P38 Cold Idle Issue

Nialox · Apr 9, 2020

Hello

I’m back.

Car is a 1996 P38 DSE 160k miles manual.

in the last few months it’s had the water pump, plugs, injector leak off pipes etc.

I don’t have any history but my local Indy Landrover garage (who I can’t get to at the moment) says it’s had a fairly recent FIP at some point too.

onto the issue

car starts up fine first time in the cold. Maybe a little grumbly sometimes. turns on and idles at 1k before slowly dropping down.

whilst the engine is still cold however it’s very lumpy. Almost as if the engine is cutting out and catching itself just before it stalls. It can be very very rough

When you actually drive it it’s amazing, super smooth etc. And as soon as there’s a decent bit of heat in it and the engines warm The idle is perfect.

lift pump maybe?

Datatek · Apr 9, 2020

Nialox said:
Hello

I’m back.

Car is a 1996 P38 DSE 160k miles manual.

in the last few months it’s had the water pump, plugs, injector leak off pipes etc.

I don’t have any history but my local Indy Landrover garage (who I can’t get to at the moment) says it’s had a fairly recent FIP at some point too.

onto the issue

car starts up fine first time in the cold. Maybe a little grumbly sometimes. turns on and idles at 1k before slowly dropping down.

whilst the engine is still cold however it’s very lumpy. Almost as if the engine is cutting out and catching itself just before it stalls. It can be very very rough

When you actually drive it it’s amazing, super smooth etc. And as soon as there’s a decent bit of heat in it and the engines warm The idle is perfect.

lift pump maybe?

Worth checking the lift pump. Any smell of diesel under the bonnet? Do you have diagnostics?

Nialox · Apr 9, 2020

Datatek said:
Worth checking the lift pump. Any smell of diesel under the bonnet? Do you have diagnostics?

no smell of diesel.

No diagnostics.

literally a rough cold idle. Like it’s cutting out and bouncing out. Revs dropping and catching

Datatek · Apr 9, 2020

Nialox said:
no smell of diesel.

No diagnostics.

literally a rough cold idle. Like it’s cutting out and bouncing out. Revs dropping and catching

@wammers would know more but if the FIP has been replaced I would want to look at the modulation as a starting point assuming the lift pump is OK.

wammers · Apr 9, 2020

Nialox said:
no smell of diesel.

No diagnostics.

literally a rough cold idle. Like it’s cutting out and bouncing out. Revs dropping and catching

You would need diag on it. Sounds like idle control is a bit sloppy, idle is down to CPS, ECU and quantity control servo which should set a constant 750 RPM. If idle speed is below that you need diag to change it. At startup engine speed should be around 1100 to 1200 RPM depending on ambient temp then dropping to 750 after a short time. What is the indicated RPM at idle?

Nialox · Apr 9, 2020

wammers said:
You would need diag on it. Sounds like idle control is a bit sloppy, idle is down to CPS, ECU and quantity control servo which should set a constant 750 RPM. If idle speed is below that you need diag to change it. At startup engine speed should be around 1100 to 1200 RPM depending on ambient temp then dropping to 750 after a short time. What is the indicated RPM at idle?

Would that explain the difference in idle between cold and warm? As warm it’s much better

Uploaded some videos

Mark Piercy · Apr 9, 2020

Nialox said:
Would that explain the difference in idle between cold and warm? As warm it’s much better

Uploaded some videos

Wow, sounds like it's only just ticking over

You need to be able to see the diagnostic reading on the idle speed to start finding the problem.

Grrrrrr · Apr 11, 2020

Has it done it all the time you've had it? How long have you had it? Still under 6 months warranty from dealer?

As bodgit you could markup the FIP with a Sharpie pen, slacken the FIP slightly and tap it towards the engine by a mm or so and see if it makes it better. Put it back if not.

Better to follow Wammers advice but might be worth a punt.

Nialox · Apr 11, 2020

Grrrrrr said:
Has it done it all the time you've had it? How long have you had it? Still under 6 months warranty from dealer?

As bodgit you could markup the FIP with a Sharpie pen, slacken the FIP slightly and tap it towards the engine by a mm or so and see if it makes it better. Put it back if not.

Better to follow Wammers advice but might be worth a punt.

No it’s a relatively new issue. That’s why I’m thinking in tank pump.

I’m staying with my parents helping out during lockdown (mostly because they’ve a garage and I’m building a GPz550).

Their drive is on a massive slant. If I pull in forwards, in the morning my fuel level is massively dropped because of the angle, and it doesn’t like to start

however on the flat or the other way around it’s firing up first time.

possibly a combination of idle control and in tank pump?

wammers · Apr 11, 2020

Nialox said:
No it’s a relatively new issue. That’s why I’m thinking in tank pump.

I’m staying with my parents helping out during lockdown (mostly because they’ve a garage and I’m building a GPz550).

Their drive is on a massive slant. If I pull in forwards, in the morning my fuel level is massively dropped because of the angle, and it doesn’t like to start

however on the flat or the other way around it’s firing up first time.

possibly a combination of idle control and in tank pump?

If you look in the tech archive i give a process for checking the lift pump function.

dubbleRR · Apr 11, 2020

If it starts and runs fine with its nose down the hill and its bad facing up hill ,Thats the fuel running back to the tank ,then the bad idle is the air getting pumped out . This happened to me ,AT my mothers house,,,, .Do they all live on hills

,,,,I had a bad Leak off pipe ....Mine only happened facing up hill .,rest of the time it was fine .......RR...

Datatek · Apr 11, 2020

dubbleRR said:
If it starts and runs fine with its nose down the hill and its bad facing up hill ,Thats the fuel running back to the tank ,then the bad idle is the air getting pumped out . This happened to me ,AT my mothers house,,,, .Do they all live on hills ,,,,I had a bad Leak off pipe ....Mine only happened facing up hill .,rest of the time it was fine .......RR...

I can confirm that a faulty leak off pipe does that,

A duff lift pump will give the same symptoms especially if the tank is less than half full.

Nialox · Apr 12, 2020

Datatek said:
I can confirm that a faulty leak off pipe does that, A duff lift pump will give the same symptoms especially if the tank is less than half full.

it’s more of a slope side to side as opposed to anything.

here’s a video of it running warm to compare too

wammers · Apr 12, 2020

Wheres the fan shroud?

Mark Piercy · Apr 12, 2020

Through the my stereo speakers the engine is running quite evenly but that sounds like a snatching pulley to me?
I would try stopping the fan with a news paper to see if it's supplying the noise, if not remover the belts and check the pulleys and water pump. Then run it without the belts for a moment and see if the noise is still there.

brianp38dse · Apr 12, 2020

^ I was coming to the same conclusion as mark , have a look at the crank pulley damper that can make quite a noise / vibration

Mark Piercy · Apr 12, 2020

I had a failed intank pump and the fip would click unless I pulled the map electric plug off. This engine sounds calm under the noise.. I hope it's not a timing chain or tensioner noise. I would run it as little as possible until you or someone else can varify the noise, just to be safe. Do the belts and fan tests first. My pennies are in!!

Datatek · Apr 12, 2020

Mark Piercy said:
Through the my stereo speakers the engine is running quite evenly but that sounds like a snatching pulley to me?
I would try stopping the fan with a news paper to see if it's supplying the noise, if not remover the belts and check the pulleys and water pump. Then run it without the belts for a moment and see if the noise is still there.
View attachment 205392

+1 ^^^^^^^^ and check the crank pulley vibration damper as Brian said.

Nialox · Apr 13, 2020

Mark Piercy said:
Through the my stereo speakers the engine is running quite evenly but that sounds like a snatching pulley to me?
I would try stopping the fan with a news paper to see if it's supplying the noise, if not remover the belts and check the pulleys and water pump. Then run it without the belts for a moment and see if the noise is still there.
View attachment 205392

Never had a fan shroud.

I’ve run it before without the belts. And it royally buggers up the idle. Makes it 10x worse

Nialox · Apr 13, 2020

I’ve done the water pump this year with a metal impeller version. New belt and tensioner. Along with one of the pulleys.

I’ve had a look at the crank pulley damper before and never seemed to find much wrong with it.

I’ll ring up and get it booked in tomorrow.

I really am swaying towards the intank pump. Obviously video doesn’t convey noise. But it would make sense with the idle and the noise.

I think my garage has diagnostics as well. I’ll keep you updated.

P38 Cold Idle Issue

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