Hey guys,
So my 2001 Auto TJ Magna wagon has started to vibrate and it's driving me crazy. Started about 3 or 4 days ago with no previous signs of any vibration about to happen. It vibrates gently at about 60km/h and 2000 RPM and as you accelerate, it starts to shudder like crazy at about 120km/h on the highway.
I did some googling and everything points me to CV joints but I took it to the local mechanic to ask him and he reckons it could be the ignition leads. He said that it drops cylinders under load and it causes the vibration.
Has this happened to anyone and is this even possible?
I checked a few of the more easy to reach engine mounts and they don't seem loose but I can't get under the car for the time being.
I'm on a bit of a uni student budget so I can't really afford to replace the ignition leads if it is in fact the CV joints and vice versa so is there a way to test for worn CV's?
Really appreciate any help.
Cheers

It's interesting the mechanic is suggesting leads. For me an engine misfire or ignition breakdown would be associated also with a distinct loss of power I reckon. Since you've been driving it before and after have you noticed any performance loss?
Queston is, Is this a steering wheel shimmy, or a whole of chassis vibration ie the front end or is there a loss of power? Never easy to nail it over the web. I've had bad inner joints cause a lot of vibration but they came into play over 80kph.

I didn't even think of the power loss... There hasn't been a noticeable power loss but having said that, I've also tried to not load the engine to avoid the vibration in case it was a precursor of something really bad.
The vibration is like a chassis shudder, not so much through the steering wheel.
If it was CV joints, would it not still occur even while coasting because they'd still be rotating at whatever velocity?? Like if I back off at 110km/h on the freeway, aren't the CV joints still rotating so they should still vibrate?
Excuse my ignorance if that's wrong but I don't know much about how CV joints work :redface:

If it was CV joints, would it not still occur even while coasting because they'd still be rotating at whatever velocity?? Like if I back off at 110km/h on the freeway, aren't the CV joints still rotating so they should still vibrate?
Excuse my ignorance if that's wrong but I don't know much about how CV joints work :redface:

No, CV shudder normally occurs under load and will, for the most part, disappear when coasting.

I didn't even think of the power loss... There hasn't been a noticeable power loss but having said that, I've also tried to not load the engine to avoid the vibration in case it was a precursor of something really bad.
The vibration is like a chassis shudder, not so much through the steering wheel.
If it was CV joints, would it not still occur even while coasting because they'd still be rotating at whatever velocity?? Like if I back off at 110km/h on the freeway, aren't the CV joints still rotating so they should still vibrate?
Excuse my ignorance if that's wrong but I don't know much about how CV joints work :redface:

There's so many variables. I'm not going to stick my neck out on this one mainly because you say it's happened suddenly and you're feeling it at 60kph. I'd like to think a qualified mechanic would definitely know an engine misfire condition in which case maybe he's saying it is but that could be, coil, rotor, cap, plugs, leads. maybe ask if it's definitely ignition. Guess you don't know anyone handy with cars?

Just to share a recent misfire I had on an ASTRA. reknown for failed coipacks, ECUs, MAF sensors. I am totally paranoid about ECU failure. So I went arse about on this. I had a coilpack, swapped seemed fine on a quick trip, parked it and then several hours later jumped in and misfire, so ECU?. Next day, stuff around programming an ECU to match it, start car same misfire, PLUGS? yeah plugs quit, gap was huge. Did not know the service history looked ok but assumed.

If this happens at 60, I wonder what happens if you manually selected and hold 2nd. should be less load, higher engine RPM?

You'll get varied opinions on what happens with shafts and I can only use my Old galant as a reference. 80 and above horrible shaking not through wheel but whole front end literally felt like the whole drivetrain was bouncing up and down. On that vehicle lifting off most if not all vibration went. but the higher the speed and the more load on the drivetrain the worse it was and uphills it was absurd, changing back a gear reduce it slightly.

I never checked the inner joints on car , I just knew it was drivetrain, outer CV were fine no noise, it was logical in my mind inner joints.

I've read a few comments here with people saying they had bad inners and the vibration was still there coasting.

Also read of Torque Converter shudder. Only TC issue I've ever had was on a series 2 at TC lock-up and at 100 under light throttle, felt like engine disturbance , misfire under steady acceleration.

If the engine was misfiring so bad to cause the chassis to vibrate to unbearable, in my opinion you'd have little power to accelerate

my car was manual.

maybe get other opinions, family/friends take it for a spin

Sorry, a lot of waffle without any real help just my thoughts. very much sitting on the fence with this.

Easy way to check your HT leads - get yourself into a pitch black or very dark place, lift the bonnet and start the engine. You'll soon see if there is any breakdown either between the leads or to earth. Rev the engine or get someone to rev it for you and watch. If the leads are bad, you'll see a real fireworks display.

Easy way to check your HT leads - get yourself into a pitch black or very dark place, lift the bonnet and start the engine. You'll soon see if there is any breakdown either between the leads or to earth. Rev the engine or get someone to rev it for you and watch. If the leads are bad, you'll see a real fireworks display.

The only thing I'll add to this is not always. rear bank could be tricky but what if the breakdown is internal. That's what i had recently on my 6a12. breakdown was from the plastic plug tube to the head under the seal.

Cheapest way to check would be to get some leads from the wreckers and try them. Make sure the leads come from a car that has copped a decent hit, this should mean it was a runner.

The problem with HT leads is that they may be OK when they are in the car, but as soon as you disturb them, particularly if they are old, they may crack up then. Yes - the rear leads are hard to see, but if it is black enough, you will see something.

Many years ago, I had a Citroen DS21 injection. Magnificent car, but very touchy on the ignition. It would misfire regularly, and I would remove the plugs, regap them and put it back together. A day, week or whatever later more misfires.. Regap plugs.... You know the story. Finally it started misfiring as I drove into my driveway, so I stopped and lifted the bonnet, only to see on lead shorting to earth. What had happened was that I disturbed the leads to get to the plugs and that fixed the problem for a while. I was blaming the plugs when it was actually the leads which were wrong.

I had a set of TopGun leads in my NL Pajero. Biggest load of crap I have ever had. Checking them in the dark, I could see the leads firing all the way INSIDE the leads. Occasionally there was a short to earth, but more importantly, there was a short between leads. Example - if No 2 shorted whilst No 4 intake valve was open, a large backfire occurred, blowing the guts out of the airflow meter. Pajeros were different to teh Magna because they had only 5 mm HT leads whereas the Magna has 7 mm leads. For a while, I had Bosch leads on my wife's TF Magna and they were terrible. I chased that problem for a long time and eventually replaced the leads. That fixed it. NGK leads were the best I could find.

It vibrates gently at about 60km/h and 2000 RPM and as you accelerate, it starts to shudder like crazy at about 120km/h on the highway.
I did some googling and everything points me to CV joints but I took it to the local mechanic to ask him and he reckons it could be the ignition leads. He said that it drops cylinders under load and it causes the vibration.
Has this happened to anyone and is this even possible?
Sure is and, if that's what's happening you'd expect similar behaviour at around the same RPM is any gear under comparable loads.

is there a way to test for worn CV's?
The first thing to look for would be split CV boots. That's a pretty sure indication they're on their way out - because crud has been getting into them. Aside from that, a clicking sound from the CV-joint area as you go around corners (especially tight ones) is a good indicator.

<edit>. It vibrates gently at about 60km/h and 2000 RPM and as you accelerate, it starts to shudder like crazy at about 120km/h on the highway.<edit>

Just an observation 60 and 120 are harmonics, so makes me think it isn't electrical, much more likely mechanical.

120Km/h gives 4 Times the drag of 60 so if the load is a CV, or an engine or suspension mount it will be under much more load at 120, So it would get all the rubber engine/trannie mounts checked (not to hard for a mechanic on a lift) especially the drivers side engine mount. these mount can crack so they support everything just fine at low power, but under load the cracks open up and the metal mount parts vibrate.
If they check out look to the CV's - they usually don't both go at the same time so see if the vibration is worse on one side of the car or the other.

120Km/h gives 4 Times the drag of 60 so if the load is a CV, or an engine or suspension mount it will be under much more load at 120
Which is exactly why the effect of a misfiring cylinder would be all the more pronounced as speed increased, especially under accelerations as the OP says.

So far, I haven't seen a single post discrediting what the OP's mechanic said. Prima facie (because the mechanic likely knows his job and has inspected the car), faulty leads/plugs are the culprits and all this talk of other possibilities are mere distractions until the mechanic's advice has actually been tested instead of being speculated upon.

So I took my car to another mechanic and he said that it sounds like it's missing because it seems to happen under the same load and at about the same RPM. He said that it could be the spark plugs or the leads or a few things on the ignition side of things so I'm gonna take it to a dark place and see if there's any sparks when you rev it to check if it's the leads.
If it is the leads, is it a matter of buying a new set and changing them? Are they practically plug and play or is it much more involved?
I've tried to watch a few youtube vids but couldn't find much. And I also understand that the rear 3 are quite hard to get to so is it alright to change the front 3 and see if that solves it then if it does, just leave it be or will things be out of balance?
Thanks for all your quick replies too!

If it is the leads, is it a matter of buying a new set and changing them? Are they practically plug and play or is it much more involved?



If it really is a misfire, and not a worn, out of balance drive shaft, it is not certain if it is plugs or leads.
You haven't said how many km on the car, a misfire can also be caused by oil on the outside of the spark plugs from leaking tube seals.

The plug leads themselves are not cheap, I put a set on 2 days ago that cost me $80, a replacement set to keep as a spare set for my other Magna will cost me $100 imported from the USA, but I have no idea what a dealer would charge for the leads or putting them on.

"Plug and play" they are not, a lot of things to be removed out of the way first. The job took me 6 hours, but I tend to go slow and careful the first time I do a job.

You can pull out a couple of the front plug connectors to see if there is oil down there, won't cost you anything, and may tell you if the tube seals are leaking and causing the misfire (if it is a misfire).

You could also stick your head under the car and see if the rubber boots on the driveshafts are still intact.
Personally, I think you are jumping to conclusions thinking it is a misfire caused by bad plug leads.

(The new leads on my TL cured a misfire that was only evident when the car was first started from cold.
Your car's symptoms are totally different.)

I'm gonna take it to a dark place and see if there's any sparks when you rev it to check if it's the leads.
You might be lucky enough for that to show something, but simply revving the engine isn't going to put it under anything like the load it works under @ 60-120kph. Even if you can reproduce a misfire, seeing sparks is at most a confirmation of the advice you've been given; not seeing them doesn't negate it.

You might be lucky enough for that to show something, but simply revving the engine isn't going to put it under anything like the load it works under @ 60-120kph. Even if you can reproduce a misfire, seeing sparks is at most a confirmation of the advice you've been given; not seeing them doesn't negate it.

It's unusual for a misfire to occur at specific speeds, a misfire usually occurs at high engine loads, like accelerating heavily from a standstill.
Vibration at specific speeds is more likely to be mechanical.

It's unusual for a misfire to occur at specific speeds
No-one, including the OP has said it does. Indeed, the OP clearly said it becomes more noticeable as the speed increases.

In any event, the OP has now had two mechanics tell him essentially the same thing. Scouting around for opinions from people who haven't inspected the car just leads (no pun intended) to nothing more than pointless speculation.

Ok so I just pulled the forward ignition leads out of the spark plug wells and the right and left (looking at the car standing in front of it) had tiny bits of oil on them and the middle one brought up a heap, about 5mm deep of oil. Now obviously this isn't good and who knows what the rear 3 are like. I believe that means that oil is seeping through the valve cover gasket and into the spark plug wells?

You should get the rocker cover gaskets and sparkplug tube seals replaced while getting new leads put on. You will save on labour as the top half of the inlet manifold has to come off for both jobs. Genuine leads cost $140, are very nicely made and fit perfectly.

The problem sounds familiar to what I've experienced and I'd start by changing the spark plugs.

OP, get your mechanic to change the spark plugs, leads, rocker cover gaskets and tube seals.
It will cost a bit, and may not fix the problem.

(In case you don't already know:
The reason old cars are cheaper than new cars is because old cars need money spent on them to keep them in good running order.)

Alrighty, spark plugs it is. For now anyway... Anyone know if they'll be 16mm or 21mm plugs?
If this doesn't solve it, I'll have a go at replacing the rocker cover gasket and tube seals. Will I need a new intake manifold gasket? I've read some things saying it's a reusable metal one and others say it's not...?
Also, out of curiosity, for anyone that's had the rocker cover gasket changed by a mechanic, how much was it? I'm away from my mechanic for a week and I'm not sure if I'd be saving much by buying the parts and tools (torque wrench) and DIYing it.

As long as the intake manifold gasket dont get bent it will be OK to re-use. My mechanic charged me hour and half labour for back and front gaskets,tube seals etc.

Alrighty, spark plugs it is. For now anyway... Anyone know if they'll be 16mm or 21mm plugs?

From memory, the plugs are 16 mm. Certainly no the bigger size. I had 2 plug sockets - one with a rubber insert and the other without it. I used the rubber one to remove the plugs and hte other to reinstall them because otherwise the plug socket would get stuck down the tube.

Agree about the intake gasket. There are no water or oil lines in this area so the worst you can get is a slight air leak. If the gasket is flat, the leakage would be minimal and pose no problems.

I use a plug socket without the rubber insert to back off the spark plugs most of the way.
Then a 30 mm section of old fuel line gets lowered down the tube, it fits onto the end of the plug. Unwind and lift out.
Same bit of fuel line is used to lower the plug back down and start it off. Pull to pop it off the end of the plug. Torque wrench to 25 Nm.

Gaskets - including the throttle body to intake plenum - can be reused. Just make sure the mating surfaces of the gasket and the joint are clean.
Make sure you or the mechanic use a torque wrench to do up all bolts and nuts. 18 to 19 Nm for the 5 bolts and 2 nuts holding the upper intake to the lower, same for the 12 mm bolts across the back of the plenum chamber.

Don't lose the EGR gasket!

It's a bit of a job. Without replacing the rocker cover gaskets and tube seals the new plugs will just oil up again.

Cheapest, in terms of labour, to do the rocker covers, tube seals, spark plugs and leads all at once.

Another way to remove the loosened spark plugs from the tube is to simply reconnect a spark plug lead and pull them out.