LS430 Transmission Hesitation

[LEDMaestro101]

Hey all,

 Ok so I'm working through the list of troubles with my LS and I've come to the transmission or what I believe is a trans issue. A bit of background, when I bought the car it had very noticeable lag if you try and give it any more than 50-60% throttle, the lag would increase the more you try and floor it to the point where I'd be trying to join traffic, the car just wouldn't move and so (naturally) try and give it more gas by which time the gap in traffic has gone, I put foot on the brakes and the car surges forward from the lag. that has happened on too many occasions now. No error codes are thrown btw.

 So, I ran through 15 litres of ATF to clear out the old (black) fluid and it then topped up to the correct level as per the dipstick (the joys of the pre facelift!) but the symptoms are still present. The new fluid has helped dull down the feeling of the car upshifting (could never feel it downshift but always felt it upshift) but nothing else, still a hell of a lot of hesitation under any meaningful acceleration. This is my first LS so I don't have a base idea of how they are supposed to drive! it feels like it struggles to find a gear at times or when I put it into kick down, it shifts sequentially down through all the gears until it gets to 2nd (for example). I used to have an auto honda accord (literally the worst car I've ever owned) but that shifted straight from top to 2nd in an instant when put in kick down.

 The question, has anyone else experienced this? I've been reading a lot of posts about engine lag, cleaning MAF, TB, Air Filter engine coolant temp sensor etc but I've done those (and more) and nothing has helped. My next stop is the Pedal Position Sensor, I'm wondering if there is a dead zone in the Pot but I'm running out of money to throw at this car! If anyone has any thoughts/suggestions then please let me know. As a side note, might be unrelated but the engine is idling a bit rough, I've got spark plugs on my list to do but thought I'd add that bit of info in there just in case it's relevant.

Thanks

[Cotswold Pete]

I just had my plugs replaced, they were pretty mankey, and since then I have noticed that the foot to the floor pick up is better, though it was not as bad as you desrcibe, but I assume  this means I am getting a better fuel burn so better pickup.

Even with mankey plugs I was not getting rough idle, (tended to get idle hunting until I had throttle cleaned)., but maybe if you have one plug not firing right then might explain.

Only other thought is fuel pump not quite right, but I would have thought that would possibly throw up some error code to do with fuel feed.

 

[LEDMaestro101]

yeah I'm wondering if I have a bad plug. I think I'll have to pull a couple later on today and see what they are like. May have to get some new ones on order and replace them regardless. car has 113.000 miles on it but I'm unsure if the previous owner had the plugs changed (last service under their ownership was the end of 2017) so it'll be good maintenance and peace of mind if nothing else.

I discounted fuel pump a while ago for the same reason you mentioned, lack of error code, plus the car runs and drives fine and smooth apart from the acceleration issue haha. may be worth looking into though, if the new spark plugs don't help. Thanks for the insight!

[cruisermark]

hi

I am not sure wether you are aware but the LS430 has a weak spot where as coolant mixes with the ATF causing gearbox failure - this is due to the radiator design.

I would start by checking the colour of your coolant to rule out fluid contamination.

hope this gives some insight

[LEDMaestro101]

that was one of the first things I did with the car after I bought it oddly enough, I replaced the radiator with a new one and tried to flush out as much of the old fluid as possible (couldn't afford enough fluid to replace the entire system) but I've only recently been able to do a proper fluid replacement so at least now the ATF in the box is actually red! was coming out black to start with so I'm hoping no lasting damage was caused to the box itself.

[GrahamG]

When you say there is no error code for the transmission's bad behaviour is that from a full Techstream reading or just a cheap generic code reader?

Might it be worth a main dealer diagnostic check? 

[LEDMaestro101]

both, I originally read it on my reader (only showed an historical code for O2 sensor) and then had Lexus read it during a minor service a couple of months ago with the same results. Lexus couldn't diagnose the issue without me throwing money at them and then suggested replacing the transmission!

Just wondering if a faulty shift solenoid could be causing the issue. Just thinking back to when I replaced the radiator and put a bit of new fluid in the trans, the car threw up a P0773 (If I remember correctly). I then cleared the code, drove the car for about an hour and it hasn't come back since but it seems odd for it to show once and then not show again after several months.

[Cotswold Pete]

6 hours ago, LEDMaestro101 said:

 I put foot on the brakes and the car surges forward from the lag.

 

3 hours ago, LEDMaestro101 said:

Just wondering if a faulty shift solenoid could be causing the issue.

I am now thinking why would the LS surge forward.  Even if the soleniod was sticky, surely when braking your not pushes heaps of fuel into engine, so even if it does down shift (kick down) then surely the car would have engine braking, as you have effectively starved the engine if fuel and downshifted.

If you manually downshift then put pedal to the metal, do you get a different result, might give some clues as to what is not playing ball.  if that works fine, then that (hopefully) rules out plugs as major part of problem.

[LEDMaestro101]

I haven't been able to figure out the surge. I've had it since day one of ownership. so to give an example (and this happens every time) when parked up, I blip the throttle (foot on accelerator then immediately off), RPMs initially rise, then fall and then rise after a second or so to where they would usually rest with the amount of throttle given. this "lag" is more apparent the more throttle you give it so, again in park, if I hit the floor with the pedal and immediately release, the RPM's initially rise then fall then after 2-3 seconds it races the engine as if the pedal was put to the floor and then gradually decreases back to idle. I understand the LS being drive by wire but this throttle/transmission lag got to the point where I was waiting about 4-5 seconds with my foot at about 50% throttle before the car moved, this was from standstill.

I will try the manual downshift on my drive home from work, thanks for the idea! but I remember there is a lot of lurching when manually (or in drive) changing up through gears under acceleration.

[GrahamG]

Excuse me if stating the obvious but a relatively easy and cheep check would be of the various vacuum hoses. Nineteen years is just the time for them to start to crack and perish.

Sure would like to see you sort this problem,

Good luck.

[GrahamG]

Oops! cheep cheep!

[LEDMaestro101]

Obvious is just what I need it seems, didn't even think about the vacuum hoses! I'll check them when I get home this evening. Didn't even occur to me to check for leaks haha, thanks for the hint! Cheep haha, lets hope I don't have a Budgie stuck in my engine 😜

[LEDMaestro101]

Ok, update! my route home consists of various acceleration points so I had plenty of testing points. So, results: (driven in D unless otherwise stated)

Pulled out from work onto a 30mph road, gave around 60% throttle as a car was approaching (plenty of space) but car failed to move for about 3 seconds and I had to brake to avoid pulling out in front of the approaching car, at which point the car tried to pull forward from where the accelerator had been pushed down. Attempted to pull out again and car eventually moved but felt like a rodeo bull, lurching as it gathered speed up to 30mph, all up shifts very noticeable  

Merging from 30 slip road to 40mph main road, gave enough throttle to change down one gear (I think to 3rd) and car pulled as expected and climbed to 40mph quickly. 

Going from 40 to 50mph, used cruise to accelerate and it gathered speed in the usual cruise way, smoothly with no noticeable change in gear. Car has never had any issue when accelerating with the cruise control.

slowed down into a 30 (no down shifts noticeable) and then then put it into kick down to accelerate into a 50mph. Shifted down through each gear very noticeably and accelerated harshly and (again) like a rodeo bull with the same back and fourth lurching, as if the clutch had been let out too quickly on a manual transmission. Once it got passed 2nd gear it was smoother and more consistent but still lacked a bit of initial power as if it was hunting for each gear. Also, when it’s lurching, the revs bounce a bit as if the accelerator is being constantly pressed and released, even though it’s position didn’t actually move.

Went from a 30 to 60mph twice. First time was in kick down as above, with the exception that I released the pedal off the kick switch once it settled on a lower gear and the power delivery seemed to be somewhat smoother but still seemed like it was being held back. The second attempt I manually dropped it into 2nd and floored it to just before kick down and then changed up when needed, no hesitation or lurching noticed and gear changes up were smooth. 

One thing to note, when manually shifting down from D to 3, the car does it quickly and smoothly but when going from either D or 3 down to 2, it feels like the car is hunting for the gear. The car coasts (as if in neutral) for a good 1-2 seconds and then finds 2nd with quite a jolt. Perfectly fine going from 2nd to L though.

very long but needed to be thorough in hopes this may lead someone’s mind to think to a possible solution! Oh and PWR mode didn’t seem to relieve any of the symptoms.

 

[The-Acre]

Does the engine rev smoothly and consistently in P and N?  From what you describe I can't help wondering if the dreaded coolant contamination had already happened under the previous owner.  For most of those that this has happened too it seems there has sadly been little success in restoring full transmission function. Depending on the car's condition etc, maybe it's worth contacting lexussparesdirect (Paul Frost) as he breaks LS's and always has transmissions?  The LS transmission should be smooth and seamless and changes virtually unnoticeable.

[LEDMaestro101]

The revs are smooth but only when throttle input is also smooth. when "blipping" the throttle, it does the up, down and up to normal revs I described a couple of posts back. exactly the same situation in P and N. I was afraid someone might think that! As I said previously, when I changed the radiator a few months ago, the fluid coming from the transmission was brown/black so had probably never been changed nor added to. Only 109,000 on it when I bought it though so I would have hoped that the contamination wouldn't have occurred so soon into the cars life. I will contact Paul and see what he suggests, thank you! I've swapped out boxes between IS200's so I'm sure the LS wouldn't be to difficult to do in a weekend....worst case scenario!

[C Mclean]

Probably a fault with the engine rather than the gearbox. If it was a gearbox fault, then the revs would rise without the car moving. Maybe have a look at the signal from the accelerator pedal to the engine throttle body. Not sure if a generic OBD scanner will be able to show the voltage change as the pedal is pressed.

[LEDMaestro101]

the pedal position sensor was my initial thought too but as there is a primary and secondary sensor within the sensor body, I would have assumed an error code be thrown if either of the two readings were out of spec. I'll plug in my reader on my lunch break and check out the values from the sensor. Failing that, i'll go the ol' fashioned route and stick a multimeter on the sensor pins! thanks for the input!

[LEDMaestro101]

Ok, update time again. So it’s been stupidly hot driving weather over the past 3-4 weeks but today it has been chucking down with rain, max temps of around 20 outside. The car ran almost flawlessly! There was almost no hesitation and pretty much no transmission shudder/jerking. Could it be that my ATF is getting too hot in normal driving? OBD reports ATF temp being 84 degrees, I’m not sure if it’s any different to when it was acting up or not. Can others confirm (if possible) if that temp is about right? I’m going to be removing A and B shift solenoids and cleaning them up over the weekend as it was always 2nd gear I had hesitation with. Perhaps it is just gummed up from the old ATF and now the new stuff is working it’s way through. Will report back when I find something useful 

[Cotswold Pete]

13 hours ago, LEDMaestro101 said:

Ok, update time again. So it’s been stupidly hot driving weather over the past 3-4 weeks but today it has been chucking down with rain, max temps of around 20 outside. The car ran almost flawlessly! There was almost no hesitation and pretty much no transmission shudder/jerking. Could it be that my ATF is getting too hot in normal driving? OBD reports ATF temp being 84 degrees, I’m not sure if it’s any different to when it was acting up or not. Can others confirm (if possible) if that temp is about right? I’m going to be removing A and B shift solenoids and cleaning them up over the weekend as it was always 2nd gear I had hesitation with. Perhaps it is just gummed up from the old ATF and now the new stuff is working it’s way through. Will report back when I find something useful 

So my guess would be some electrical issue.  From my experience electronics hates being to dry or way too wet, so when the humidity and tempature are just right, then failing joints on a board will not show up so much, and given your other comments, I was wondering if you have some ECU issue.  It could be a loose plug somewhere that is causing ECU to get incorrect signal, or could be a problem on circuit board.

Not that I would try this on Lexis, but when I have had similar problems with other electronics, I tend to flood the circuit with Servisol Switch cleaner, and if problem stops, BUT then comes back again as the cleaner dissapates (usually over a period of time) then I know I have a dry joint or some other 'dodgy' connect.

On the other hand you are not getting any codes, so maybe my idea here is a false one.

I cannot imagine the solenoids would be impacted much by difference in weather, but be wishing you luck and hoping your work over weekend solves problem.

[LEDMaestro101]

Thanks for the insight Pete! I've been reading (On the US forum) about people having issues with the trans ECU and wondered whether, as you said, the possibility of a dry joint or faulty connector could be to blame. I'll have a look for said ECU and check the wiring while I have the pan dropped over the weekend. If it is as simple as a dodgy solder joint or wiring issue then it's easy for me to fix thankfully! 

Great idea with the switch cleaner! May have to try that as a point to narrow down if any PCB issues are present in the various ECUs. I think my idea of the difference in weather is my attempt to "clutch at straws" at this point! 😂 Still, I shall report back if anything changes after the weekend.

[Newbie1]

On 7/25/2019 at 8:45 AM, LEDMaestro101 said:

So, I ran through 15 litres of ATF to clear out the old (black) fluid 

It may not be your problem, but the transmission has suffered serious wear by the time the fluid is black.

[Britprius]

Problems with dried out capacitors are common on ECU's of your vintage. They can be replaced easily, and cheaply, and are readily available from sources such as RS components, and even in kit form on the Bay.

John.

[LEDMaestro101]

I was hoping the gearbox would be relatively fine.....I'm hoping there is little damage to it but I will find out after cleaning the solenoids.

Thanks for the input John, I'll pull the ECU and see what state the Caps are in, I've probably got some of the right value lying in my cupboard! 

[GrahamG]

I have no first hand experience but have read extensively on the subject and I would not be so concerned about the 'darkness' of the ATF. Plenty of sealed for life boxes have the ATF replenished  after many miles and it is described as 'black' but there is no problem with the transmission.

What is of concern is if the ATF smells burnt.

Good luck

[LEDMaestro101]

it was pretty dark, almost black but I don't recall it smelling burnt. Smelled more like warm metal than anything else but certainly not a distinctive burning smell. My thoughts (and hopes) are that my issue seems to be isolated to 2nd (possibly 1st too) gear and I'm hoping that cleaning the relevant solenoid will do the trick. If not then it's a relatively quick and easy way to narrow down the list of possible causes, the worst being a fried gearbox!