1997 Ls 400 Won't Rev Beyond 4000

[MUDGUTS]

Hi,

Looking for some advice with a 1997 LS400.

Everything works as it should, no warning lights, no problems below 4000 RPM.

If you floor the throttle whilst either in N or D the car won't rev beyond 4000. The emissions have been checked and are perfect.

Also the recovery guy was certain it was the left CAT.

I'm looking for ideas.

Thanks in advance.

[hondansxr]

hi does it have a mass air flow meter or air meter...as this might no show on eml...try a diagnostic check..

[MUDGUTS]

hi does it have a mass air flow meter or air meter...as this might not show on eml...try a diagnostic check..

...Well this is the problem, the garage doesn't have a facility to run a diagnostic check on a Lexus. I have asked them to look into the CATs as the recovery guy was very sure this was the problem.

I don't really want to have to take it to a main dealer.

There is going to be a point where I have to bite the bullet and do that.

I am located in Northampton, is there a recomendation for a reasonably local solution with the diagnostics. I have been told that the Toyota dealer will not touch a Lexus. I have confidence in the local garage it is with now but the lack of a diagnostic check is slightly frustrating.

[Mybikesacx500]

I suppose blocked cats could be the problem, but what about a restriction on the intake side- I had a motorbike once that wouldn't rev, it started and ran fine, the problem turned out ti be the air intake filter, it looked clean, but I think it was blocked, I think by pollen.

You could take the air filter out for a test run

[ambermarine]

Hi,

Looking for some advice with a 1997 LS400.

Everything works as it should, no warning lights, no problems below 4000 RPM.

If you floor the throttle whilst either in N or D the car won't rev beyond 4000. The emissions have been checked and are perfect.

Also the recovery guy was certain it was the left CAT.

I'm looking for ideas.

Thanks in advance.

Hi

It as the symptoms of one of the oxygen sensors failing on the left or right bank these determine via information given by them to the Engine ECU how much fuel to give the engine for the right mixture under driving conditions demanded by the throttle.

If say the oxygen sensor is giving a signal of unburnt fuel when there is'nt any unburnt fuel then the fuel supply will be restricted when it gets to a certain preset rev range in the computer.The Oxygen sensor fails gradually allowing the engine to function but giving a timely warning to get the fault rectified .If you continue to run the car until it as completly failed the engine will not start or if it does it will run awfully and you will get a engine warning light.

There are sites in the USA that supply oxygen sensors relativly cheaply and they are not difficult to fit.The immediate task is to determine which of the oxygen sensors is failing.

There are two one to each side if you are unable to test them for electrical resistance as per the workshop manual instructions ,then a quick solution would be to replace them both, at a rough estimate of say $100 dollars its a lot cheaper than Lexus.

[beavisrules]

If it has the traction control option I'd look at the throttle body & motor (not sure if possible to actually look at them in action?) , also if it has a Throttle position sensor it's an easy item to check.

some more info that might help us guess :) -

fuel consumption - better/worse?.

when reaching 4000rpm does it stop dead @4000 , or hunt , range up/down , misfire ?

better or worse in hot/cold weather.

and we assume engine lights actually work ? (cant remember if they are bulbs or LED's)

[MUDGUTS]

Hi,

Looking for some advice with a 1997 LS400.

Everything works as it should, no warning lights, no problems below 4000 RPM.

If you floor the throttle whilst either in N or D the car won't rev beyond 4000. The emissions have been checked and are perfect.

Also the recovery guy was certain it was the left CAT.

I'm looking for ideas.

Thanks in advance.

Hi

It as the symptoms of one of the oxygen sensors failing on the left or right bank these determine via information given by them to the Engine ECU how much fuel to give the engine for the right mixture under driving conditions demanded by the throttle.

If say the oxygen sensor is giving a signal of unburnt fuel when there is'nt any unburnt fuel then the fuel supply will be restricted when it gets to a certain preset rev range in the computer.The Oxygen sensor fails gradually allowing the engine to function but giving a timely warning to get the fault rectified .If you continue to run the car until it as completly failed the engine will not start or if it does it will run awfully and you will get a engine warning light.

There are sites in the USA that supply oxygen sensors relativly cheaply and they are not difficult to fit.The immediate task is to determine which of the oxygen sensors is failing.

There are two one to each side if you are unable to test them for electrical resistance as per the workshop manual instructions ,then a quick solution would be to replace them both, at a rough estimate of say $100 dollars its a lot cheaper than Lexus.

Thanks for the suggestions guys, the lastest is that both CATs are in good shape and the garage found one fault code indicating a faulty oxy sensor, but no indication of which one...

Hopefully the guys will be able to narrow this down.

[steve2006]

I cannot understand why your local garage cannot diagnose the problem as most OBDII readers can read most codes on any make or model. Some just give you the code which you then look up but better ones actually come up with both the code and what it relates to.

Perhaps you could take the car to a good diagnostic centre to have the codes read and diagnose the problem more accurately, it is certainly cheaper than buying and replacing parts on a hunch especially when we are talking 4 O2 sensors on this engine and the universal ones are generally not up to the job.

[MUDGUTS]

I cannot understand why your local garage cannot diagnose the problem as most OBDII readers can read most codes on any make or model. Some just give you the code which you then look up but better ones actually come up with both the code and what it relates to.

Perhaps you could take the car to a good diagnostic centre to have the codes read and diagnose the problem more accurately, it is certainly cheaper than buying and replacing parts on a hunch especially when we are talking 4 O2 sensors on this engine and the universal ones are generally not up to the job.

I'm not sure how they did it but they got to the stage where they did find a fault code which indicated faulty Oxy sensor but not which one.

...Flash codes?

I think the number was 21

[ambermarine]

Hi,

Looking for some advice with a 1997 LS400.

Everything works as it should, no warning lights, no problems below 4000 RPM.

If you floor the throttle whilst either in N or D the car won't rev beyond 4000. The emissions have been checked and are perfect.

Also the recovery guy was certain it was the left CAT.

I'm looking for ideas.

Thanks in advance.

Hi

It as the symptoms of one of the oxygen sensors failing on the left or right bank these determine via information given by them to the Engine ECU how much fuel to give the engine for the right mixture under driving conditions demanded by the throttle.

If say the oxygen sensor is giving a signal of unburnt fuel when there is'nt any unburnt fuel then the fuel supply will be restricted when it gets to a certain preset rev range in the computer.The Oxygen sensor fails gradually allowing the engine to function but giving a timely warning to get the fault rectified .If you continue to run the car until it as completly failed the engine will not start or if it does it will run awfully and you will get a engine warning light.

There are sites in the USA that supply oxygen sensors relativly cheaply and they are not difficult to fit.The immediate task is to determine which of the oxygen sensors is failing.

There are two one to each side if you are unable to test them for electrical resistance as per the workshop manual instructions ,then a quick solution would be to replace them both, at a rough estimate of say $100 dollars its a lot cheaper than Lexus.

Thanks for the suggestions guys, the lastest is that both CATs are in good shape and the garage found one fault code indicating a faulty oxy sensor, but no indication of which one...

Hopefully the guys will be able to narrow this down.

Hi

According to the LS400 workshop Manual ;troubleshooting diagnostic codes .

code 21 Main oxygen sensor signal on left bank. code 27 sub-oxygen sensor left bank code 28 main oxygen sensor right bank code 29 sub oxygen sensor right bank.hope this helps.

[ambermarine]

I cannot understand why your local garage cannot diagnose the problem as most OBDII readers can read most codes on any make or model. Some just give you the code which you then look up but better ones actually come up with both the code and what it relates to.

Perhaps you could take the car to a good diagnostic centre to have the codes read and diagnose the problem more accurately, it is certainly cheaper than buying and replacing parts on a hunch especially when we are talking 4 O2 sensors on this engine and the universal ones are generally not up to the job.

Steve

It is possible to read the diagnostic codes on your car by using the box terminals on the engine and the one in the drivers footwell .The method used is simply connecting the terminals within the respective boxes and reading the output either on the engine warning light or in the case of the transmission on the overdrive on off light. The information is transmitted in a series of intermitent flashes or blinks of the respective light,the signal is then matched up to whatever code it designates.

But unless you have access to the workshop manual were all the methods of terminal connections and codes are stored it is unlikely it will be of use .

It is also possible to check a heap of other components in the engine including the operation of the oxygen sensors and how good or bad they are.The Manuals there are two, are about £300 from Lexus but they do come up on eBay apparently from the USA and to all intents and purposes will cover UK and Jap imported Lexus cars.

[MUDGUTS]

Hi,

Looking for some advice with a 1997 LS400.

Everything works as it should, no warning lights, no problems below 4000 RPM.

If you floor the throttle whilst either in N or D the car won't rev beyond 4000. The emissions have been checked and are perfect.

Also the recovery guy was certain it was the left CAT.

I'm looking for ideas.

Thanks in advance.

Hi

It as the symptoms of one of the oxygen sensors failing on the left or right bank these determine via information given by them to the Engine ECU how much fuel to give the engine for the right mixture under driving conditions demanded by the throttle.

If say the oxygen sensor is giving a signal of unburnt fuel when there is'nt any unburnt fuel then the fuel supply will be restricted when it gets to a certain preset rev range in the computer.The Oxygen sensor fails gradually allowing the engine to function but giving a timely warning to get the fault rectified .If you continue to run the car until it as completly failed the engine will not start or if it does it will run awfully and you will get a engine warning light.

There are sites in the USA that supply oxygen sensors relativly cheaply and they are not difficult to fit.The immediate task is to determine which of the oxygen sensors is failing.

There are two one to each side if you are unable to test them for electrical resistance as per the workshop manual instructions ,then a quick solution would be to replace them both, at a rough estimate of say $100 dollars its a lot cheaper than Lexus.

Thanks for the suggestions guys, the lastest is that both CATs are in good shape and the garage found one fault code indicating a faulty oxy sensor, but no indication of which one...

Hopefully the guys will be able to narrow this down.

Hi

According to the LS400 workshop Manual ;troubleshooting diagnostic codes .

code 21 Main oxygen sensor signal on left bank. code 27 sub-oxygen sensor left bank code 28 main oxygen sensor right bank code 29 sub oxygen sensor right bank.hope this helps.

Thanks very much for this ambermarine. I have passed this on. I think one of the lambda sensors was looking much worse (from the outside) than the others, also I think it was one on the left bank.

This is all coming together...

[floggit]

Im probably way off track here but is it possibly by flooring the throttle in neutral ??? This has caused something to burn out.

Ive had mine for 4 years now and have never had a situation where i needed to foolr the throttle like that .These are luxuary cars.

Steve.

[Parrot of Doom]

Nothing should burn out, the engine limiter will act well before that.

I would suggest that in N the car might not rev that high anyway - certainly Mercedes don't. In D is a different matter.

[steve2006]

I cannot understand why your local garage cannot diagnose the problem as most OBDII readers can read most codes on any make or model. Some just give you the code which you then look up but better ones actually come up with both the code and what it relates to.

Perhaps you could take the car to a good diagnostic centre to have the codes read and diagnose the problem more accurately, it is certainly cheaper than buying and replacing parts on a hunch especially when we are talking 4 O2 sensors on this engine and the universal ones are generally not up to the job.

Steve

It is possible to read the diagnostic codes on your car by using the box terminals on the engine and the one in the drivers footwell .The method used is simply connecting the terminals within the respective boxes and reading the output either on the engine warning light or in the case of the transmission on the overdrive on off light. The information is transmitted in a series of intermitent flashes or blinks of the respective light,the signal is then matched up to whatever code it designates.

But unless you have access to the workshop manual were all the methods of terminal connections and codes are stored it is unlikely it will be of use .

It is also possible to check a heap of other components in the engine including the operation of the oxygen sensors and how good or bad they are.The Manuals there are two, are about £300 from Lexus but they do come up on eBay apparently from the USA and to all intents and purposes will cover UK and Jap imported Lexus cars.

Very True, models up to October 1994 had OBDI diagnostics as you correctly point out and the codes are accessed by either the engine or passenger compartment diagnostic sockets, most of the codes are listed on lexls.com.

Models built after this date were OBDII compliant and therefore follow the normal code reading proceedures with the main codes being universal across all makes and models.

The EU had to of cause then step into the picture with the introduction of EOBDII.

It has now got to the point with CANBUS systems where even changing a light bulb can mean a trip to the dealer! OK maybe not for a light bulb but a radio swap is no longer a DIY job as the new one has to be coded to the car, when I started all I had to worry about was making sure it was either positive or negative earth!

[MUDGUTS]

Hi, the oxy sensor has been replaced and now the car has no fault codes stored, however it is still holding back.

The garage have replaced the fuel filter which was pretty dirty: A lot of brown fuel came out. They will drive it later so see if this has changed anything.

[Parrot of Doom]

This is a random thought, but is the accelerator cable correctly set up? Will it rev past 4000rpm if you turn the pot manually, under the bonnet?

[MUDGUTS]

Thanks, I'll ask them to check this.

[MUDGUTS]

The latest is the throttle position sensor has been checked and is OK. The Fuel Filter change has made no difference and it is still holding back at around 4000 RPM.

The good news is that it needs a pair of wiper blades and a brake pipe to pass the MOT.

The garage are 75% sure it is the mass air flow meter.

Any advice with replacing this? Should I take the car to Lexus dealer to have them be 100% sure?

I'm going to collect it tomorrow and run it for a week or so (I need it to get to work and back) and then unless things are better, get it into Lexus MK.

Other info is that it did just under 2500 miles since its last MOT a year ago, I'm pretty sure it has been sat around for a while in the sales lot. So maybe a good run and a bit of heat could help, is it possible damp is a factor?

[Parrot of Doom]

Who makes the MAF? If it's a Bosch part you can just buy from them, you'll save a hell of a lot of money doing that than buying from a dealer.

[MUDGUTS]

Who makes the MAF? If it's a Bosch part you can just buy from them, you'll save a hell of a lot of money doing that than buying from a dealer.

I don't know. I'm going to collect it tomorrow and double check the electrical connections to this. I do have one question though: Is the MAF Sensor the whole assembly (the bit the air goes through and the electronics)? or is it in two parts? I see a few on eBay and also there is the posibility of getting one from a vehicle breaker.

What I will do though is get it to the Lexus dealer and have the fault 100% confirmed before spending any money on replacement parts. Obviously there is Toyota and Lexus parts on the web to try.

Thanks to everyone for their help so far.

[Parrot of Doom]

I haven't checked (I'm fairly new to Lexus ownership) but it should only be a little thing. If it's screwed into a larger plastic housing then you should be able to separate it and order only that part - the plastic housing bumps up the price.

It's like ordering a new air filter box every time you replace the air filter.

Have a close look around the thing, see if it has any part numbers stamped on.

[beavisrules]

Have you only just bought this car?

[MUDGUTS]

Have you only just bought this car?

Yep, I got it very cheap and it was a gamble. It only had about about a month or so MOT left. I got it for £884.

So it's cost me an Oxy Sensor, which was generating a fault code (now no codes are generated), a fuel filter (which was filthy) and some labour time for inspecting the CATS. At this stage I'm going to take it away today with a years MOT on and run it for a few days. During that time I will double check all the connections to the MAF sensor and get some pics of it including the part No.

If this can be resolved I have got a good car for a reasonable price. My hand was slightly forced as the previous car failed the day I started to look around for a Lexus, I would have liked to look at a few more, but this was one of the better ones as far as condition was concerned. For something similar I was looking at nearer to £2000. One thing I noticed was that the ones I did see didn't have much MOT on them.

[MUDGUTS]

I haven't checked (I'm fairly new to Lexus ownership) but it should only be a little thing. If it's screwed into a larger plastic housing then you should be able to separate it and order only that part - the plastic housing bumps up the price.

It's like ordering a new air filter box every time you replace the air filter.

Have a close look around the thing, see if it has any part numbers stamped on.

Thanks P.O.D, I will do that. I'm tempted to try to clean it but might just leave that to the connections.