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rallysteve



Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2200
United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
Lumpy tickover again....
For pretty much as long as i have had my td5 it has had an intermittent lumpy idle. Hard to describe and its not a missfire, more like it surges every second or so. Give it a tiny bit of throttle and it is fine. Sometimes it does it when its warm, sometimes when its cold.

It has had two engines, new cylinder head, 3 sets of injectors, new MAF sensor, cleaned MAP sensor, new coolant and fuel temperature sensors, new FPR, fuel pump and probably other parts in my ownership. None of these have really made any difference to the issue.

It is not remapped and has the EGR blanked/removed.

Looking at the nanocom, there is nothing that sticks out as being abnormal. Temps etc all look as i would expect for the conditions. One thing which i have recently noticed though is that if I unplug the IAT/AAP sensor on the airbox, the tickover immediately turns silky smooth. Plug it back in and the idle goes lumpy again! Ambient pressure is showing as 99kPa and temp at 8deg which seems about right. With it unplugged, AAP shows as 3ish kPa.

Any ideas?

Cheers,
Steve 02' 110 TD5 Double Cab Rebuild Thread
84' 90 3.9 V8 Caged Pickup Build Thread - Now For Sale
Post #1021181 14th Jan 2024 5:52pm
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BaronDefenders



Member Since: 28 Jun 2019
Location: London/Cotswolds
Posts: 810
United Kingdom 2004 Defender 90 Td5 SW Santorini Black
It sounds as though the AAP sensor should be replaced! I wonder if, with the AAP being potentially faulty, the ECU is over-fuelling the engine when it needn’t do so, making it rich and lumpy. The AAP could be telling the ECU the temperature is lower than it actually is, thus inducing cold start. Just a thought. Charlie

1949 Series 1 80 (SOLD)
2002 Td5 90 (SOLD)
2008 Freelander 2 (SOLD)

1958 Series 2 88 Pastel Green (2019 LR Legends Best Restored)
1983 V8 110 Limestone (Previously owned by Tom Sheppard MBE)
2004 Td5 90 Santorini Black (Td5INSIDE Powered & Rebuilt by CSK)
2012 Puma 110 Zermatt Silver (Overlanding Build)

Instagram: @BaronDefenders
Post #1021308 15th Jan 2024 7:55pm
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NickMc



Member Since: 01 Oct 2014
Location: Norn Iron
Posts: 1572
Northern Ireland 2006 Defender 90 Td5 HT Bonatti Grey
Sometimes when it’s really cold I wonder is it just them 4 glow plugs on a 5 cylinder. I’ve seen the same problem on a few td5’s I could never work out why.
Post #1021309 15th Jan 2024 7:58pm
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