Engine Wobble

[Matrixabc]

Hi All,

I recently replaced the spark plugs on my 2001 LS430, I now notice a slight "wobble" when the engine is at idle, by wobble I mean the whole car feels like it shakes (intermittently), you can only just feel it but its there, I have had a same on all the V8's I have owned, but usually they say you should change the plugs to fix it.

I got the plugs (Denso iridium) off eBay (£25.00 for 8) they were guaranteed as genuine, and had been bought in bulk and shipped with out boxes. I checked on the Denso site to see what fakes look like and they appear to be genuine.

I would assume if I had a misfire of any emission problem then the check engine light would come on, and the codes stored.

the fuel economy is still around 22mpg (tank average) even with a new air filter. but I have trouble driving economically I just love the feel of the torque pushing you into your seat.

what sort of MPG is every one else getting on there 430? and do you suffer or have suffered from engine wobble?

as i said above the wobble is very slight ( the wife thinks I'm imagining it ). and to be honest I'm not sure if it was there before, as It has taken me a while to adjust to the new driving experience.but as every thing else is near perfect I wonder of one if the plugs could be duff? but how would you check them? (other than a resistance or megger test)

regards

Alex.

[SteveW37]

Hi

22mpg would seem about right think computer says mine is 22.7.

No trace of engine 'wobble' though.

My girlfriend's car (Renault Megane) does this and revs seem unsteady at idle, don't think you should be experiencing this with a Lexus.

[Oracle]

did you change the spark plug wires at the same time?

if not you may have damaged one of them - which will cause a lumpy idle.

[Haylands]

Hi

My LS430 does about 22-23mpg as well, if there is a missfire the check engine light will come on, and codes will be stored, most garages now have OBD11 readers and for a small fee will check for any faults stored, the system also stores latent faults as well so you can be confident if it is all clear.

The LS430 doesn't have plug leads as such it has a coil for each sparkplug which is part of the plug cap.

Did you torque down the plugs properly you have to crush the washer to ensure a proper seal and tighten to the correct torque or you will get an air leak, but this should also show up and bring on the check engine light....

Let us know what happens

Pete

[Matrixabc]

hi all,

I only notice it when it is first started and until it is fully warmed up, I quite often do stop start driving and cant remember noticing it when its hot. the only other thing I have noticed but may be totally unrelated, is some time when accelerating it is not smooth it can be a bit jerky, "surging" and also when cold around 40-50 on flat road with slight throttle the car stammers, but I have had this on An A8 3.7V8 . and this may be related to the gear box being between gears, where it is undecided which gear to be in.

the original plugs were NGK's

I did struggle to get the plugs tight as you have very restricted access to them, I may need to spend another afternoon checking them.

as mentioned above they do not have leads or a distributor, the have the coil pack directly on the plug, and if there were any fault the check engine light would come up. I just recently sold my ODB11 reader leads as they had been unused for he last two years while I have been driving a Lexus..

Regards

Alex.

[Haylands]

Alex

How many miles has it done?

What petrol do you use?

If highish miles or you use ordinary, cheap supermarket petrol you may need to use some injector cleaner.

Little known fact.... don't use more than one dose per oil change as it thins the oil and can cause damage if used repeatedly

And whereabouts in the southwest are you as I'm down that way the week after next and could meet you and compare engines..... (this is getting slightly anorakie now!!!)

Pete

[maneesh]

did you change the spark plug wires at the same time?

if not you may have damaged one of them - which will cause a lumpy idle.

I agree with Oracle. Sounds like one of the wires could have been damaged. Have a check of each of them to check the resistance levels.

Plus, I read somewhere that plug wires should be changed at some point too according to age and mileage.

[Haylands]

did you change the spark plug wires at the same time?

if not you may have damaged one of them - which will cause a lumpy idle.

I agree with Oracle. Sounds like one of the wires could have been damaged. Have a check of each of them to check the resistance levels.

Plus, I read somewhere that plug wires should be changed at some point too according to age and mileage.

Maneesh

The 430 doesn't have plug leads it has a coil on top of each plug....

Pete

[Matrixabc]

Its only done 62K, and Ive just put some injector cleaner through it, which did not seem to make any difference.

another guy on here with a GS430 PM'd me to say he has exactly the same symptoms..the common denominator seems to be a recent change of spark plugs.

I need to check them to make sure there tight and see if they all look the same.

I guess it could be any one of the many sensors controlling the ignition system that could be slightly out of calibration. as it only seems to be there until it has reached full working temperature.

I'm in Stroud.. 10 mins off the M5

[Haylands]

Alex

Just a shot in the dark here..... Could it be that when Lexus change plugs, they do it during a service when the Battery will be disconnected and the ECU will lose its memory, then have to relearn when connected and so learn whatever it needs to, to compensate for new plugs???? If that makes sense. I know the gearbox ECU learns your driving style, maybe the engine ECU adapts for worn plugs and then needs re-setting when you change them.

I could of course be talking out of my arse but maybe worth disconnecting the Battery for 30 mins and see what happens.... don't forget to reset your seat memory when you reconnect it or you will lose it.

Pete

[bazgtr]

Alex

Just a shot in the dark here..... Could it be that when Lexus change plugs, they do it during a service when the battery will be disconnected and the ECU will lose its memory, then have to relearn when connected and so learn whatever it needs to, to compensate for new plugs???? If that makes sense. I know the gearbox ECU learns your driving style, maybe the engine ECU adapts for worn plugs and then needs re-setting when you change them.

I could of course be talking out of my arse but maybe worth disconnecting the battery for 30 mins and see what happens.... don't forget to reset your seat memory when you reconnect it or you will lose it.

Pete

I state this many times with a V8 and the LS versions.

Change the plugs,leads,rotor arms and distrubitor caps and that makes a whole world of difference to the car.

These items should be around £100-£150 all in. You'll have to fit them yourself which is not too hard. Loads of online information on how to do it.

Doing this way first will save you pounds in the long run in trying to find a miss on the car or another problem which might be there. Get rid of the obivious first.

[Haylands]

Alex

Just a shot in the dark here..... Could it be that when Lexus change plugs, they do it during a service when the battery will be disconnected and the ECU will lose its memory, then have to relearn when connected and so learn whatever it needs to, to compensate for new plugs???? If that makes sense. I know the gearbox ECU learns your driving style, maybe the engine ECU adapts for worn plugs and then needs re-setting when you change them.

I could of course be talking out of my arse but maybe worth disconnecting the battery for 30 mins and see what happens.... don't forget to reset your seat memory when you reconnect it or you will lose it.

Pete

I state this many times with a V8 and the LS versions.

Change the plugs,leads,rotor arms and distrubitor caps and that makes a whole world of difference to the car.

These items should be around £100-£150 all in. You'll have to fit them yourself which is not too hard. Loads of online information on how to do it.

Doing this way first will save you pounds in the long run in trying to find a miss on the car or another problem which might be there. Get rid of the obivious first.

Baz

This is a 430 it hasn't got plug leads , well not high tension ones anyway, it doesn't have a distributor, so no cap or rotor arm, they have a coil on top of each plug and the ECU controls when each plug fires, this has done away with the troublesome part of the high tension circuit, the coil packs do fail but this is easy to find as the computer will store the fault code, Alex has problems with a lumpy engine AFTER he changed the plugs.....

Pete

[JellyBean]

I once unwrapped a brand new set of plugs, gapped them correctly, fitted them and had a misfire. After a lot of head-scratching and messing about, I discovered one of the plugs was duff.

Just a thought...

[Mike_B]

Its only done 62K, and Ive just put some injector cleaner through it, which did not seem to make any difference.

another guy on here with a GS430 PM'd me to say he has exactly the same symptoms..the common denominator seems to be a recent change of spark plugs.

I need to check them to make sure there tight and see if they all look the same.

I guess it could be any one of the many sensors controlling the ignition system that could be slightly out of calibration. as it only seems to be there until it has reached full working temperature.

That's interesting - it wasn't me that PM'd but I also have a GS430, and I also have these symptoms. I have noticed that if I turn the AC on, the problem disappears completely - the idle revs rise slightly to compensate for the drag of the compressor. I don't know what it was like before the plugs were changed, as I picked it up with ca. 50k miles on the clock, but the dealer performed the 60k/6-year service which included new plugs and a host of other bits and pieces.

I had put it down to the idle speed being ever so slightly too low for smooth running. I will try the suggestion of injector cleaner and see how it goes... It really is very subtle, but it's definitely there.

[Matrixabc]

It is almost undetectable, but once you notice it you become aware of it. it could be a plug that is not working 100%, if it was a misfire it would bring up a fault code.

I could try disconnecting the Battery, does the radio have a code?

[Mark W]

resetting ecu made absolutely no difference to mine.

also goes away (or less noticeable) when a/c on due to higher revs

if you drop in neutral does it get worse?

going to get the plugs changed next week-definitely thinking one is duff or not been fitted right.

if it fixes will report back

driving me nuts cause no one else (even a stealer) notices- but definitely there

[Mike_B]

also goes away (or less noticeable) when a/c on due to higher revs

if you drop in neutral does it get worse?

No, in fact it goes away if I put it into neutral - but then the revs rise because there is no drag on the torque converter any more. So I assume this achieves the same thing as putting on the AC.

Anyone know if it's possible to raise the engine idle speed without having to put the AC on?

[Mark W]

Have you tried leaving in "N" for several seconds - When I drop mine into N - revs rise for a time - then ECU must compensate as revs gradually drop back down again - its then I get the "wobble".

I wouldnt condone trying to atrificially raise the idle speed - For at least 2 reasons;

1) Increase on consumption

2) Theres probably a "fault" somewhere and I think doing that would just mask the problem. Which in turn prob means you are always running inefficiently - you just dont experience the wobble due to the increased revs and the frequency at which the fault is occuring.

[bazgtr]

Have you tried to put the old plugs in again to see if it goes? This will then confirm that the problem lays with the plugs.

[Haylands]

Hi

So this "wobble" happens when cold?

What engine speed is the rev counter showing when you get the wobble and how long has the engine been on?

And when you say it goes when you turn the a/c on, does that mean you turn off the a/c when you get out the day before?

Any other parameters to bear in mind?

Let me know the above and I'll see if mine is any different.

Pete

[Mike_B]

Hi

So this "wobble" happens when cold?

What engine speed is the rev counter showing when you get the wobble and how long has the engine been on?

And when you say it goes when you turn the a/c on, does that mean you turn off the a/c when you get out the day before?

Any other parameters to bear in mind?

Let me know the above and I'll see if mine is any different.

Pete

No, only when warm. If the engine is cold the idle speed is raised sufficiently to mask it.

About 600rpm, however on the GS the rev counter at the very bottom has condensed markings making it a little difficult to be accurate.

Usually I don't run the AC this time of year except to clear the screen etc. Also, since it only happens when warm, what I did the evening before I don't think matters especially. Engine has usually been running at least 15 minutes before I notice it, and then only when waiting at lights, queues etc.

The only thing to add is this - I only get it when the engine is idling at the lowest speed possible, ie Drive is engaged (pulling down revs), AC is off, and the cold-start rev booster is disengaged as the engine is warm. It's really very subtle - the closest thing I can think of is when you shut down a diesel engine, and the car shudders briefly. It's nowhere near as strong as that, but the sensation is the same. I think what's happening is the ECU is detecting the engine is running too slowly and fractionally increases revs for a second, then lets them drop again, so every couple of seconds you get a very slight wobble through the car... You don't see the rev counter leap up and down though, it's not that bad!

[Haylands]

Hi

So this "wobble" happens when cold?

What engine speed is the rev counter showing when you get the wobble and how long has the engine been on?

And when you say it goes when you turn the a/c on, does that mean you turn off the a/c when you get out the day before?

Any other parameters to bear in mind?

Let me know the above and I'll see if mine is any different.

Pete

No, only when warm. If the engine is cold the idle speed is raised sufficiently to mask it.

About 600rpm, however on the GS the rev counter at the very bottom has condensed markings making it a little difficult to be accurate.

Usually I don't run the AC this time of year except to clear the screen etc. Also, since it only happens when warm, what I did the evening before I don't think matters especially. Engine has usually been running at least 15 minutes before I notice it, and then only when waiting at lights, queues etc.

The only thing to add is this - I only get it when the engine is idling at the lowest speed possible, ie Drive is engaged (pulling down revs), AC is off, and the cold-start rev booster is disengaged as the engine is warm. It's really very subtle - the closest thing I can think of is when you shut down a diesel engine, and the car shudders briefly. It's nowhere near as strong as that, but the sensation is the same. I think what's happening is the ECU is detecting the engine is running too slowly and fractionally increases revs for a second, then lets them drop again, so every couple of seconds you get a very slight wobble through the car... You don't see the rev counter leap up and down though, it's not that bad!

Mike

What an excellent description of a symptom.... I know exactly what you mean, I'm off out in a bit I will try mine and report back

Pete

[Haylands]

Hi

Right, been out in mine, got it nice and hot, sat on the drive with it in gear with the front and rear aircon off and the tick over is around 600rpm, put aircon on and there is absolutely no difference in rpm, the needle does not even quiver, the engine note stays the same, tried it with front/back and both aircon on, although I don't think that will make much difference as its only got one compressor.

Put the car in neutral and the revs rise to about 850rpm, again try the aircon and there is no difference in rpm at all, switch it on and off and wait for the compressor to cut in and the revs stay the same....

Turn aircon to cold and check it works!!! and yes it does, check compressor and with my head under the bonnet I can hear the electric clutch on the compressor cut in so that is working...

Now back to the story, with the car ticking over at 600rpm I can just, and I mean just feel the wobble you are talking about, if you close your eyes to heighten the senses and sit perfectly still I can feel the diesel type shimmer, and my wife can feel it as well, it is incredibly slight and is rhythmic.

So now you have broken mine as well so I'm not playing any more........lol

Anyway, thoughts. I recon it’s something to do with the lambda cycling, at idle the pre cat lambdas cycle between rich and week and adjust the mixture accordingly and I recon what you feel is the Ecu changing the mixture slightly, this is probably getting more noticeable as our cars get a bit older and the rubber mounts start to harden a bit.

I tried it on petrol and LPG and it makes no difference. LPG needs a very good spark to ignite it as its flash point is twice that of petrol so any deteriation of the ignition system and you will notice it far more on LPG than you will on petrol.

So I recon it’s just one of those things and we will have to put up with it.

And by the way I know a guy who is an aircon mechanic and, although he doesn't want it to become common knowledge, he advises that you leave your aircon on all the time winter and summer, he asks every owner of every car he fixes and virtually all of them turn the aircon off because they think it saves petrol. Well it might save 0.1% of petrol but it costs loads to get it fixed when the seals have dried out and its sprung a leak.... anyway I haven't turned my aircon off in any car I have owner for the last 10years and I have never had an aircon leak and they have always worked...

So my 2p worth is stick the aircon on and forget about it

Pete

[terry moore]

Hi ,make sure u got the correct plugs.on the sides of the plugs there is a number which is the heat range. if u fit the wrong heat range,the car run fine ,but u lose the smoothness,the plug gap is also important.eg NGK BPR6EY WITH A GAP OF 1.1 B)

[Matrixabc]

I only really notice my "wobble" when you first start the car and its in Park.

the plugs I have fitted my self are SK20R11 and it says that you must not try to gap the plugs..