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Van Diesel

Member Since: 12 Oct 2013
Location: Suffolk
Posts: 177

1986 Defender 90 V8 Petrol ST Auto Pennine Grey

Complete loss of power at 3000rpm

Hoping someone has some clues on this

90 pick up with a 3.9 V8 from a 93 Disco. Starts and runs fine but a bit rich.

Sitting still in neutral or park (auto box) I can rev it up into the red if I want to. Get going down the road and just about at 3000rpm, I lose all power, throttle goes dead. if I pump throttle I can hear the K&N sucking air but noting else. After about 2 or 3 seconds, once revs have dropped back, throttle comes back to life.
ECU, amp and Magnecour leads about 5 years old from RPI. New Idle air control valve. No issue before this was changed apart from high idle, which the new IACV cured but now this problem. Related?

Have checked inputs with multimeter on TPS lead but with the plug type on the wires i can't really check output on signal wire. Even with the TPS unplugged, I'm still getting issues so don't think this is the cause.
Any ideas?

Last edited by Van Diesel on 4th Jun 2022 4:14pm. Edited 1 time in total

3rd Jun 2022 5:03pm

rallysteve

Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2237

2002 Defender 110 Td5 DCPU Keswick Green

Have you checked if the vacuum advance is working on the dizzy?

I would also check the ignition timing.

Steve 02' 110 TD5 Double Cab Rebuild Thread

3rd Jun 2022 6:50pm

custom90

Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20430

Is it turbo charged or NA?

If turbo charged then maybe Turbo related? I’m no expert but I mention it as when I had issues with mine with the turbo actuation it would rev fine but when under load I.E. whilst driving you’d just have very little power indeed and feel completely gutless as the turbo was not active at all and no boost.

Just something to think about, and boost leaks etc as well. $W33T $0U7H3RN $UG4R
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3rd Jun 2022 9:18pm

discomog

Member Since: 09 May 2015
Location: Notts/Lincs Border
Posts: 2528

2015 Defender 90 Puma 2.2 XS CSW Santorini Black

Is it a faulty sensor (possibly Lambda) causing it to go into limp mode? Defender 90XS SW
Mini Countryman Cooper S
Morgan Plus 8

4th Jun 2022 7:26am

Van Diesel

Member Since: 12 Oct 2013
Location: Suffolk
Posts: 177

@Rallysteve

Vacuum advance seems ok. Dizzy is fairly new. I may get the timing checked.

@custom90steve

It's normally aspirated so no turbo to effect things.

@discomog

It doesn't really go into limp mode, it just loses all power under the pedal for a few seconds, once the revs drop off it's back to normal, until you hit 3000rpm again.

I'm wondering if the ECU is picking up a wrong signal from the TPS? Like it's telling the ECU that the pedal is flat to the floor, or that sort of thing.
Can't think it's fuel related as guessing it would splutter before cutting out. It revs strongly all the way up to around 3k then it's like someone cut the throttle cable. I've checked the throttle assembly and it's all smooth, no snagging. Plus it revs in neutral to the red line with no issues.

4th Jun 2022 1:22pm

jpboost

Member Since: 13 Apr 2021
Location: Gatwick
Posts: 377

2014 Defender 110 Puma 2.2 SW Keswick Green

Crank Sensor?

I've had one break down before (on a different engine entirely) and it coped ok at lower rev's, but showed faults at higher rpms.

4th Jun 2022 1:49pm

Van Diesel

Member Since: 12 Oct 2013
Location: Suffolk
Posts: 177

I've just uploaded a couple of crappy quality videos to Youtube to see if it helps anyone.

This one you hear it die and the short time it takes to come back to life before it dies again. Sounds like i'm lifting off, but I'm not.

https://www.youtube.com/shorts/J_66WYBCCgo

This one just cutting out as it hits 3k rpm
https://www.youtube.com/watch?v=WCH1hAFEGFc

4th Jun 2022 2:09pm

discomog

Member Since: 09 May 2015
Location: Notts/Lincs Border
Posts: 2528

I'd agree with you, it certainly doesn't sound like a fuel problem. Don't know if you've had a chance to check ignition timing as someone suggested but I doubt it's that - my 3.5 EFI is fairly critical on timing but you soon know about it as it either pinks under throttle or runs on after switching off. Sensor/ECU seems to be the most likely. Defender 90XS SW
Mini Countryman Cooper S
Morgan Plus 8

5th Jun 2022 9:43am

Van Diesel

Member Since: 12 Oct 2013
Location: Suffolk
Posts: 177

Not had a chance to get timing checked but no pinking or symptoms you'd associate with timing.
I think it's a sensor of some sort or an ECU issue?

Could it be a temperature sensor? Presumably wouldn't just cut the power if it thought it was too hot though? Same with MAF, it wouldn't just cut off there would be other signs. Throttle position sensor seems like a possible link but don't know enough about them. Would a break in the contact that the wiper follows do that?

5th Jun 2022 5:34pm

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