1997 Ls 400 Won't Rev Beyond 4000

[Rupert Dubreaux]

Hi,Phil

Those pics look exactly like the OBD1 diagnostic port on my Mk2 .

[Dale_V]

Nope thats not OBD2 , thats just a Toyota diag port

OBD2 looks like this:

[MUDGUTS]

Thanks for the contributions, Gents.

This (OBD) is one of the reasons I want a 430 next time around (OBD2): When I took this to the Lexus dealer in Milton Keynes, they were pretty clueless and I don't want that to happen again.

I found some info on Club Lexus http://www.clublexus...ion-issues.html

Most, if not all of the things tried there have been looked at on mine, including bypassing the fuel pump ecu (or similar).

Driving home on the motorway recently, I thought the issue had gone away, when I floored the throttle, the car responded instantly, whereas normally it seems to trim back the fuel, as if taking your foot OFF.

2 days later I tried flooring it again and the car dropped a gear and the RPM went to about 5000 and swung about wildly while the car stayed at its current speed. Once I took my foot off the throttle, it changed up and carried on as if nothing had happened.

I'm coming up to 15,000 miles in this now and it's actually very drivable, provided you don't expect it to take off when you floor it. The MOT is next Monday. If it's OK, I'll be keeping it for another year maximum.

[Dale_V]

Shame youre a distance away, I've a spare 1997 LS400 you could have swapped parts from to test on yours.

Did I read something a while ago about the 2 throttle/shift cables sometimes being out of sync and causing issues?

[MUDGUTS]

...I'm coming up to 15,000 miles in this now and it's actually very drivable, provided you don't expect it to take off when you floor it. The MOT is next Monday. If it's OK, I'll be keeping it for another year maximum.

Straight through the MOT this morning, NO advisorys

[Malc]

Just a quickie guys .......... in the real world ....... does anyone ever run their LS400 at 4000 / 5000 revs ???

Normal running, mine ( I think ) doesn't ever get past the early 3000's !

Malc

[Dave76]

does anyone ever run their LS400 at 4000 / 5000 revs ???

I stick to 56MPH on M/Ways (63 mile round trip on average & thats that, a long drive I would do more, I guess around the 2000rpm average, could be just over.

I have not yet tried 4 or 5000rpm drving through London (I live there) but I am getting there, sort of slowly.

[Dale_V]

Just a quickie guys .......... in the real world ....... does anyone ever run their LS400 at 4000 / 5000 revs ???

Normal running, mine ( I think ) doesn't ever get past the early 3000's !

Malc

yes mine goes to the 6000rpm redline pretty much everyday.

[MUDGUTS]

Update:

...nothing to report. It still runs perfectly in every other area but this one issue. I would spend some more money on trying to get to the bottom of this but have resigned myself to running it to the next MOT and then trading for a 430. I'm approaching 18,000 miles or so in it now (total is around 165,000).

[MUDGUTS]

...Well gents, I have done over 22,000 miles since purchase now and finally there is something that approaches a symptom manifesting itself:

I now get a high pitched whine from the rear: Sometimes as I first pull away and now I can re-produce it when I accelarate hard but as soon as I come off the throttle, the noise stops. It's like the noise is from a fuel pump or some similar component straining...yet the car starts and runs fine. Nothing else has changed apart from this, the car stil drives OK).

[ambermarine]

...Well gents, I have done over 22,000 miles since purchase now and finally there is something that approaches a symptom manifesting itself:

I now get a high pitched whine from the rear: Sometimes as I first pull away and now I can re-produce it when I accelarate hard but as soon as I come off the throttle, the noise stops. It's like the noise is from a fuel pump or some similar component straining...yet the car starts and runs fine. Nothing else has changed apart from this, the car stil drives OK).

Excuse my brevity but what does your doctor say about this condition? perhaps you have had too many mince pies over Xmas

[MUDGUTS]

...Well I have a few to go and also some more party food but I don't think that's the problem. :)

For info I have tried jumping FP and +B in the diagnostic port and the pump does seem to get a higher voltage, you can definately hear it then but otherwise it is silent. It certainly sounds like the noise I'm hearing. I think the pump is becoming noisy when it has to run faster.

Obviously this could be a red herring but I won't know until it's changed. The dilema is that this car is getting quite old now and I'm very reluctant to spend any money on it. My strategy now may be to run it until that pump fails and then have it replaced. If that fixes the fault, that would be great but I won't put any more money into it unless it needs it to keep it on the road. If the pump replacement is expensive, that would be the end for the car.

Does anyone have experience of these pumps failing?

[cruisermark]

i have never heard of pumps failing

Is the pump easy to replace - can you do it yourself?

If the answer is yes then perhaps you could buy a working pump and then ti over to see if it makes a difference

I think this will give you a cost effective and quick diagnostic to your problem and perhaos cure the problem

[steve2006]

They have been known to fail, I had a nearly new one up to a couple of weeks ago from a 97 I'm breaking, found a receipt for it in the pile of paperwork.

It could be worth checking the pick up on it.

Possibility?

http://www.ebay.co.u...=item231885b925

[MUDGUTS]

Some more developements:

This evening the whine is not only still there but seems slightly louder, so I conducted a bit of research: The noise ocurs just after start and definately when I floor the throttle, it will stay on, whining away, until I take my foot off the pedal. At the same time the engine will hold back as always, so the noise and the engine holding back are happening at the same time.

Also I tested the system that ups the pump voltage again by jumping FP and +B in the diagnostic port and the pump does seem to get louder, it's not so pronounced if the engine is off but with the engine running, the noise I hear is the same as described above, so now I can be fairly sure that the whining is from the pump working harder. My theory now is that the pump was never powerful enough to supply the extra fule demanded and that leads to the engine holding back somehow.

I'm going to get a new pump tomorrow and have it fitted as soon as possible. I'll try to keep the old one to carry out an autopsy on it and will post up the results

LOC (USA and Canada) below

http://us.lexusownersclub.com/forums/topic/70887-1997-ls-400-wont-rev-beyond-4000/page__st__15

[39buss]

Some one once said to me that a Lexus is restricted to 4000rpm when cold. If there's any truth to that maybe the said electronic gubbin is inoperative,broke,stuck or acting as if the 'choke' was still out when the engine has warmed up. You deserve to crack this as you've practically written a book and stuck with it all this time.

[ambermarine]

Is the fuel filter in a gunged up state ,that would reduce fuel pressure at the engine and make the pump work hard.

[MUDGUTS]

****UPDATE****

The problem is now resolved and I can confirm the car performs as it should do, right through the range, transmission operating correctly, etc.

Today the technicians at Thor Racing, Coventry, had a look at the fuel pressure and confirmed it was low, so had a look in the tank at the pump with the intention of replacing this, they also had a look at the fuel filter (which was clear) and after a good look around, discovered a fuel clamp, hidden away on the fuel pipe by the differential. Once removed, the fuel pressure was confirmed at correct, the car road tested and as I say above, it is 100% now.

Thanks to everyone who contributed to this thread, as SRK said on the USA and Canada forum the fuel pressure should be looked at. I think the voltage rise to the pump had been checked when the car last went in but we ran out of time to persue this any further and I have been living with it since I bought the car. The increased noise from the pump recently is still a mystery but the pump is now silent.

Somewhere a mechanic is missing a fuel clamp...

[wow300]

Lol... After all that.... Garages looked hard then !

[abs66]

Brilliant news.......now you will have some fun :-)

[39buss]

I think I'd have that pipe replaced in case the clamp has damaged the internals and it starts to break up inside or possibly leak. You dont want more bother after all the time and patience spent finding the fault.

[Bluesman]

You couldn't make it up. Well done and welcome back to the driving experience minus all the problem.

Any idea which garage may have left it on there?? Mike

[abs66]

Was it some daft attempt at fuel economy do you think? I've been trying to work out why it would be on the pipe but not fully closed.....strange...

[MUDGUTS]

The clamp was 'upstream' of the tank, so I guess it was put there before before a fuel filter change. I don't know when it was fitted but almost certainly before I got the car.

I have written to Lexus to complain about their diagnosis and to ask why they never checked the fuel pressure themselves and about the advice that they ‘remove the cylinder heads to check for excess carboning / decoke’. I can't see why they said this other than to price themselves out of a job because they were stumped.

[steve2006]

Looking at the rust on that clamp it's been there for some time and you would have thought that a professional garage would have spotted something as obvious.

As for Lexus,I don't blame you,there is no need nowadays to remove a cylinder head to check inside the engine just remove the spark plugs and put a Boroscope in there, shows everything on a monitor screen.

Have you let the guys on LOC.com know the outcome?