Car violently jolts when not under load

[ThreePointFive]

It's the MAF sensor.

[Bowie69]

Ah here we go:

 

That's the IAT sensor holder/brackety adapter ring, you have no MAF.

[ThreePointFive]

So we can probably rule out the MAF being to blame, then....................

 

[FridgeFreezer]

1 hour ago, ThreePointFive said:

So we can probably rule out the MAF being to blame, then....................

See, we're making progress already!

[Eightpot]

I've had some pretty shonky old african import landys with wear in virtually every part of the transmission that would do this, particularly behind V8s, the only way to stop them was to dip the clutch and try again.   As a first step I get them up on stands, whip the pto cover of the back of the transfer box and turn a wheel back & forth and watch what each component does - surprising how much rotation you get from a few mildly worn components and a bad A frame bush.  Hopefully yours is just down to a bit of tinkering with the engine tune. 

[Happyoldgit]

Yep, I can vouch for this. Worn half shaft, prop and other transmission splines, bearings past their prime, worn diffs, sticky or slack UJ's, transmission brake high spots, bushes etc can all add up to a huge amount of backlash. One notable old high miler SWB Series something-or-other I had back in the '70's had gigantic amounts of slop in the drivetrain, any minor engine pops and bangs would have the whole thing kangarooing alarmingly until the clutch was dipped and load taken off for a bit.

[ThreePointFive]

1 hour ago, Happyoldgit said:

Worn half shaft, prop and other transmission splines, bearings past their prime, worn diffs, sticky or slack UJ's, transmission brake high spots, bushes etc

First we rule out the MAF, then we narrow it down to being a part fitted somewhere in, on or around the car, all in one page. Slow down, I can't keep up with this progress.

I think you're right, it's a culmination of many things being set off by the engine issue.

[FridgeFreezer]

The slack doesn't help - it's a cycle of the engine moving through different parts of the map as the slack in the system is taken up & released, a bit like a learner driver kangarooing down the road. The solution is to smooth out / calm down the areas of the map where it sets in, but how exactly you do that is for the grown-ups to explain as sometimes it's counter-intutive (or my perhaps my intuition is 180 degrees out, more likely!)

[ThreePointFive]

You've hit the nail on the head as I obviously mapped-in this problem, I am not sure I will be suitably qualified to identify and cure the cause.

After having the gearbox rebuilt, doing the UJs and rebuilding the axles, I shouldn't have any play anywhere. But I do.

It's a shame as I really wanted to show the car to family this Christmas for the first time, which involves a long drive.

[Bowie69]

There's always play in things, always.... has to be there so when things warm up they don't bind.

I don't think there's anything wrong apart from a bit of tuning.... and you won't do harm driving it like it.

If it is shunting you can probably get it to do it in neutral, and see what's going on safely, and then see which bit of the map it is, and flatten everything out a bit.

I doughty you've mapped it in, the stock map that comes installed does it, at least it did on LGT.

Edited December 19, 2022 by western
Empty space edited out

[Bowie69]

....and it appears the whitespace issue is back.

[landroversforever]

21 minutes ago, ThreePointFive said:

You've hit the nail on the head as I obviously mapped-in this problem, I am not sure I will be suitably qualified to identify and cure the cause.

I suspect it's more that it's just not been tuned at all at that part of the map. 

[ThreePointFive]

I think I did tune it this way as I was trying to get better low-RPM performance from it, as it kept wanting to stall unless I gave it more throttle than seemed reasonable.

Raising the idle speed did a lot to help but the shunting was already a thing by then. I'll try reverting to a map where this didn't happen and then compare against the newest one to see where it went wrong. I want to keep as much of the current map as I can.

[western]

1 hour ago, Bowie69 said:

....and it appears the whitespace issue is back.

Just edited the space out. 

[FridgeFreezer]

I've got quite used to driving with the problem, dipping the clutch when it starts / when you are in a situation it will do it, and then bring it back up gently so you're not jerking the vehicle. I find shifting up earlier helps too.

[Eightpot]

Just thinking, last time I put a 3.9 in a 110 some years ago, I couldn't find the road speed sensor that connects to the speedo cable, so ran it without.  From memory the point of the thing was to reduce fueling at low speed to avoid surging (which it did!)  Different system from yours I know, but yes the tuning at low speeds definitely did cause an otherwise mechanically tip top 110 to buck around a bit till it had chance to stretch its legs and get some speed up. 

[ThreePointFive]

To update this, I took onboard everything I could from the advice given and I have found some things and have some work to do.

I found that the front rear UJ had a bit of play in it where it would move 1mm by hand when bolted up. Also my handbrake has lost effectiveness and isn't holding the car on big slopes. I'm blaming water ingress coupled with the freezing weather when parked.

I have sent off my props to D&F Props as recommended elsewhere, looking forward to getting those back and hopefully addressing a mild 50mph vibration I was feeling but ignoring. I'm going to take a look at the handbrake mechanism while the props are off and make sure it's all seated properly. That's two areas of potential cause.

While this is all apart, I'll replace all my engine mounts with the Glencoyne ones. At least they are a known-good and rules them out from future diagnosis.

As much as it pains me, I have bought a PWM idle valve kit from Nige. Having the car almost stall when just going from lock to lock was the last straw and it's a safety consideration as much as anything due to how unpredictably it drives while cold.

Having then sorted as much mechanical causes, I'll ask for a trip to @Bowie69 's House of Flying Laptops and a tuning session (finally) to try to get rid of the last symptoms.

I'll post results, it may help someone some day. Or provide the next owner with insight into why the car was so cheap.

[Snagger]

Hopefully, the props will fix the vibration.  I have a minor vibration from the front at a similar speed in my RRC.  I replaced the UJs, CVs, wheel bearings, brake discs and tyres and fit HD drive flanges with no change.  I even fit a replacement used diff with absolutely no effect.  The stub axles have a tiny bit of wear on the bearing seats, but barely measurable, but I have some suspicion of them or the internal bearings.  I have a complete replacement front prop to go on, even though the original prop is not damaged and doesn’t appear to have spline play, which would be done first before replacing the stub axles.  I’ll be following your progress, just in case I have the same fault.

[elbekko]

3 hours ago, Snagger said:

Hopefully, the props will fix the vibration.  I have a minor vibration from the front at a similar speed in my RRC.  I replaced the UJs, CVs, wheel bearings, brake discs and tyres and fit HD drive flanges with no change.  I even fit a replacement used diff with absolutely no effect.  The stub axles have a tiny bit of wear on the bearing seats, but barely measurable, but I have some suspicion of them or the internal bearings.  I have a complete replacement front prop to go on, even though the original prop is not damaged and doesn’t appear to have spline play, which would be done first before replacing the stub axles.  I’ll be following your progress, just in case I have the same fault.

I replaced the front prop on my P38 because I kept having a vibration and it kept eating U-joints. I read a theory somewhere that you can only do so many U-joint replacements until the ears on the prop deform, and it sounds fairly plausible. Much better now with a new prop.

[FridgeFreezer]

I'm just going to throw propshaft phasing into this discussion, I forget the details of it but there's definitely something with front props and being phased a number of splines out, I vaguely recall they don't always arrived correctly phased from some suppliers and fitting them the wrong way round may not help either.

I'm sure there have been a couple of good tech threads on it.

[ThreePointFive]

I didn't know until I looked into having these balanced that the point of a double carden prop is vibration elimination as much as increased articulation - which is why they were fitted to Discos (not so someone could come along and put a lift kit on it, who knew). I'm not going with double cardens of course, but it was interesting to read that they had to resort to that. It implies it's impossible to fully remove on a single jointed prop.

Phasing is one thing I believe I got wrong, and why I'm getting the (mild) vibration. I'm hopeful they will send back my props assembled or at least with marks to align them. I saw a video of how a single UJ cannot keep a constant velocity through its rotation on anything other than straight angles and the need for a UJ at both ends but offset by 90 degrees is to balance this out. Easy to get wrong and I wonder how many have been assembled in home garages with the joints neatly aligned.

I don't know why this one UJ is at fault, doing them with a vice, a socket and a hammer in my kitchen probably wasn't the best environment but I am surprised that 1000 miles has done for it, especially when greased twice in that period. I am going to look again at the heat shielding around the exhaust near the front though as I know others have had their grease cooked.

I am sure that the prop is not the (main) cause of the jolting that started this, though.

[western]

11 hours ago, FridgeFreezer said:

I'm just going to throw propshaft phasing into this discussion, I forget the details of it but there's definitely something with front props and being phased a number of splines out, I vaguely recall they don't always arrived correctly phased from some suppliers and fitting them the wrong way round may not help either.

I'm sure there have been a couple of good tech threads on it.

On a 90/110/Defender the front prop ujs are out of line aka out of phase

Note in workshop manual states - - universal joints in front prop are by design NOT assembled inline with each other, the alignment marks on sliding joint & prop shaft must be inline when assembling. 

Rear props are ujs are inline aka in phase 

[Snagger]

The impulses would be eliminated if the yolks are parallel (like on Series vehicles), but they couldn’t do that on the front of coilers.  Because the UJs on those both tip the same way, they would amplify each other if aligned, so phasing them by 45 degrees gets the best average rpms to minimise vibration.  As the effect from one UJ increases, the other’s will decrease every sector of rotation.  It still gives a small amount of oscillation because the amount of the effect is not linear with degrees of rotation (ie at 45degrees, you don’t get only half the effect from each UJ), but it seems to work well enough if everything else is in good order.

I need a DC front prop for my 109 as the aft UJ is nearly straight but the front UJ significantly deflected since fitting a coiler front axle.  The Series engine and transmission sit much lower in Series vehicles, so the prop shafts are much shallower, so it matches neither the Series nor coiler arrangement with the hybrid axle.  As the amount of rotational oscillation increases logarithmically with the deflection angle of a UJ, two UJs deflected half the amount have much less than half the oscillation of a single UJ at the same angle.

[ThreePointFive]

7 hours ago, western said:

On a 90/110/Defender the front prop ujs are out of line aka out of phase

Note in workshop manual states - - universal joints in front propare by design NOT assembled inline with each other, the alignment marks on sliding joint & prop shaft must be inline when assembling. 

Rear props are ujs are inline aka in phase 

Just when I think I know something, it gets corrected on here! I read they should never be in phase as it creates problems, so both of mine were out of phase. Ah well.

[uninformed]

A DC does not increase articulation, in fact they have a limit that is less than a wide angle traditional uni joint.

 

Proper DC has the DC with the majority of angle change from flange to shaft and the standard uni end should be only 1 degree. 
 

The Internet will say zero degrees for the standard uni end, but you want at least 1* so the needle rollers get turned . At zero they won’t and can brinell.