So after chasing around what could be causing my car to have rough acceleration between 1500 and 2300 rpm and getting no where I took it to the mechanic.:confused:

They've had it for two days and can't figure it out either. They tell me that there's nothing wrong with they way the engine's running and that what I'm feeling is a vibration rather than a misfire. New leads and plugs haven't helped. They say they've driven the car a lot and given it a thorough examination and can't tell what is causing it.:cry:

The same mechs fitted new CV shafts for me about three weeks ago. Two days later this rough acceleration problem started. I trust these guys on their workmanship however - they are a CV shaft specialist. I raised the possibility of it being CV shaft related but am inclined to agree with them when they say it's just not logical that they would cause vibration under load from 1500-2300 rpm and them be smooth as silk at highway speeds and faster.:confused:

So I'm stumped. Does anyone have any suggestions. Would analysis by Mitsubishi on one of their special machines be worthwhile? Or just an expensive waste of time?

Just throwing it up here, But engine mounts???

the older the engine mounts the more they sag - if not broken leave them

if the cvs have been changed - try changing the tyres from the back to the front

you are supposed to get a wheel alignement after a CV change

balance the tyres

have the wheel alignment place check the lower control arm bushes and ball joints

What about injectors causing it to not inject the fuel propley ( can't think of the word) , because I've had the same problem for the last 2 years and no one has had any idea, until last week when i finally changed the fuel filter because it started to use more and more petrol. and anyway put injector cleaner through it, it helped a bit. I've done the same as you mate and thats the only thing that left to do. it will go away for a bit if you go for a spirited drive out the road if you know what i mean :D

it will go away for a bit if you go for a spirited drive out the road if you know what i mean :D


I noticed this on the first day it started misbehaving. I took it out for a thrash and it performed faultlessly :badgrin: . Later back in regular driving it has this roughness again at low revs.:cry:

The mounts have been checked and ruled out by the mechanic.

Good points about wheels and balance magna buff, but like I said the vibration/roughness is only in that small rev range. Curious and annoying.

I'm thinking maybe fuel pressure and or clogged injectors? I put a whole bottle of injector cleaner through it a week ago. made no difference. I always run on premium anyway which I understand has more cleaners in it or something.

Another thing. Motors are generally a bit rougher in the low rev range under load and vibrate a little bit (like when slogging in a too high gear). I wonder if this is enough to trigger off a sympatetic vibration in the running gear (wheels, CVs) which smooths out when the engine enters higher revs.

it still wouldn't hurt to get you injectors clean propley, I'm getting mine done after Christmas + you will probley get better fuel economy

Are the drive shafts new or reconditioned? Your mechanic tells you that it is vibration you feel.
Before changing drive shafts you did not have this problem you have now. Problem noticed two days after drive shafts have been changed.
I have strong feeling that one of the drive shafts or dodgy workmanship is causing your problem.
Did you hit kerb or pothole, or have punctured tyre repaired and not balanced after drive shaft job, before noticing rough acceleration?
I bet you didn't.
It is possible that balance weight fell of one of your wheels and made it unbalanced. To rule that out have all your wheels balanced and rotated.
Logic is kinda weird stuff occasionally. It is possible for something which rotate that cause vibrations at certain revs and be quite ok at higher or lower revs. To rule out drive shafts, is to change one, and if problem still there change the other one as well. Doubt your mechanic will be wiling to do that. You might agree to pay for labour if problem after doing this still exist.

It may be just me, but I don't trust mechanics.

The shafts are reco units and i have the impression there's more vibration turning right than left (loading up the left hand shaft?)

The mechanic indicated to me that he would be willing to change out the shafts if I wanted him too, though he didn't think it would fix it. I told him I'd get back to him after the holidays and after I'd taken more advice (i.e. asking you guys).

Hmm, a little web surfing:

http://www.aa1car.com/library/2004/bf100434.htm
A shudder or vibration when accelerating. May be caused by play in the inboard or outboard joints, but the most likely cause is a worn inboard plunge joint. Similar vibrations can also be caused by a bad intermediate shaft bearing on transaxles with equal length halfshafts, or by bad motor mounts on FWD vehicles with transverse-mounted engines.

http://www.geraldstires.com/Services/CV/cvjoints.htm
To check for a bad inner CV joint drive your car up to 40-50mph and note if there are any vibrations during the acceleration process. If there is, remove your foot from the accelerator and then note if vibrations disappear. if they do, then you probably have a bad CV joint.

ok is the vibration at any speed as long as the engine is within that rev range?

also does the vibration get worse at full throttle or on deceleration?

Is the vibration only related to engine RPM?

got a few ideas but need to know these things first to rule out other possibilities.

Vibration is only under moderate to firm acceleration in the 1500-2300 rpm range

Does not vibrate on deceleration or at cruise. For instance at 2200rpm cruising on the highway there is no vibration.

just some ideas

what are the cylinder compressions--

anyone would think the bottom end has spun a bearing either conrod or mains

the other unusall one is the timing pully has become oil soaked
and somehow shifted on its rubber ring shifting the timing point

possible flywheel damage or wear on the clutch itself

the rev range is the guide to the problem

tyre balancing is only done at one speed and not under load its not a cure for all speeds

still thinking

you are supposed to get a wheel alignement after a CV change


Just wondering why this would be the case?

just some ideas

what are the cylinder compressions--

anyone would think the bottom end has spun a bearing either conrod or mains

the other unusall one is the timing pully has become oil soaked
and somehow shifted on its rubber ring shifting the timing point

possible flywheel damage or wear on the clutch itself

the rev range is the guide to the problem

tyre balancing is only done at one speed and not under load its not a cure for all speeds

still thinking

Uneven cylinder compression is a good posibility.

You'd know about a spun bearing if you had one, and so would your mechanic.

Shifting the timing point on the crank pulley wont change the way the engine reads TDC, so it wont affect firing conditions.

Clutch or flywheel damage would be very noticeable as the RPMs rise.. the higher the RPM the more noise/vibration it'd make.

Another one is an exhaust component fouling on the car body. As the exhaust resonance increases it transfers vibration throughout the car.

The most likely scenario is either soft/broken engine or trans mount or worn CV.. and seeing as how the rev range you describe, is the range where harmonic imbalance is commonly felt at; i'd say the engine mounts are somewhat amplifying the feeling.

Still.. its hard to diagnose stuff without actually seeing the car doing its thing.
Hope ya get it all sorted soon.

Quote:
Originally Posted by magna buff
you are supposed to get a wheel alignement after a CV change

Just wondering why this would be the case?


Because you usually need to disconnect the tie rod and the ball joint from the steering knuckle.

Quote:
Originally Posted by magna buff
you are supposed to get a wheel alignement after a CV change

Just wondering why this would be the case?


Because you usually need to disconnect the tie rod and the ball joint from the steering knuckle.

Not on a magna, all you need to do is disconnect the bottom ball joint.

just as a test, open your bonnet then load up the engine in both forward and reverse, get someone to watch how far the engine moves, it shouldn't move any more than a few inches. any more and you got a broken engine mount. sometimes it's hard to pick up this sort of problem just by looking at the mounts themselfs.

i can tell you now it's not a wheel/tyre problem.

Also take it to an exhaust shop and tell them the problem you have as it may be a broken bracket on the engine pipe.

Gee thanks for all the replies - you guys are all tops.

I've been for a long drive in the car today and can confirm that the vibration only happens under acceleration at the aforementioned rpms - all other driving is sweet and smooth. Have done 100km of highway today and the car is perfectly smooth.

The mechanic told me (I didn't ask him) that the engine mounts are fine.

Having the exhaust checked is one idea - I suppose, as is having a compression check.

The whole thing is bumming me out. Have to learn to be a bit more zen about it all - eh?

Problem now fixed. See:
http://www.aussiemagna.com/forums/showthread.php?t=55894

Whens it vibrating? whilst driving or whilst stopped?


Its the Auto transmission - torque convertor


Whats your car idle on in Drive when at the lights? (off-topic)


You will notice if you up the idle slightly it might go away, but the small vibration will remain, if at lights, if you apply the brakes full it will idle yuck, if you do it soft it goes away a little.

Actually, the problem is not fixed. The vibrations are still there, greatly reduced but still quite noticeable.

May have to take severe action (reaches for shotgun).

my tr has exactly the same problem in exactly the same rev range.

when it vibrates, does it come up through the brake pedal? everything shudders on mine.

im putting it down to a cv related problem. when the car is cold and i get near full lock, i get a massive squeal - although the boots arent broken, and in warmer weather its fine. still get massive vibrations in that rev range!

I feel it in the accelerator pedal and in the seat.

I still reckon its the torque convertor, however a few things worth doing to reduce this is clean your TB and TPS (You will find the TPS has gunk so its not making clean contact when it swings side to side)

At the lights have your foot only softly on the brake, not pushed right hard down (Note leave a good gap between you and the front vehicle)

Make sure your idle is around the 700 - 800 range in Drive paused at the lights.

My idle has improved heaps.

Thanks Russian but my 5 speed manual gearbox doesn't have a torque converter!!! lol

Good tip on the TPS, and I will follow up on that, but no, I don't have idle problems in this car. It's vibrating when I accelerate.

Hi there TR 3000

Well it seems that this thread has been quiet since Feb hey? Is your problem sorted or are you still experiencing the vibration? Are there any other drivers experiencing this problem?

It just so happens that I am experiencing a similar problem. I own a KR Verada Wagon, 190,000km total. This car has had a some misfire problems over the last year as well as the vibration problem. When I am driving on a long trip on the highway the car starts to vibrate/shudder under load i.e. when accelerating from 90kms to 110kms+ and then when I back off on the throttle/coast along at 100kms, the vibration dies down. Also, sometimes it is worse than others depending on how long I have been driving, etc.

At first I was thinking that it was a misfire problem and I have since replaced the dizzy cap, rotor button and idle speed control motor. Ran it on premium V Power juice and performance was better but vibrations still there. :confused:

Had a mechanic drive it (to feel the problem) and he told me to get it in for a balance, alignment and check cv/driveshaft, which I think is my next step but after reading your post I think it could be something else. Any progress with your problem?

Anyone else got any clues on what this might be? I have checked engine mounts as well and they seem fine.

Only just saw your post but thought I'd throw in an answer anyway.

My problem has been mostly cured by refitting the original springs into the suspension. This reduced the vibrations about 95%, though I can still feel a slight flutter accelerating in second gear.

Here's what I think happened:

I had the car lowered with lovells springs but soon after it started vibrating. I think that the shock absorber-like roll insulator under the rear engine mount gave way inside and allowed the engine to rock back on acceleration thereby shortening the range of travel inside the CV shafts causing them to bottom out.

At the time visual inspection showed all the engine mounts to look fine, but the rear mount itself has deteriorated quickly since then showing splits etc. Sagged or worn engine mounts can let the whole motor droop in the bay, also shortening the play in the CV shafts.

I am hopeful that when I get all the mounts replaced (psyching myself up for this) I may finally nail the last vestiges of vibration and even go back to the lowered springs at some tome (I drove brilliantly). I also hope it will make the car nicer to drive altogether.

Still have to get onto finding a place that sells quality mounts at a bargain price!