DaytonaRS7
Full Access Member
the stumble at idle would make me think vacuum leak.
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the stumble at idle would make me think vacuum leak.
Someone on landroverforums is having what appears to be the same problem. He’s tried to get on this forum, but can’t seem to get a response from the admin.
I’ve been trying to brainstorm with him and just noticed yesterday that this might be the same problem you’re having. 2015 LR4 with close to 100K as I recall. Intermittent surging rough idle and his STFT and o2 readings bounce around from rich to lean when he’s having the problem. o2 seems to read rich when he’s not having the surging idle.
I don’t have any new ideas yet, just thought I’d mention it.
https://landroverforums.com/forum/lr4-38/daily-intermittent-rhythmic-engine-shudder-104587/
Do you have one of those propane **** torches? If it is a vacuum leak, you might find it by opening that up a little (not lit, obviously) and moving it around the engine compartment to see if there's an area where the idle smooths out or picks up.
To answer the question on the temp sensor, the one in the front is not part of the t-stat. It is sold as part of the lower radiator hose just below the t-stat, but I think it is replaceable separately. I’m not sure how the ECM uses the two signals together in the fuel control system, but I believe both play a role.
I’m also trying to think about the possible relationship to the DTML pump. As I understand the system, the DTML pump pressurizes the tank, which is connected to the purge cannister, which is in turn connected to the purge valve. When the purge valve opens, it vents the cannister to the air intake. So, if there were a leak in the evap system, it could create a vacuum leak in the engine only when the purge valve was open (or if the purge valve was faulty). I recall someone in these forums reporting that a garage discovered a leak in the DTML with a smoke tester. Can’t remember if it was causing a vacuum leak, and can’t find the post.