Hi all,

So for quite some time I've had shuddering during acceleration at around 1800rpm to 3000rpm. Its getting very noticeable with all the door trims and steering wheel shuddering during any take off.
The car is lowered and manual.

I've replaced quite a few parts in the last few months to replace broken parts and hopefully fix this problem.

Parts replaced/Work conducted:
- 4wheel alignment. No problems with camber found.
- New tyres on front. Wheel balance conducted during installation.
- All 3 engine mounts replaced in last 20,000kms. Drivers side replaced 15,000kms ago. Front and rear replaced less than 2000kms ago. Transmission mount worn, but not torn.
- Passenger side driveshaft replaced last week. Drivers side replaced 15,000kms ago. Both visually look fine.
- Strut tops and bumpstops replaced 10,000kms ago with Kyb ones from Rockauto.
- Brake rotors seem fine. Shuddering not during braking.
- Lower control arm bearings look ok. No split boots and wheel is not loose when shaken.

Not sure if its relevant but when the car is warm and its turned off and on again, it has a very low rpm rough idle. Cold idle has a cyclic/repetitive hissing noise. Power seems down under 2400rpm.

Does anyone have any ideas on what could be causing the shuddering? It seems to be getting really bad now. Could it be the clutch plate shuddering ? I have no slipping at any rpm or gear, but if I change gears aggressively during strong acceleration the change is very rough and and hard sending a jolt though the car. I've also assumed this is due to my lack of skills in shifting fast.

Appreciate any and every help! Driving me and my passengers nuts :(

Thanks!!

Replace the spark plugs? Commonly causes issues

Replace the spark plugs? Commonly causes issues

Thanks for the response Hayden.

The car is on lpg so I fitted iridiumIX plugs that are ncolder by one degree and shorter gapped by 0.1mm than normal plugs for petrol based magna's. Been no issues with them on lpg but they were fitted over 40,000kms ago so are fairly used now. They are musky brown which is normal for a used plug.

That being said, it doesn't feel like a engine issue but a drivetrain issue. If anything would be wrong with the spark system it'd be the ngk leads that are just a bit too short for the plug holes and the cables have stretched a bit.

Also to ad to this, I quite often get small vibrations through the steering wheel. Seems to be strongest at higher speeds.

Could be a leads issue, especially being on LPG.

Does the shuddering occur when you take of normal? What happens when you let it out a little faster ?

Not sure if its relevant but when the car is warm and its turned off and on again, it has a very low rpm rough idle. Cold idle has a cyclic/repetitive hissing noise. Power seems down under 2400rpm.


Done a compression test?

Thanks guys for your responses.


Could be a leads issue, especially being on LPG.

Might be. I'm going to hook back my original leads and see if the problem dissipates.


Does the shuddering occur when you take of normal? What happens when you let it out a little faster ?

Just checked it tonight. Can confirm it happens when I accelerate harder. If I launch slowly and easily there's almost no shudder. Maybe it is engine after all.
Not sure if it's relevant, but generally I'm finding that the car jerks a bit harsher when you back off the accelerator (even gently) and feels like it has been unsettled when you pull out. There is also a small knock when I pull back the accelerator (that could just be some loose plastic however).

Perry do you think you might know the problem?

Done a compression test?

Well, have you? lol
Definitely engine related.

Maybe distributor issue?

I like these guessing games lol
Serioiusly, you need to check the basics - compression, distributor cap and rotor, spark plug leads for a dud - high resistance - one, spark plugs for consistent appearance, air leaks after the MAF, and so on.

Done a compression test?


Well, have you? lol
Definitely engine related.

Thanks Max.

I was certain that this is a drivetrain issue because I recently lowered my car and at 160km+ things are getting worn down. (track days don't help!)

I'll start looking back to the engine to see if I can find the culprit.

Have not done a compression test, but a vacuum test instead. Results were positive with mostly steady reading at 20. No unusual behaviour noticed. Will look into compression testing each cyclinder for any differences across the block.


I like these guessing games lol
Serioiusly, you need to check the basics - compression, distributor cap and rotor, spark plug leads for a dud - high resistance - one, spark plugs for consistent appearance, air leaks after the MAF, and so on.

I'll run through the basics on the car to rule them out as I go.
- Compression: TBA
- Distributor cap & rotor: replaced with 2nd hand one around 15,000kms ago due to being caked in oil. Recent check of rotor and cap was good. No rust/damage found. Unable to check under rotor.
- Spark plug leads: NGK ones fitted 10,000kms ago. Cables bit short. Have been stretched slightly to fit. I have many spare old genuine ones lying around so will fit them again and see if there's any difference. Worth pulling out the multimeter?
- Spark plugs all look pretty normal for one that been used for a bit. Brown musky colour. No burnt stems or oil buildups.
- Air leaks are a big thing I need to check. Not having a smoke machine or knowing a cigar smoker makes this hard. Not very confident using the old trick of carby cleaner with hot engine parts.

Anything else to check?

If you stretched the leads slightly, maybe some damage to the insulation causing some cross firing under load, since it seems worse under heavy acceleration.
My old XD did that. Near pulled my hair out over that one, since they were brand new and tested fine.

I'd be swapping out those stretched ignition leads. Doesn't take much to break the conductor.
If you want to test them, use a multimeter, but stretch the leads - just pull on the ends - when you measure resistance. Should show up any that have broken conductors.
As for cross firing - have a look under the bonnet on a dark night, and give the engine a bit of a rev.

Easy way to check the ignition leads is to go to a place of total darkenss, open the bonnet and start the engine. Rev it and observe. If there is any breakown of the leads, it shows up really well.

Easy way to check the ignition leads is to go to a place of total darkenss, open the bonnet and start the engine. Rev it and observe. If there is any breakown of the leads, it shows up really well.

Don't just look at sparking between the leads, also look at the leads sparking across to any metal parts, and look for sparking on the distributor cap.

I bet it is the NGK leads though, worst thing you can do with leads, having to stress them just to make them fit.

Even disturbing the leads eg to replace a rocker cover gasket can stuff them. This is even more so when using gas. I have found that the Manga is not as sensitive to HT leads as the Pajero, because the Magna uses 7 mm insulation compared to the Pajero's 5 mm dia. They are skinny and sensitive. When routing the leads (new or old) try to avoid having them near any metal parts on the engine, and try to avoid having them cross or touch each other. In particular, the Pajero is sensitive to cross firing (from one lead to another). When this happens, if the inlet valve on one cylinder is open, you get a massive backfire (not funny because the air cleaner box gets blown apart). It takes time to route the leads properly, but is worth it.

Thanks guys for all your help! Great stuff!

I'll endeavour to run my car at night and see if there's any unexpected sparking going on under the hood. Never though that the leads could crossfire with insulation on.
The ngk leads are just that much too short so the leads are tightly against the rocker cover. Getting then out of the plug holes is also very difficult without removing them from the dizzy.

Have got a new set quoted at $160 from Mitsy. 3x the price of ngks :(

That being said, surely a lead problem would cause power loss at any rpm? Once I get past 4000rpm, hard launch or not, there is no shuddering. Also there's a lot of power past there too.

So to update this conundrum, I've now replaced the spark plug leads with the ones my car came with. Unfortunately, while I do like the better responsiveness and elimination of a rough idle, the car still does shudder during acceleration.

I can now confirm that shuddering is not related to how hard the car accelerates. Basically, if the rev range reaches between 3200rpm to 4800rpm the car with shudder and you can hear all the trims and panels in the car shake. Inspection of the engine from above has come up dry for any potential reason for the shudder.

Any other suggestions?

harmonic balancer?. that's all ive got, the rest have been said

Not the leads then.
Checked obvious things like the engine mounts and CV shafts?
Does it develop the shakes if you slowly take the revs up into that rev range when in neutral?
Consider taking the car to a mechanic to eyeball things.

Thanks again everyone for the prompt replies and assistance!


harmonic balancer?. that's all ive got, the rest have been said

I've been wondering if it might be the culprit. Its never been changed but its fairly rare they go bung. Not really sure on how to check the condition of the balancer. They are usually pretty expensive to buy so I'd really want to make sure that would be the cause before forking out the cash for it.

Although the harmonic balancer was used to turn the crankshaft when I did the manual conversion and subsequent gearbox replacement later on. Maybe the bolt got loose and the effects of it are now being seen 20,000kms later. Tighening will be difficult. I think I'll need to buy a tool for it or try and stop the flywheel from turning.



Not the leads then.
Checked obvious things like the engine mounts and CV shafts?
Does it develop the shakes if you slowly take the revs up into that rev range when in neutral?
Consider taking the car to a mechanic to eyeball things.

It can't be the driveshafts or engine mounts as I've replaced three of the four engine mounts less than 2000kms ago with MacKay mounts. Remaining factory gearbox mount is not broken but a little worn. I'll need to replace it but I'd be very surprised if that was the cause. Did not look bad enough to me to rule it would be at fault.
Both driveshafts have now been replaced. Drivers side 20,000km ago and passenger side last week using brand new aftermarket shafts. While they're not genuine they have new CV joints and used driveshaft. I did need to tap the CV joint to get it into the gearbox.

I'm wondering if the steering rack/power steering system could cause the issue? I get minor vibrations through the wheel despite wheels being balanced & aligned recently and the tie rods both have been replaced. Also there's a good 15-20 degree freeplay and the wheel needs to be turned slightly toward the right for the car to drive straight.

Il have to prop the car up and check all bolts and then the wheel bearings.
Considering maybe even the control arm ball joints could be givng me grief. No boots are busted though. How can I check if they're functioning correctly?

Shuddering does not occur in neutral as far as I remember.


Appreciate any help!

No shuddering in neutral huh? I suppose releasing the clutch also removes the shuddering?

No shuddering in neutral huh? I suppose releasing the clutch also removes the shuddering?

Can't say I can confirm this because I've not pushed down the clutch during acceleration. That being said, testing the car by pushing the clutch down during acceleration may not still assist in diagnosing the problem because once the clutch is disengaged; no power & load is being transferred to the driveline.

I'm beginning to look at the clutch and driveline being the problem, especially considering it only occurs when the car is under load (i.e. accelerating). My intermediate shaft bearing carrier/mount had to be modified to fit to my 3.5l as it was removed from a 3L. The 3L bearing was removed and pressed into the 3.5L shaft mount. I'm thinking the bearing may not functioning smoothly. Local wreckers has a 3.5L manual in stock so I will pick off the bearing & mount off on the weekend and fit it to my car.

If that doesn't fix it, the car is going to have to see a professional suspension specialist for them to inspect the bearings and bushings because I can't spot a fault.

Otherwise, worse comes to worse, the gearbox may need to be taken off to inspect the clutch and flywheel. It may just be the cause of the shudder. However, there is no clutch slip and the car does change and grip in gears well - even under load.

Any objections/suggestions to my thinking about isolating the problem?

Also, on a side note, do pressure plates "wear out" ? i.e. Do their effectiveness decrease with time. Is using a second hand one a bad idea?

Pressure plate can wear, the fingers can bend or break and the thrust bearing can wear the fingers away. That being said I personally haven't seen that happen to a pull type clutch like in the magna.

Pressure plate can wear, the fingers can bend or break and the thrust bearing can wear the fingers away. That being said I personally haven't seen that happen to a pull type clutch like in the magna.

Thanks for the input mate!

I remember when I fitted my second gearbox, that during the struggles to get the gearbox to line up to the engine, the input shaft on the gearbox bumped into the pressure plate dampening springs and broke the inner spring/circlip. I put the gearbox on and since I had no clutch slippage or harsh gears I figured all is well with the pressure plate and clutch.

Maybe after all, this could be the isuse? I was thinking of maybe replacing the pressure plate with a second hand one. If the cluth and flywheel is fine then I might just need a pressure plate. Local wreckers have 3 manual cars - one with 140km, anouther with 180km and 3rd with 280km. The 3rd one would have to have had a clutch change at some point but the question is when. I imagine the first two have probably never had one changed (maybe why 140km one looks unscathed in wreckers).
Might be worth getting a price for a brand new one first.

So, I spent many long & hard hours last weekend replacing the bearing between the intermediate shaft & driveshaft and the shudder has not disappeared.
Bearing was shot though, so it was worth replacing.

But after tightening the driveshaft, I think I may have found the problem; my drivers side wheel bearing. There's definitely free play in the wheel, even though the driveshaft & wheel nuts are tight.
My first thoughts are the wheel bearing, but I'm thinking the ball joint might be stuffed. How would I know the difference between if the ball joint or bearing is buggered?

I don't have a press, so I'd have to try and push out the bearing using hammers & other tools. Thinking I might be better off just buying a new hub assembly? Anyone know the price difference between them?
Bursons sell a bearing kit for $100, but not sure on their price for a hub assembly. Rockauto is quite expensive for a bearing assembly at $200+shipping. Bearing is only $60 incl shipping off there.

How would I know the difference between if the ball joint or bearing is buggered?


Get the wheel off the ground, and wriggle the wheel horizontally and vertically. Look where the play is. Look at the ball joint itself, and where the disc meets the caliper. Going to be obvious if either is worn.

Replacing either (or both) will require a press or new components.

Hi MagnaP.I,

I take it you've since gotten rid of your Magna. Did you ever get to the bottom of this issue? I've bought a cheap TH Sports that's having exactly the same issue.

I've replaced the 3 main engine mounts, as well as plugs and leads. The replaced mounts helped limit the vibration, but not eliminate it. Now I'm thinking it might be a CV or shaft issue. Seems to happen more when the right-front hand side of the suspension is loaded up - when turning left and accelerating, for example.

Cheers,
Daniel