92lexus

hi everyone, Im a proud ownwer of a 92 Lexus Ls400 but I do have a question regarding a misfire at certain rpms, First, I have replaced the plugs, plug wires, distributors , and the misfire is still there. The misfire is very rough and seems to occur as I hit a little over 2000 rpms, when I decelerate it seems to go away but if I try and give it gas , the misfire continues. I've been all through the engine and performed a few tests , I am starting to get a little confused now.Could it be the fuel regulator going bad? Where is the fuel regulator located? If anyone can help I would be greatly appreciated. Thank you, Barry 92 lexus

meZoom!

just curious, what did your old spark plugs/pins look like when you replaced them (i mean, how did ALL of them look, comparatively)?? and the coils too? what kind of spark plugs do you use?
After all that you went through and you R&R'd, I don't think it's misfire/spark plug related (unless you used aftermarket), per se!! must be something else... can you describe also what happens during this "misfire?" my ES has started to do some funky accelerating also...
sorry to "answer" your question with more questions

GSquicksilver

did you ever change your fuel filter?

Lvangundy

I had the same problem, turned out to be the torque master plugs.

Replaced with toyota factory spark plugs and problem went away.

There's a rare chance the wires could have been bad. Check them with a ohm-meter.

JBrady

First thing I would do is replace the throttle position sensor. This unit wears at the most common throttle position and 2000rpm is a VERY common engine speed. This is a replacement item and even if it doesn't fix your problem should be done anyway.

If the above does not fix the problem I would suspect one or more fuel injectors. Injectors can get dirty and or worn and create poor response and poor spray patterns.

Other things include the emissions system, MAF sensor, coil packs, fuel pressure regulator, as well as more serious problems.

Lextreme

Sounds like a TPS problem

dunn378

how much does the TPS cost and does anybody know where the adjustments are suppose to be?

92lexus

First, I would like to extend thanks to those who have helped in my question, yet, I am still struggling with the timing problem. I am left with one more question, how much is a throttle position sensor and where can i get one, thanks again,barry

JBrady

Your local Lexus dealer will have the part. I am not certain but should be WELL under $100 probably $40 or so. Installation an proper setting should be done by someone who knows how. The dealer can do it or any private shop specializing in Toyota/Lexus.

FaceUT

I have a 92 LS400 as well and seem to have the same problem at 1800 RPMs - It almost seems like the car is guessing when I cruise at this rpm. Doesn't do it when I pass 1800 on my way up. Only when the engine is not under load.

I would be very interested in being notified of what you discover regarding the TPS.

Thanks!

Lvangundy

Updated TPS for LS400 p/n

894520 - 22090

Here's a thread with a little about the TPS -
https://www.clublexus.com/forums/sho...&highlight=TPS

92lexus

First, I would like to extend thanks to those who have given me many solutions to why I may be having a misfire at 65 mph. As the days went by and I studied the miss I started to understand more of what instances may be causing the miss. After I did a complete ignition tuneup as well as other upgrades nothing seemed to help with the miss. well, to make a long story short, I noticed that my overdrive would suddenly kick off while driving causing my car to have a misfire sensation. This led me to believe that there may be a problem with the O/D switch. I dug in to the shifter where the switch is located , and discovered bare wires were touching each other and sending false signals to the throttle components which control when the car is in overdrive or vice versa. So, my first task was to test my findings, I completely covered the wires and separated them from crossing. Well, there is no more miss now and when i figure out how to lengthen the wires in the shifter I will finish the job. The lesson here is, if you decide to go into the shifter be very careful when lifting it off because the O/D switch wires are very short and will posibly break causing the same problem I have endured. If anyone has any questions on this please ask me, thanks ,barry 92 lexus ls400

Lextreme

92Lexus,

Good job.

As for some of you want to change the TPS. There are two TPS in our lexus. I assume it will be primary and secondary. The TPS has two small screws and a plug for the signal. Installing it back is slightly tricky, but very easy. Just make sure the spring loaded contact in the TPS is re-oil back when you install it. It should not take you more then 3 minutes to change it. Just use a phillip screw driver.

As for me, i change two or three times already. The primary TPS(the first one near the intake) does not do much with adjustment. The adjustment is about few degrees. I would say just match up the old one. The secondary TPS affect idleing RPM. Turn it clockwise will increase RPM and counterclockwise will low rpm.

Good luck

92lexus

hey Lextreme, how are you,
thanks for looking out. I do have a quick question, where are the tps located and how much are we looking at paying for one, or two. Also, I just bought a new starter for my lex and was just wondering how much of a job it may be, hopefully not to hard. if you have noticed i do all my own work, by manual and of course the info i get from this forum, so it saves me a lot of money and ive learned so much about the lexus automobile. thanks for your help,
92lexus

Lextreme

The TPS (s) are located by the throttle body (TB) in the anterior part of the TB. Its black with two screws along with a medium size harness. There are two TPS. Make sure you find out which one is broken. An OBDI scan will tell you that. The first TPS is for the TB and the second TPS is for Traction Control. Its very simple to change it. You can do it less than 3 minutes. Cost? The list price is about $95 dollars. Email me info@lextreme.com I know a dealer where you can get it for $79.