McLaren investigating Fernando Alonso's new F1 engine after US GP

Alonso was robbed of a points finish by an issue with the new 'phase four' power unit raced for the first time at Austin after an initial trial in first practice in Russia a fortnight previously.

It is currently planned for team-mate Jenson Button to receive the system at this weekend's Mexican Grand Prix.

However, McLaren and Honda are to conduct analysis of the system over the next few days before making a decision on a way forward for the race at Mexico City

"There will be an investigation into what happened," McLaren racing director Eric Boullier told Autosport.

"We introduced the new engine spec, but 10 laps before the end, with Fernando sixth and Jenson seventh, we had an issue with Fernando's engine and that is why he finished 11th.

"We had a loss of power at some stage. It took us some time to work out what was wrong and how to play with the mapping to avoid the problem.

"We recovered it by changing the mapping, but by then it was too late as he had lost lots of positions, so we need to understand what happened.

"We need to see if there is any damage and then we will have to take a decision to take the new engine for Jenson or not."

Boullier at least feels a good degree of progress has been made with the new power unit, adding: "With both cars running the same chassis configuration you can compare, look at the data to understand if it's better.

"When you bring a new engine, it's not going to be one second, so you have to carefully analyse all of the data, but clearly there is progress."