle, where it starts instantly, I then leave it to warm up on a closed throttle until it starts to stumble after about a minute. I then increase the throttle very gently a tiny amount until it picks up to normal cold idle revs and wait another minute or so. Given it is quite warm at the moment, it is not long until the mixture changes from cold/rich to warm/lean and I can smell the changeover. I can now drive off normally with no problems. No reduction in power and no farting and banging. I have bought a cheap HP refurbished QWERTY laptop running on Windoze 7 from eBay UK and my daughter is going to bring it out when she comes to France in 10 days time. I have a new S&S air filter arriving today but I am not going to buy a TPS until I have plugged the laptop into my G56 ECU and run some diagnostics and only if I get the TPS error code (?13) will I buy a new one.

Chas and Steve at M3W services are checking to see what stock they have of Euro 3 and 4 TP sensors. I would get them to fit it except it is over 1,000 mile round trip to them as they are right at the other side of France from me

Wilson

The TPS doesn't seem to hard fail but just exhibits transient problems with starting or running.

You mention the G56 ECU - is it their map in an unlocked S&S or the Emerald?

For info, the S&S ECU starts the engine on a fixed map then switches to the (normally) closed loop main map as it warms up. This changeover happens pretty quickly within maybe 15 -30 seconds or so.

If you are having to crack the throttle to maintain cold idle then it could be the TPS just needs a very small tweak to it's alignment.

Chris,

Many thanks for the additional info. I fitted the G56 ECU back in 2016, so I am guessing an unlocked S&S ECU but I can ask G56. Anyway once I have a Windows computer in my hot sticky hands and able to run Protune 2, the diagnostics should tell me what the problem is. It misbehaved briefly last year and I thought it was a Crank Position Sensor, as it was hard starting as well. I asked the garage who store it over the winter to fit the new CPS kit I bought from Andy but they had no AF tools, sockets, spanners and hex keys, so they could not do it. The problem cleared itself after a few days anyway and it is only just this week any problems have appeared again. Over next winter, I am going to lend the garage a set of AF tools to change the CPS or I may ask my son when he is down in August, if he will do it. He is a development engineer in the defence industry with Frazer Nash, so may consider oily spanners a bit beneath him. I am just a bit chary about lending tools, as they either never come back complete or come back damaged.

Wilson