Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Misfire on warm up

Hi everyone.

Been a 3 wheeler for just over a year and 3,000 happy miles but find myself in need of your combined knowledge.

My car is 2018 with a stage 2 upgrade. It has been back with KH for a month trying to resolve a misfire when cold. It clears once warm, but until then has a severe hesitation when driving gently or on half throttle. Give it full gas and it pulls through, albeit not cleanly. Not sure the neighbours or local constabulary would understand. It is bad enough to start looking for somewhere to pull over but hasn't fully failed on me yet.

The problem hasn't always been there but has come on over the last 500 or so miles.

To date it has had several ECU's trialled along with every sensor replaced one by one - but still the problem is there. Sensors, plugs, leads, exhaust sensors, cats - pretty much everything electrical or fuelling but still it persists.

Convinced the problem is not mechanical as it clears once warm, the problem is getting it warm.

Next option is a full engine harness change but before then thought I would reach out to all the experience here to see if anyone had any suggestions or experience of a similar issue? KH determined to resolve but a harness change is a big job apparently.

Any ideas? Any known places where the harness may chafe and short out a key sensor?

I just want my baby back! The space in my garage is filling up with rubbish!

Do you get any ECU codes? have you tried reading live ECU data with S&S ProTune?

If your mechanic did not use the S&S Pro Tune diagnostic software first thing, he's not much of a mechanic.

I'm deeply offended by the expensive process of changing components in the hopes that you will stumble on the answer.

The Pro Tune software is free from S&S, all you need is a laptop. It will reveal stored error codes as well as show real-time (while driving) how each sensor is functioning as well at fuel/air ratio, timing, etc.

I think you primary problem is that you have the wrong mechanic.

No fault codes in the ECU. The car is with KrazyHorse. I am confident they know their way around the 3w, but this seems to have them stumped. They have even been on the phone with S&S directly to try to route cause. Agree that random part changes is not very scientific but after working through the diagnostic data that is what they have had to resort to. I will double check what dynamic data (on the road or on their rolling road) shows. That hasn't come up in conversation so far as I didn't know the software gave live data also. Thanks for the support.

Is the problem on one cylinder or both?

Have KH tried hotter spark plugs?

Hi IMHO. Not sure to be honest. When driving it feels like it is starving itself so I assumed both. Fuel pressure all checks out ok and they have changed the pump. I have not witnessed the issue in the workshop as it was dropped in for a service and I assumed a tweak to the mapping. They found a couple of other issues that we hoped had cured it but this warm up issue remains. I’ll ask them tomorrow as I am due my weekly update.

War Bird - Currently running on standard plugs but again they have been changed. Any recommendations on alternatives?

Sounds like the ECU map may not be happy during the warm-up phase. I wonder if the problem could be one of the sensors feeding back incorrect info to the ECU?

Stepper motor controlling cold idle?

Piston rings could be k-nackered ?