My Range Rover has a strange hesitation when at low revs under load. I vaguely remember noticing what I thought was a misfire when climbing the hill to the farm the night I bought the car. I put it down to it needing the timing chains doing and didn’t think any more of it.

The night I drove it for the first time after doing the chains I thought I noticed it again when climbing the lane.

I can now confirm that there is indeed a hesitation on the car. Most of the time you don’t notice it.

When the car is in a higher gear and under load with the revs kept low (1800rpm or below) you can feel a hesitation from the car. Probably best compared to a stutter. If you accelerate through it and get the revs over 1800rpm it clears instantly. If you paddle the car down a gear and get the revs up it clears instantly. If you’re pushing on a bit so the car keeps itself in a lower gear with the revs being a bit higher it doesn’t happen.

I’ve checked the fault codes several times and there are no codes logged. I’ve driven the car with SDD connected and it’s not logging any misfires.

Tonight whilst the car was in the workshop I put the ignition on, wedged the throttle wide open and then smoke tested the car via the intake at 20PSI and can’t find any smoke escaping from anywhere either.

Has anybody got any suggestions as to what might be causing it? I was kinda hoping it would be a vacuum leak or something easy to fix but it doesn’t look like it. The car idles beautifully, sits on cruise control on the motorway smooth as silk and goes like a stabbed rat when you boot it so I’m absolutely certain that it’s not a fault with the timing.

Thanks,
David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Last edited by dhallworth on 23rd Oct 2023 10:19pm. Edited 1 time in total

It made no difference I could tell but worth checking this pipe....

https://www.fullfatrr.com/forum/topic58105.html

 Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Cheers Pete.

That one is a right pain in the backside to get back on. It is sealing though as when I removed it tonight during the smoke test I was getting smoke out of it. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Hi David,

A few thoughts,

Have had a similar issue on different vehicles and the solution has been to clean the throttle body.
Be very gentle when opening them manually ie against the motor as they can be easily damaged. Pay particular attention to the area around the disk and housing in the closed postion and edge of the disk flap as obviously this is where they can stick.

Another thought would be the airpath routine on sdd which the sdv6/8 have but unsure on 5.0?

Last one is maybe gearbox torque converter locking/unlocking?

Great work and always interesting

Look at misfire counters being logged on the iid tool, coil pack on its way out imo at certain conditions

Good luck

Ah only skip read. Didn't see you had looked at misfires, can't edit on phone.

Still reckon it could be a dodgy coil pack though....

I’ve cleaned both MAF sensors and the throttle body this evening. Starting with the simple things first.

Situation normal for a 5.0 SC… the fuel light is on! I’ll take it for a run later on and see if it makes much difference.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I’ve just driven from home to Costco. All the way to the Kingston Bridge (18 miles) the car was absolutely perfect. Crossed the flyover at the airport in 6th gear at 1200rpm up the slope with no tugs or hesitation so I was quietly confident that it was fixed.

We got stuck in traffic on the Kingston Bridge due to the roadworks and by the time we started to accelerate gently I could feel the hesitation was back.

I need to update the firmware on my IID tool this evening as it’s not reliably reading the live data and the SDD laptop balancing on the seat is nowhere near as convenient.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

I'd suspect the coil pack if it's misfiring after being stuck in traffic and it's got hot. This is going way back but on software monitoring for another car I had it was possible to record ignition misfire events but not sure if the GAP IID tool can do this? 2012 TDV8 Vogue (L322)

Managed to sort my IID tool out today.

Patrick at GAP sent me a firmware update for the IID tool which in turn flashed the engine ECU and then I was able to monitor all the live values perfectly.

I monitored the misfire counter all the way from Aberfoyle to home today (29 miles) and there were no catalyst damaging or emissions related misfires logged.

Climbing the lane to the farm shows this hesitation at its worst so I then started to monitor the readings coming from the MAF sensors and both were very similar to each other.

I then looked at the fuel trims and believe I’ve found the cause. I think I was on the right track with a vacuum leak so need to smoke test the car again when it’s hot. If that doesn’t reveal anything then it might be time to have a look at replacing the oxygen sensors.

The engine ECU was flashed when we were in Aberfoyle so the adaptions were reset. This screenshot was then taken 29 miles later with the car idling on the driveway.

Click image to enlarge

Popped in to see the local JLR specialist today. Explained what was going on with the car, explained that there were no misfires, both MAF sensors were giving very similar readings and that the fuel trims were off from where I'd expect them to be.

He said that in his experience when they have a vacuum leak they usually throw the engine management light on pretty quickly due to the mixture being lean.

It's booked in for a high pressure smoke test on 15th November (soonest they could do) and if I find anything and cure in the meantime I've to let them know. I said I was pondering it being a lazy oxygen sensor pulling the mixture away from where it should be and he said that was a good shout and could be a possibility.

There's someone on eBay selling genuine LR oxygen sensors for a good price so I'm tempted to change the 2 front pre-cat oxygen sensors just to rule them out before it goes to him.

David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

Yep, those fuel trims are way out if you reset adaptions 29 miles before, it only takes a short drive for them to stabilise, and I agree an air leak is the likeliest as they are positive numbers....

Good idea to change the oxygen sensors, one less thing to worry about...

Have you checked the fuel pressure, that pair of high pressure pumps on the 5.0 are known to suffer and give problems and it's a free check with an IID..!! Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

I’ve not checked the fuel pressure actually. It doesn’t give any issues when under wide open throttle and using full power so I assumed they were ok.

Do you know what the fuel pressure should be?

Thanks
David. 2002 4.6 Vogue SE - Alveston Red with Lightstone Leather
2007 Range Rover Supercharged in Java Black with Ivory Leather
2012 Range Rover 5.0 SC Autobiography in Indus Silver with Jet/Ivory Interior
2012 Range Rover 4.4 TDV8 Autobiography in Baltic Blue with Sand Interior

The IID says what is being called for and the sensors tell you what it's getting, so a quick, easy check...  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Had a quick peek tonight at the fuel pressure.

At 70mph on cruise control on the motorway:

Click image to enlarge

Click image to enlarge