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Discussion Starter · #1 ·
This has bugging me for a while--perhaps someone will have some good idea....

I have a 1998 Mondeo w/ 1.8L/16v petrol "blacktop" engine. Whenever the weather gets cold or it rains a lot, and I shift to neutral while the car is moving (like before an intersection, etc), the RPMs jump to 1500 and stay there until the car comes to a complete halt, at which point the RPMs go to the normal 800. Alternatively (which is what I saw today for the first time) the RPMs drop to 500 while cruising in neutral, and recover when the car stops.

Also when the engine is started while the outside temp < 5-10C, the RPMs often start to oscillate up and down until gas is depressed.

What might or might not be related to this is that last Summer (while raining like hell) the car lost power and stalled at full speed on a motorway (while shifting from 5th to 4th gear) and could not be restarted for 3 hours.

I took the car to a shop twice already but they could not reproduce the problem. I have gathered some pointers, like the idle valve, MAF, and the lambda probe, but I would like to get the opinion of experienced MEGers.

Cheers,

acnurb
 

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MEG Corporal
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801 Posts
maybe you should not leave it in neutral on the motorway cruising. i think this has something to do with confusing the ecu and messing all the parameters as speed, fueling, cooling etc. ie a few times as i am comming off a motorway at the junction when i stop, the eng keep the revs up 1500~2000 in order i believe to cool down the lump.
just opinion anyway.
 

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MEG Corporal
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866 Posts
You shouldn't be shifting to neutral while the car is moving. The VSS tells the EEC that the car is still moving and the EEC thinks that you are in the middle of a gear change and it adjusts the revs accordingly. Its just trying to keep your gear changes a lot smoother and this is not a fault.
 

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SDR said:
a few times as i am comming off a motorway at the junction when i stop, the eng keep the revs up 1500~2000 in order i believe to cool down the lump.
just opinion anyway.
It keeps the engine revs up to make sure it keeps the vacum pressure up so your brakes work as normal. If its not working you'll find your brakes are harder to press with the car moving and engine ideling as the vacum pressure drops off when the revs go below 1000rpm
 
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