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I have an issue going on with what I think is the transmission but trying to research about it I haven’t come across this scenario.
If I drive my LS like a normal grandpa, maybe using 25% or so of throttle, it will shift and pretty much drive like normal. However, if I am cruising and then get on the throttle at maybe 75% to pass a car or maybe get up on the highway, I feel it kick down into a passing gear but then it just revs up to about 3K RPM and doesn’t really go anywhere. I will maybe climb to 3.2k RPM but at that point I’m still only doing about 40 mph or so and it never shifts up into a higher gear. If I then let off of the throttle and let the RPM come down it will shift into the higher gear as it should. Then if I go back to just normal 25% throttle it acts normal.
This just started happening last night. Tested it again after work keeping my fingers crossed that it was a fluke but knowing in the back of my mind it won’t fix itself, it’s doing it consistently. There are no error codes on the dash but I did use a scan tool that I have and it said it had a P301 error. I looked that up and it’s a misfire on cylinder #1 but I don’t think that’s it because it’s running normal along with the fact that the scan tool kept failing trying to erase the code. I figure that code is stuck in there from a previous issue possibly.
I did some Google searching and didn’t come up with anything with the transmission shifting like this. What I have seen are the posts about the hard shifting that ended up being the ECU that people sent off to SIA Electronics to fix.
Anyone have an idea on what it could be or do you think it’s possible the ECU like the issues for the hard shifting?
156k miles and the fluid probably hasn't been drained/filled. I've had the car since 110k miles and I haven't done it on this one. I really have a feeling it's not the fluid the way this one is acting. For $115 to rebuild the ECU I think I'm going to go that route first but I also need to schedule a drain/fill as well. Due to the detailed steps of doing a drain/fill I'll probably have a Lexus specific shop do that. I had a drain/fill done on my last LS and it was about $200 then which means it's probably $225 - $250 now. I'm going to call SIA electronics on Monday and see if they have heard of my issue before and if they think it's the ECU. Of course I expect them to say, Yes, it's the ECU but we will see.
Are you saying the rpms won't go higher if you keep the throttle down? If that's the case I would look at the engine as opposed to the transmission. The ecm repair is to fix hard downshifts and won't likely fix your issue.
Are you saying the rpms won't go higher if you keep the throttle down? If that's the case I would look at the engine as opposed to the transmission. The ecm repair is to fix hard downshifts and won't likely fix your issue.
They go higher but it's almost like it tops out at 3,200 RPM. I'll be honest, I did want to keep pushing it when I know something isn't right. According to what I read, the hard downshifts is the most common but not the only issue that could be caused by the ECM. I even saw a post where a Lexus mechanic that had a 430 replaced his trans and it ended up still having the same issue until he had the ECM repaired That's why I'm going to call SIA on Monday and see if I can talk with someone. I just don't have a lot to go on when I don't have any error codes to research.
If it was my car I would clean the MAF and then reset the codes found. It really sounds like an engine issue to me. How old are your spark plugs? Air filter in good shape? Any vacuum leaks? These can all lead to reduced engine performance and won't necessarily set a code unless they get really bad. Does your code scanner read live data?
The car runs and shifts fine unless I give it a bit of throttle at once, that's when it just doesn't shift right. I don't remember the exact mileage, I can look it up later, but I've changed the spark plugs since I've owned it. I haven't checked the air filter but that's a good idea to check. I don't know of any air leaks but I will say that I did pay to have my starter replaced less than a month ago and that's a fairly major under taking. It ran fine for a good 2 or 3 weeks after they replaced it before this issue showed up so not sure it would have been something they did. I can't think of what I would check that they might have unplugged or maybe messed up from the install but I'll pull the engine cover tomorrow and take a look around to see if I notice something loose or off. The code scanner I have is just a simple $35 dollar generic scanner. I tried to clear the only code it found but it kept erroring out on trying to erase it.
It's possible that the variable intake runner system isn't working correctly. It's attached to the underside of the intake manifold and runs off of engine vacuum. At higher rpms the butterflies in the runners open and shorten the length the air has to travel. If they don't open the engine will act sluggish and not want to rev at higher rpms.
I really still think you have an engine issue. The transmission will shift/act funny because it can only do what it's programmed to do. It's being fed faulty info when the engine isn't running correctly.
So the only way to check for the variable intake runner is to pull the intake? I just paid to have that done and I bet if I took it back to the place that did it they would charge me all over again. That labor was probably $800 of the bill.
I would start with a better scanner to see some real-time data to see how the engine is running. Your misfire code may be current and would explain your issues. You could also call the shop and explain the concern and see what their thoughts are. They did remove the intake and all the wiring which can cause other issues. If you search the misfire codes on this site you will see it is a common issue to have after touching the coil wiring on these engines.
But the motor sure runs smooth. When I replaced my spark plugs I did accidentally pull a wire out of the connector and I could feel it running rough. Even though the motor was running pretty good I knew it wasn't right immediately because I'm used to feeling it being completely smooth. I had to fix he wire to the connector and it was all good at that point. It doesn't feel like it has a misfire to me, however, you're correct that I need to probably get it on a better scanner. I'll probably get charged $150 or more just for a diagnosis just to do that. I'm going to call SIA electronics in the morning to talk with them just to see what they say. I've already pulled the ECM just a little bit ago and depending on what they say I might send it off to them just to rule that out. It's $115 if they fix it or $90 if they test it out and nothing is wrong. The biggest downside is having my car down for several days until the ECM gets back. If that doesn't work or if they tell me the symptoms don't sound like it's the ECM I will come back to the shop that replaced my starter.
Called SIA this morning and was able to talk to a tech pretty quick. He suggested I go and have the car's system updated first. I don't really want to take it to a dealership but I'm not sure the place I took it to for the starter replacement will be able to do that. I'll have to make some phone calls this afternoon to see what I can find out.
May I please suggest that you not waste your money here and there. Just take it to a lexus dealership and pay them the $150-200 Diagnostics. They should accurately Diagnose your problem or atleast narrow it down for you. You can then shop around for the fix urself Independently. Its the best way to fix The unicorn issues with our cars that are not common enough for others on this forum to accurately Spot diagnose. Good luck
Took my car back to the shop that did my starter and told them all about the transmission issues and the recommended ECU repair. After a couple days there and them reaching out to their contacts they suggested I go ahead and have the ECU repaired. After a couple weeks I finally got my ECU back from repair and it all looks to be working normally now.
I wanted to come back and give an update on this since I've been dealing with this issue for over 2 months now. After my last post, when I thought it was fixed, it turned around and actually started acting much worse. It got to a point that it ran terrible most of the time and I had to park it. After asking around I found a Toyota/Lexus master mechanic with over 20 yrs at the dealership and left and started his own place fairly recent. I had to wait a week before he could take it in but once it got there it took a little over a week troubleshooting all sorts of things and finally found the issue. I end up being a twisted/restricted fuel line. When the shop before this one replaced the starter they didn't get the metal fuel line back into the regulator straight and the rubber side of the hose which is a little above this connection it ended up getting twisted and restricting the fuel. He unhooked it, straightened the rubber part of the hose back out, and put it all back like it was supposed to be.
I got it back this afternoon and took out to test everything myself and I have to say it's running the best it has ever run before. I replicated the passing car scenario I originally posted and instead of falling on it's face it is now by far way quicker than it has ever been before. The acceleration from the down shift is fantastic now, way better than it has ever been. It pulls hard all the way to red line where it now has great shifting points. As part of all the troubleshooting over the last two months it's had the MAF replaced, Throttle body cleaned including the IAC ports, repaired ECM for transmission, transmission fluid drain/fill, and fuel injector cleaner.
I was honestly starting to look for a new car because I didn't think this one was going to get resolved. Now that it's running so good I'm not so sure what I'm going to do. Right now I'm just going to hang on to it but keep an eye out for a good deal on a 2013+ LS460 in the right color combo I want. I really do love the LS430 but at some point I'll probably have to upgrade.
07-30-21, 07:59 PM
2005 Shifting weird
