Engine Or Transmission Causing "chugging?"

[JeffreyV]

I need some advice please. I bought a 1992 LS400 about a year ago. I had 58,000 miles on it (now 64,000). About a month ago it started "chugging." It's OK when cold... for the first 3 or 4 miles. After that it "chugs." It does this only when I'm trying to maintain a steady cruising speed (happens at all speeds... 30, 40, 50, 60 mph). It goes away if I accelerate or if I take my foot off the gas pedal. Sometimes goes away after the car gets good and warm. It shifts fine (goes into gear right away, no slipping, no hesitation, no tranny noise). My mechanic said it's the transmission acting up so he changed the transmission fluid (removed the pan and replaced the filter) then refilled with Toyota T-IV. Then he ran it, drained it with the plug on the pan and refilled again. I've driven it almost 60 miles since he did that and notice no difference.... at least not yet. I bought enough new T-IV to run it then drain 2 Qts by the plug three more times. Will it begin to clean itself with the new fluid? I don't want a trans flush. He said it was the original pan seal from the factory. He checked the engine and said it's OK. He had installed a new timing belt and new plugs 12 months ago. I use Seafoam periodically in the gas. So what's going on??? Jeff "byerjv@yahoo.com"

[90LS400Lexus]

Does it seem to be doing it when its in overdrive, like when the lock-up converter is engaged?

[amcdonal86]

Does the car ever stall out? This description may be somewhat helpful:

http://ezinearticles.com/?Torque-Converter...p&id=113485

[landar]

Chugging... Did you happen to get the LS400 "Choo-Choo" edition? B)

By chugging, do you mean "surging"? Transmission "hunting"? Is the engine RPM fluctuating?

I am having a hard time visualizing this "chugging".

[JeffreyV]

Does it seem to be doing it when its in overdrive, like when the lock-up converter is engaged?

Thank you for your interest. I spent about three hours searching this site and found a couple other posts with this same problem, but I can't see where anyone has solved it. One post said "it only happens within the first 1/4 inch or so of pedal travel." Same with mine.... It's most noticeable after I feel the transmission shift at about 45mph. But, if I use the button on the shifter to take it out of overdrive, It still does the same thing, only at higher rpm, of course. I came to a stop light yesterday, then when I took it back up to 50mph, the symptoms had disappeared... only to reappear about 10 miles later. My mechanic thinks it's the lock-up converter sticking, but I'm still not convinced. Could it be the injectors are clogged or the the throttle valve needs cleaning? I drained another 2 quarts and refilled with T-IV after my drive yesterday and took the tape off the wires in the trunk. They all look real good, but I left them hanging there anyway until I get this resolved. Does a lock-up converter engage when in 3rd gear? I also disconnected the battery yesterday for about 15 minutes and reconnected to see if that changes the symptom - if only temporarily - as I thought it might be a computer problem. I've yet to drive it since I did the three things just mentioned. byerjv@yahoo.com

[JeffreyV]

Chugging... Did you happen to get the LS400 "Choo-Choo" edition? B)

By chugging, do you mean "surging"? Transmission "hunting"? Is the engine RPM fluctuating?

I am having a hard time visualizing this "chugging".

My mechanic used that word to describe it. I guess you could say it "jerks" kinda like it's "hunting" for overdrive. The RPM stays rock steady. It keeps doing it if I take it out of overdrive using the button on the shifter.

[JeffreyV]

Does the car ever stall out? This description may be somewhat helpful:

http://ezinearticles.com/?Torque-Converter...p&id=113485

No, it never stalls.

[JeffreyV]

Does the car ever stall out? This description may be somewhat helpful:

http://ezinearticles.com/?Torque-Converter...p&id=113485

No, it never stalls.

That was some good info in that Torque-Converter-Lockup article. But, I don't seem to have any of the three symptoms described there (although possibly it's engaging in gears that it shouldn't be engaging in... I can't tell for sure.) It says the TCC is made to engage in high gear. I assume it could happen in 3rd or 4th gear since I have the button to take it out of overdrive. Third could be considered the high gear. Should I try to disconnect the TCC and see if the symptom disappears - as only a test... the article says "Most lockup converters are controlled by a wire or wires that plug into the transmission. It is possible on some models to simply disconnect this plug. This is not a problem and will only cause you to lose a little gas mileage. The RPM's will run slightly higher than before but will not harm anything or be an issue."

[amcdonal86]

That might be a good place to start.

[93ls400walt]

hove you checked for any trans. codes? My 93 ls does this now and then I have a trans code ( read off of the O/D light ) showing a code for one of the vehicle speed sensors.

[JeffreyV]

hove you checked for any trans. codes? My 93 ls does this now and then I have a trans code ( read off of the O/D light ) showing a code for one of the vehicle speed sensors.

I'm not sure if my mechanic checked for transmission codes. I'll ask... he said to bring it back if the drain and refill didn't help and he'll investigate further. Does the equipment to check transmission codes hook up at the same place as the engine diagnostic equipment? Do you check the transmission with the O/D on or off? Does yours jerk mainly at 45 to 55? Mine used to be OK after it warmed up... not so anymore... it seems like it does it every time I drive it. Not so noticeable on a rough road or when driving slow in town. But, I want it fixed. Jeff

[93ls400walt]

Mine seems to be in that MPH range. I do not have a constant chug just one or two every now and then.

To check:

Use either DLC

turn ignition switch on, do not start

push O/D button on

use wire to jump E1 and TE1 on the DLC

read the O/D light flashes

I have cel code 42 for No 1 vehicle speed sensor

[JeffreyV]

Mine seems to be in that MPH range. I do not have a constant chug just one or two every now and then.

To check:

Use either DLC

turn ignition switch on, do not start

push O/D button on

use wire to jump E1 and TE1 on the DLC

read the O/D light flashes

I have cel code 42 for No 1 vehicle speed sensor

Thanks so much! That's a big help. I'm sure my mechanic will be able to use it. I'm not much of a mechanic. What does DLC stand for? Thanks again! I'll be sure to let you know (post on this site) how things turn out, but it might take a couple weeks.

[93ls400walt]

The DLC is the diagnostic connector. one on top of the engine drivers side. And one under the drivers side dash.

[90LS400Lexus]

I asked because sometimes when mine is in overdrive around those speeds and I quickly release the accelerator and press it quick again, it will kinda jerk a couple of times, but I was assuming it was from my completely worn out engine mounts and transmission mount allowing slack to cause that.

Otherwise my transmission shifts flawlessly and smoothly through all gears.

[JeffreyV]

I asked because sometimes when mine is in overdrive around those speeds and I quickly release the accelerator and press it quick again, it will kinda jerk a couple of times, but I was assuming it was from my completely worn out engine mounts and transmission mount allowing slack to cause that.

Otherwise my transmission shifts flawlessly and smoothly through all gears.

Do you know where the speed sensor is located? Outside the transmission?

[90LS400Lexus]

Do you know where the speed sensor is located? Outside the transmission?

Not sure, but on my old 1991 Honda Accord it was on the outside of the transmission and was very easy to change.

[Marklouis]

I hope your mechanic is knowledgable in imports. a diagnostic check is always the first thing to be done (on most cars with OBD1 or OBD2) - and most likely it is a faulty sensor causing your woes(hopefully an easily replaceable one). These trannys are almost bulletproof and yours with such low mileage im pretty positive the Fluid and filter was fine. Glad you replaced it with the recommended type though. please post the results of your findings!

Good Luck!

[eatingupblacktop]

I need some advice please. I bought a 1992 LS400 about a year ago. I had 58,000 miles on it (now 64,000). About a month ago it started "chugging." It's OK when cold... for the first 3 or 4 miles. After that it "chugs." It does this only when I'm trying to maintain a steady cruising speed (happens at all speeds... 30, 40, 50, 60 mph). It goes away if I accelerate or if I take my foot off the gas pedal.

This is a long thread. Speed sensor maybe. To me sounds more like "Off-Throttle-Shock". NC described it as "It's reverse torque through the driveshaft". Lexus has a TSB for it. Looks not a cheap fix, but apparently works:

[JeffreyV]

I need some advice please. I bought a 1992 LS400 about a year ago. I had 58,000 miles on it (now 64,000). About a month ago it started "chugging." It's OK when cold... for the first 3 or 4 miles. After that it "chugs." It does this only when I'm trying to maintain a steady cruising speed (happens at all speeds... 30, 40, 50, 60 mph). It goes away if I accelerate or if I take my foot off the gas pedal.

This is a long thread. Speed sensor maybe. To me sounds more like "Off-Throttle-Shock". NC described it as "It's reverse torque through the driveshaft". Lexus has a TSB for it. Looks not a cheap fix, but apparently works:

I had seen that thread, but mine is a 1992. Also, someone said that if you take your foot off the gas with "Off-Throttle-Shock" then it would jerk... Here's part of the thread.... "Doug, crucial question: Is it doing it when you take your foot off the gas, like it's jerking a bit? Say you're just cruising at that 45-50mph window, nothing aggressive, then you take your foot of the gas to coast....is it jerking then?................ Response: It is just jerking when I let off of the throttle just a bit. If I am accelerating, even very slowly, there is nothing but smoothness……...it's you engine computer...you have what is known as "Off-Throttle-Shock", which is part of the largest technical Sevice bulletin ever issued on the car. I had this too on my 95."

So, I'm thinking it's the lock-up on the torque converter. I think it's probably meant to lock-up in both 3rd gear and in overdrive. That's when it jerks. I haven't been able to make it jerk if I drive with the shifter in 2nd gear and keep it around 1500 to 2000rmp, just like when driving about 50 mph in overdrive. I'm going to see if it can be disconnected. Does anyone know if the lock-up feature can be unplugged/disconnected on a 1992 LS400? Temporarily - as a test. Thank you!

[don corleone]

does the car jerk when you shift to drive or reverse. if so then you might need to adjust your throttle cable. common problem on LS'. also you can check the engine and trans codes if you go to lexls.com. very simple you can use a paper clip or small wire.

[JeffreyV]

does the car jerk when you shift to drive or reverse. if so then you might need to adjust your throttle cable. common problem on LS'. also you can check the engine and trans codes if you go to lexls.com. very simple you can use a paper clip or small wire.

It never jerks when I shift into drive or reverse. It only jerks when trying to maintain a steady speed on level ground in both 3rd gear and in overdrive (most noticeable at 45 to 55 when in overdrive).... never in 2nd. It's a continual jerking every 1/2 a second or so. It feels like the engine is stumbling, but I'm almost sure now that it's the transmission. I'll take a look at the codes.

[JeffreyV]

Mine seems to be in that MPH range. I do not have a constant chug just one or two every now and then.

To check:

Use either DLC

turn ignition switch on, do not start

push O/D button on

use wire to jump E1 and TE1 on the DLC

read the O/D light flashes

I have cel code 42 for No 1 vehicle speed sensor

I used a wire to check for engine and transmission codes after work today. All I saw was rapidly and consistently flashing Check Engine and O/D Lights. OK - no problems stored in the computer. So, I decided to clean the throttle body. I sprayed it until it was spotless then oiled the shafts of the throttle blade inside the throttle body. A 20 mile drive and no jerking whatsoever. I think it might be too good to be true. But I came across a 19 page explanation of the TOYOTA ELECTRONIC CONTROL TRANSMISSION today. Wow, it explains everything about shifting, lock-up, etc. It also said "says “The throttle position sensor (connected to the throttle body) gives the Electronic Control Unit an indication of engine load to control shifting and lock-up timing.” Hmmmmm??? It says that Toyota's lock-up works in all gears except first... If the shifter is in "D" position. It also talkes about the water temp sensor which prevents shifting into O/D or lock-up until the coolant reaches a predetermined temp. If anyone wants a copy, I'll scan it. email me at byerjv@yahoo.com.

[amcdonal86]

I used a wire to check for engine and transmission codes after work today. All I saw was rapidly and consistently flashing Check Engine and O/D Lights. OK - no problems stored in the computer. So, I decided to clean the throttle body. I sprayed it until it was spotless then oiled the shafts of the butterfly inside the throttle body. A 20 mile drive and no jerking whatsoever. I think it might be too good to be true. But I came across a 19 page explanation of the TOYOTA ELECTRONIC CONTROL TRANSMISSION today. Wow, it explains everything about shifting, lock-up, etc. It also said "says “The throttle position sensor (connected to the throttle body) gives the Electronic Control Unit an indication of engine load to control shifting and lock-up timing.” Hmmmmm??? It says that Toyota's lock-up works in all gears except first... If the shifter is in "D" position. It also talkes about the water temp sensor which prevents shifting into O/D or lock-up until the coolant reaches a predetermined temp. If anyone wants a copy, I'll scan it. email me at byerjv@yahoo.com.

This is fantastic news! I hope the problem doesn't come back.

Please keep us posted if it does!

[TexasLexus94]

My 94LS has the same "jerky" problem at around 45 mph. It's not getting better or worse, it just is always there. Seems like a tranny thing. But since the A/C went out at the end of the Summer (and I live in Vegas, whew), and that now there is a slight rat-a-tat sound when just starting to accelerate and then when stopping, I think the LS is ready for dismissal. I'm going to drive it to its end, and then buy a Kia, or a Honda, or a Fisker Karma (I wish). Sad, a beautiful car, bought it with 97,000 miles, only 119,000 miles now, but there comes a time when you must say goodbye to an old friend. Best highway cruiser ever....