LS430 2002 miss fire under load , revs limit

[Frostyboy123]

Hi team, pretty clued up with cars being a technician but I need your help.

 

serviced the car 3k ago genuine parts, car ran lovely and vastly increased fuel economy. One day joining the motorway uphill , the car acted like it had hit its rev limiter at around 3000 rpm, eased off and the car ran fine. Anytime you put it under load, rather than my usual tootling about it acts like its hit the rev limiter with a very very noticeable bang bang bang, not literally but the engines trying to rev but it won't like it hitting the Rev limiter but at lower revs. If you don't accelerate harshly it's fine , but under load not  help would be appreciated 

cheers 

[Bluesman]

I know there could be dozens of reasons why its misfiring but I had the same trouble with mine and it turned out to be an Oxygen sensor on Bank 2 I had a lot of other problems but that was the cause of all my heartache. Mike.

[Frostyboy123]

Like you say could be anything. She's done 342k but, can't help believing it's something that's failed, as it wasn't s build up to it ie. Getting gradually worse. 

[steve2006]

Any stored codes?

[Frostyboy123]

Nope, so it's mechanical, possible cause fuel rail pressure regs??

going to put my throttle body assembly in from my other ls430..... At least it eliminates that 

[TigerFish]

A faulty knock sensor can show symptoms like this.

Sent from my Iphone using Lexus OC

[Frostyboy123]

Going to swap the throttle body and TPS and throttle control first . Knock sensors under manifold, not a nice job. Easier to swap the throttle body off my other one first ...... Process of illimination 

[TigerFish]

Yeah, inlet manifold off for the knock sensor(s). Not that bad a job overall though.

Sent from my Iphone using Lexus OC

[Frostyboy123]

Ok fixed, 7.5 amp fuse EFI2 under bonnet popped, replaced drove great, then popped, and so on and so forth.....

 

checked wiring, heat shield just before cat bank2 no. 2 chaffed through the wiring causing earth....... Bent heat shield out of the way. Put silicone on the chaffed wire...... Happy days .....

[steve2006]

Nice work, diagnostics down to component level nice to hear that these days.

[Frostyboy123]

Old school mate, been at it 26 years all though I stopped being "on the spanners" many years back. I HATE not knowing why somethings not doing what it should, a simple "just put a new one on" won't suffice, I am a technician, not a fitter.

like you say though rare these days 

[runsgrateasanut]

Yawn!  4.25am - Mr Wu's gift to the World is disturbing my sleep as much as Brexit did

Found this thread and may help sort my Car problem. Same sort of scenario. Pulling away on kickdown or trying to overtake at 70mph on a Hill under load, car coughs and I fall back.  So could be chafing cable or Knock sensor. I wonder if the fault resurfaced after this. 

No fault codes.

Q.  I may be driving on Econ and perhaps I should be on Pwr.  Tend not to like seeing that damn green light on the screen. Could it be that the Car has a rev limiter when on Econ setting which affects Kickdown and top speed? 

Q.  Bank 2 is that Manifold side of the Cat/s or behind the Cat/s? Drivers or passenger side on LS400?

The Brain's not focusing too clearly right now.

[Malc]

I now run mine permanently on PWR and I think it improves mpg too 

Malc

[runsgrateasanut]

Just re-reading this thread.  7.5amp EF12 fuse blown.  Not too sure if same could apply to the LS400 ?  I found below thread but couldn't determine exactly what EF12 did or its location.

Can't believe I've been driving for six years with a blown fuse, but......be great if that is all my problem or highlights a Sensor issue.

Wonder if this thread can be moved to current issues.  I rarely look at the "specific Engine related" threads. Don't know why but am I alone on this? 

Hoping for a bit more info/help before I struggle to see under the Car or the fusebox.  Rupert? SOS please email me direct if you prefer. Thanks

https://www.bing.com/videos/search?q=lexus+ls430+fuse+ef12&view=detail&mid=AF48B16449E853FBE19BAF48B16449E853FBE19B&FORM=VIRE

 

[runsgrateasanut]

No EF12 fuse under the bonnet.

Will replace both upstream 02  sensors and found this which I'm hoping will match  the existing plate welded 02 sensor which for some reason Mk 2 Cars have, but only upstream, and thereby save me a shedload of money.  Amayama price for one €256.11 + postage + Import tax, etc..  Fortunately, I have two Toyota replacements from somewhere which cost less than £35 if I recall correctly.  Fingers crossed that the bolt holes match.  I'm emailing to get the measurements.

https://www.ebay.co.uk/itm/Oxygen-sensor-adaptor-for-toyota-mr2-celica-gt4-3SGTE-kit-car-hotrod-o2-lambda/372918667684?hash=item56d3af49a4:g:DJsAAOSwDnpeIuR3

[runsgrateasanut]

Update on previous

The plate added to rear sensors will fit as front sensors, but the plate is marginally thicker than an original part and so instead of using a Gasket my mechanic who will do the job next week use a smear of  Flue Fire Seal which is OK to temp up to 1500c. Fortunately,  I have some left over from the two Wood Burners (I don't burn wood) that I re-roped around the doors last year. It won't be on the thread of the Sensor. 

It will be interesting to examine the old sensors to find out if they are faulty or have been chafed.  27 years - is a lot of work for a part to suffer but no engine light ever appears when the Car stutters at speed.  Might replace the rears also. Makes sense. Can't test of course until who knows when?

 

 

[runsgrateasanut]

OK I don't mind spending money to replace parts I know are bad. 

This old thread also mentions "Knock Sensor".  

I copied and pasted this reply from someone on the US forum and would like to know if what is said applikes to the 1993 model.

Is there only one knock Sensor or two?   Would Lexus Dealership be able to link my Car to discover the fault whilst the Car engine is running? OBD1 system.   Or would it be purely a guessing game by the toyota trained people?  

Quote   You can change the knock sensors and wire harness without removing the intake manifold. Remove the EGR valve, PCV hose and you can get you hand into the V area of the block. A 27mm socket and small rachet with a flex head and the job is done.  Unquote

PS Car is running on 98RON when incident happens. New Petrol filter installed,

[steve2006]

It’s easy to do your own diagnostics on the older models Stuart, all you need is a bent paper clip and follow the instructions on the link. There are 2 knock sensors one on each bank which give codes 52/53/55.

Not sure about accessing via the EGR valve aperture but it’s very tight in there.

http://www.lexls.com/tutorials/intro/codereading.html

[runsgrateasanut]

Thanks Steve.

From what I've seen the Knock Sensors are front of the Starter Motor. One central and one on the RHS.  Not a fun job.

I have checked the OBD1 before and got no codes. However, just checked again and am getting a Code 25 lean fuel mixture code.

Can you clarify? The OBD box although showing on the internal diagram a grid of three boxes across (9 in first Box)  there are in fact six holes and not just three holes across. (18)  OK I have put the wire into E1 simple but Te1 is in the forth hole.  Wee bit confusing. Sure I did it correclty previously and got no codes. Could be intermittant. 

Perhaps changing my upstream O2 sensors this coming Tuesday will sort my problem or do I need to invest in a new or s/hand MAF Sensor.  I know the original can't be cleaned.    

[ColinBarber]

When were the O2 sensors last replaced? They can 'work' for a long time but should be replaced at least every 100k miles to ensure efficient running.

[runsgrateasanut]

That I can't tell you Colin.  I've put on about 35k since acquiring the Car six years ago.

Clutching at straws again, someone on another forum has mentioned the Fuel Pump Resistor to check resistance.  An NZ guy on the Tube has done some work on this part or by bypassing it shows increased flow of petrol.  Will check it out and make sure Air Filter is still as clean as last time I looked at it.  I think the resistor seems to affect cars at start up, so doesn't apply to my problem, but I'll still check its well earthed/connections etc. Under the MAF Sensor I believe.