Jgray2022

Bit stumped here. I’ve taken car to Ford and they’ve reported nothing wrong. I’ve no engine management light either.

Problem: car revs sometimes surge when down at idle. Say the car idles normally at approx 700/800rpm. All of a sudden however, the revs will drop down to 500 and the car shudders, revs jump back up to the normal idle, then drop back down to the 500, then jump back upto normal idle.

It seems to happen randomly, but a sure way to induce it would be to have the A/C turned on when approaching a stop. Once you stop it’ll do the double surge thing then go back to normal idle.

Also I notice, with the A/C turned off, sometimes the idle will sit at 1500 revs steady. Especially likely to happen after hard driving. But if I click the A/C on, the revs immediately drop down to 500, bounce to 700/800, back to 500, then back to 700/800 where it then idle steady.

Anyone any ideas? Is it a load issue? Should I try replacing the battery? Any sensors going dodgy that could cause this kind of issue?

GVK.

Sounds like an air leak but easy to say from here, ideally needs a smoke test to find if not obvious.

Jgray2022

The issue is super weird because the idle doesn't mess up every time. Ford did tell me before they had smoke tested it though and all was fine. (I'll ask them to redo though, have car in for service soon anyway)

Anything else you can think of that may cause this kind of issue? I have a Carly obd reader so there's some live data values I can look it, but not sure which to watch for the idle

Wish there was a specialist ford garage here in Scotland, but doesn't seem to be