R400 K-Series hesitating at low revs, potentially after getting wet.

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Kimble
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R400 K-Series hesitating at low revs, potentially after getting wet.

Hi All,

I can see there's a lot of posts about with similar symptoms to this but I do think mine is related to the car getting rained on in a big way.  :(

In general, the car feels like it's misfiring or starved at low revs.  There is sometimes a significant lag when accelerating from low in the rev range and it's more jumpy than normal in first/second at low speed.

The car got very wet in one of the downpours recently and the problem seemed to start immediately after that.

Can anyone point me in the right direction of what parts/connections to check?  I haven't had my 7 long so am still finding my way around it.

Cheers,

Neil

Jonathan Kay
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1 The wells in which the spark plugs sit.

2 The lambda sensor. Experts, please: is this one of the situations in which disconnecting it as a test is a sensible tactic?

Jonathan

 

Kimble
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Thank you Jonathan.  I'll give both of them a check tomorrow and report back!

SM25T
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One or two plug wells full of water. Affected cylinders will have cold exhaust primaries when engine is running. Had this on mine after hitting a large flood.
Kimble
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Ok, took the plugs out, gave all the contacts a clean and put it all back together.  Seems to work fine.

Thank you all!  Great advice.

Jonathan Kay
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That's encouraging.

Was there any moisture down there?

Jonathan

Kimble
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Not that I could really see or feel but there was a little bit or arcing on the top of one of the plugs and some white residue on the rubber inserts that made me think water had been ingressed.  I used some WD40 type stuff to try and repel a bit of moisture before refitting.   I did notice one of the plugs was quite oily up at the thread which is maybe an indication of loss of ignition in that cylinder(?).

She felt much more herself when I took for a run out at lunch time.  Just how I remember.

Jonathan Kay
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Thanks

Jonathan

rj
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Another issue I've seen is if the mapping connctor gets wet, the ECU may think you've started mapping (!) The engine ran very poorly, but when I connected the mapping lead to ask it why it was unhappy, happiness came back. In other words it seems that the inputs for mapping on the MBE is high impedance, and as such sensitive to moisture.

 

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Kimble
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Resurrecting my old thread here as I still think my K400 has a specific problem around the 3.5 - 4k rev range.

In general, it just seems a bit gutless around that point and I can hear a deeper 'blowy' sound from the exhaust and feel some hesitation in the engine..  If I add more throttle and get through that point the engine picks up and away she goes.

I've checked all the spark plugs and connectors with some liberal use of WD40.  I have also disconnected the lambda sensor and the behaviour was much the same.

It feels like I am going to need to hook this up to easimap or some software to get some better readings.

It's a 2004 R400K with a MEMS box with 'Road' written on it.  My standard ODB2 reader couldn't read anything from the device so I am guessing I need this lead and then I should be able to plug a Windows box with Easimap to read from the MEMS unit.  Is this correct?

https://www.sbdmotorsport.co.uk/MBE-MAP-KIT-3-CAN-basic-can-mapping-kit-for-mbe-can-based-ecus.html

Once again, thank you for all your help.

SLR No.77
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It's a 2004 R400K with a MEMS box with 'Road' written on it"

"MEMS" is the specific Rover ecu that pre-dates R400 Ks with rollerbarrel throttle bodies, do you mean "MBE"?

Stu.


 

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