Really random idle revs

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Stan Thomas
Club Member
Posts: 263
Joined: Thu May 27, 2021 2:36 pm

Re: Really random idle revs

Post by Stan Thomas »

Just a thought - but have any of your vacuum pipes gone "soggy".

I say this because we had a similar problem to yours and it transpirered a soft vacuum pipe was sucking "closed" when the engine was running but appeared O.K. when the engine was stopped.
lsowden12
Club Member
Posts: 48
Joined: Thu Jan 19, 2023 7:05 pm

Re: Really random idle revs

Post by lsowden12 »

friend of mine brought up a very good point. The first time this started happening was the day after I was testing for a battery drain and was consistently disconnecting and reconnecting the battery all day. He thinks the ECU got confused and has forgotten to program the right air fuel mix ratio. I have disconnected the battery entirely and will leave it off overnight and see if that resolves anything. I will also try the brake cleaner trick tomorrow if not :)
1994 Rover 214SEi - Nightfire Red / Tempest Grey
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g259fsg
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Posts: 298
Joined: Sun May 20, 2007 6:38 pm
Location: Dunfermline

Re: Really random idle revs

Post by g259fsg »

Had this problem on our 214 GSi after it had been in the garage for a head gasket change. Idling was somewhat erratic, although it was initially fine when I collected the car. Took it back to garage, and the mechanic (an ex-Rover guy) went straight to the vacuum tubes. One goes to the MAP sensor on the ECU, but it was the other one which was the culprit. It goes off the manifold up to an air temperature sensor/valve in the air filter and then over to a flap arrangement in the air intake to switch to warmer air off the exhaust manifold. Don't think any of that works now, but the mechanic found one of the vacuum connections was loose. Fixed the problem immediately. I did fit some new tubes later to be sure and it has not re-occurred. Don't know if your car has this, being a later model, but you could block this tube at the manifold to see if the circuit is causing trouble. If air gets in, it destabilises the mixture and the ECU starts hunting. Make sure there aren't any other air leaks round the throttle body.
1990 Rover 214 GSi (VIN 222977)
1964 Humber Super Snipe Series V
1965 Humber Sceptre Mk.1
1966 Hillman Minx Series VI
crepello
Club Member
Posts: 1987
Joined: Thu Feb 18, 2010 2:47 pm
Location: Herts

Re: Really random idle revs

Post by crepello »

Thought: Do vacuum non-return valves to the brake servo fail sometimes?
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