Help Needed - Live Data Reader For 1995 Ls400?

CptYossarian · August 10, 2015

'Evening,

My LS400 runs at 1,800rpm for about 3 minutes and gradually drops to the perfect 500rpm, after which it runs like a dream.

I've been advised by a very friendly local Toyota indepedent (Blue Streak Automotives - Tweed Road Northampton) that it is likely the temperature sensor that's gone wrong - essentially reading the engine temp as -15 or -30 degrees when it's cold so running the car very rich. He said that if he could diagnose this as the issue I'd be getting everything sorted for around £100.

Unfortunately my car is just too old for him to read the live data when starting the car up from cold.

Without having to go to a Lexus stealership and pay £99+VAT for an hour's labour just to have the car plugged into the system they have, I was wondering if it was...

A - possible to buy a contraption that reads data from a 1995 (M - registered January '95) as the car is started up from cold

B - possible that anyone on here knows of a garage well within the Northants area that has access to such technology that won't charge silly money for diagnosing this

This problem isn't absolutely critical - it just makes driving the car when cold very difficult, as it wants to creep at 30mph, so slow manoevering is more or less impossible, and I don't want to knacker the gearbox putting it into gear when it's running that high, nor do I want to wear out the disc brakes trying to reign the car in!

At present I can warm the car up in the mornings as I have the spare time, but I'd rather not do this, and fixing this issue will make the car mechanically spot on, apart from the 15 year old cambelt of course.

Any assistance would be greatly appreciated! :)

Thanks,

Tom

alien1974 · August 10, 2015

whats your fuel consumption like?

ambermarine · August 10, 2015

It is probably as easy just to put in a new sensor ,they are cheap and not difficult to fit.I fitted one in my Mark1 and it did resolve the problem which was much the same as yours

CptYossarian · August 10, 2015

whats your fuel consumption like?

Goodish. I do 18 miles a day to work and back mostly on a dual carriageway and pepper this with some trips into town. Last tank was 20mpg, tank before, which included a nice long run out to Grantham, across to Newark, and back down the M1 around 26mpg.

Obviously it's running very rich for the first few minutes when cold. You can see it coming out the exhaust even when it's well over 20 degrees C outside.

ambermarine - I can barely identify one end of a spanner from the other, and would rather not tempt fate messing around with sensors, unless' literally as simple as "unclip dud sensor from x compartment, fit new sensor into its place, try car". This chap at the friendly garage doesn't want to do this without any data showing that this is the problem though, which I can understand.

steve2006 · August 10, 2015

You don't necessarily need a live data recorder to confirm a correctly working CTS just a digital multimeter to measure the output voltage of the device or the resistance at certain temperatures.

The chart beow shows the expected range of resistance of the CTS at various temperatures but the main checked without a thermometer are at 20 degrees ( engine cold at this time of the years so expect 2000-3000 ohms and fully warmed up at 80 degrees so expect 200-400 ohms.

As Ambermarine mentions a new OEM replacement is quite cheap and there is a good DIY fitting tutorial on the forums.

If your independent is Toyota trained they should have the correct Toyota Tech diagnostic kit for OBDII diagnostics to enable live data reading.The engine temperature will not effect live data so I fail to understand why the data cannot be read with a cold engine as it comes from the engine ECU.

TBH £100.00 for the complete job including an OEM sensor sounds like a good deal.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE Temp. °F (°C) Ohms -4° (-20) 10,000-20,000 32 (0) 4000-7000 68 (20) 2000-3000 104 (40) 900-1300 140 (60) 400-700 176 (80) 200-400

CptYossarian · August 10, 2015

Very helpful post, steve2006, thank you for that information.

alien1974 · August 10, 2015

bearing in mind that these do rev quite highly when cold but soon calm down, mine does

Tinonline · August 11, 2015

Sounds OK to me.

But you might want to swop the sensor as a peace of mind action: it's done a few miles and years.

As long as you can get to it without having to faff about - should be a quick whip it out and pop the new in as quick as to avoid draining the coolant or having to overly worry about getting air out of the system.

Also...might be 20 degrees plus outside but your engine is cold compared to its normal operating temperature.

alien1974 · August 11, 2015

also you would have poor fuel consumption all of the time if your sensor was faulty

CptYossarian · August 11, 2015

Thank you for your responses.

I understand that the engine is very cold even at +20 degrees compared to its normal operating temperature...but I also believe that if the sensor misreads the temperature it will potentially run rich at the start.

Also, I know there are a few people about who've reported this type of issue...I could understand it running a little high when cold, being a big old engine, possibly 1,200 or 1,300rpm, but 1,800 seems excessive.

I haven't mentioned this yet, but it's very relevant - it's done under 4k miles per year for the last 10 years of its life - some MOTs were only 1,200 miles apart - so at first I thought I could reset the ECU and "learn" it a new start-up procedure. I did this using the fuse under the bonnet, and then took it for a good long hard run, and after this the car started up and ticked over at 1,100rpm or so for a few days, before reverting back to its old ways.

It also had a daft eBay resistor SUPERCHIP!!!1 on it when I got it which was doing between naff and all - I've ruled that out as having any kind of influence over it.

CptYossarian · August 11, 2015

You don't necessarily need a live data recorder to confirm a correctly working CTS just a digital multimeter to measure the output voltage of the device or the resistance at certain temperatures.

The chart beow shows the expected range of resistance of the CTS at various temperatures but the main checked without a thermometer are at 20 degrees ( engine cold at this time of the years so expect 2000-3000 ohms and fully warmed up at 80 degrees so expect 200-400 ohms.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE Temp. °F (°C) Ohms -4° (-20) 10,000-20,000 32 (0) 4000-7000 68 (20) 2000-3000 104 (40) 900-1300 140 (60) 400-700 176 (80) 200-400

My dad has the equipment needed to test this out....we just need to find the CTS (which stands for "Something" Thermal Sensor? You can openly laugh at me if you want). :)

Can someone chuck me in the direction of the tutorial/a diagram and I shall try not to bother you again!

alien1974 · August 11, 2015

CTS = coolant temp sensor have a look at this thread http://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/377171-diy-coolant-temperature-sensor-change-pics.html

CptYossarian · August 11, 2015

Oooh. Excellent. Thanks.

Titch LS · August 12, 2015

Tom, the superchip you're on about definitely will have an influence on the motor. It fools the ECU into thinking the engine is constantly running cold and so adds more fuel to make it run richer, thereby giving a "performance" boost. If you remove it, the car should "learn" to run better after a few days. It could bring the revs down a tad at start up. Worth a try.

CptYossarian · August 12, 2015

Sorry - I wasn't entirely clear on that point.

The very first thing I did when it was sat SORNed on my parents' drive was to remove the chip. We inspected the wires and connector after removing it and couldn't fathom what it could have been doing, as it didn't appear to be physically connected to anything in any way.

Either way, it was removed before I began using it as my daily, and following advice I saw elsewhere on this forum, I reset the ECU by removing the fuse for a few hours.

Unfortunately it still hasn't "learnt" to run better, and this morning revved at between 1900 and 2000rpm for the first minute or so before gradually dropping to the standard purr that is 500rpm.

There's definitely something up with it.

I would have suspected a clogged throttle body if resetting the ECU didn't fix it temporarily (i.e. for a few days).

Slobbo · August 12, 2015

I have the same year model and invested in an Autel unit that I was told would do the job but .........Doesn't. The unit I have is a very good workshop model but as the Autel guy said (after I'd bought it) that the car is just slightly too old.

CptYossarian · August 14, 2015

Haven't yet got around to doing the multimeter test, but something interesting happened today.

I drive around 9 miles each way to work and back, give or take, and let the car warm up before leaving in the morning. As mentioned, it revs high for a couple of minutes, then spends a couple of minutes at 1,100/1,200rpm and then drops to 500rpm.

Even if it didn't rev high I'd be inclined to leave it a minute or two before setting off to be kind to it - big engines + short journeys = coked up.

Anyway, I had to leave work and get home quickly today, so I got in the car, and set off before it'd done any warming up.

I then had to take a diversion, and this involved two very sharp bursts of acceleration onto a dual carriageway, firstly in one direction up to 60mph and then the other up to 70mph.

I felt rather guilty for treating a cold engine like this, and then on the way home something strange happened, which has happened before.

Without cruise control being turned on at all - active, rather - every time I lifted the throttle the car would maintain speed anyway, as long as it was flat. It's like the throttle was stuck, or rather the engine revs were not going down - no engine breaking perhaps.

I then encountered traffic, and the car refused to drop below 1,100rpm, and thus wanted to creep a little too fast. I tried putting it into neutral when traffic slowed up, and the revs bounced upwards and settled back to 1,100rpm.

The car was definitely completed warm by now as I'd driven 6 miles.

I then blattered the car onto a final dual carriageway stretch and kept it 3rd until 70mph - at the next set of lights it settled down to 500rpm tickover as per normal.

Soooo...could this weird behaviour, where the car seems to coast at a set speed, whatever speed I brake down to and lift off the throttle again, without cruise being activated, be explained by driving off when the engine was stone-cold (and, if the temp sensor was broken, when the car "thought" the engine temp was well below freezing)?

Sorry for the long post...I hope someone can offer advice! :)

steve2006 · August 15, 2015

Firstly with a fully warmed up engine the tick over speed should be 850 RPM +/- 50 so 500 is too low, the idle speed is controlled by the IACV ( Idle Air Control Valve) which have been known to stick and cause the problems you have however I would as a 1st action clean the TB ( Throttle Body) as this can also effect idle speed as they get gummed up and if it can't fully close will keep the revs up.

Never has a case but also check the throttle cable just incase it is sticking.

TB clean proceedure below

http://www.lexls.com/tutorials/EFI/throttlebody.html

CptYossarian · August 16, 2015

Hmmm, the thread you've linked to indicates that normal idle when warm is actually 650 +/- 50rpm, so 600rpm would be fine. I'll have to double-check the next time it's warmed up fully and idling.

It doesn't judder or stall when slowing down or at traffic lights.

I've got a guy who's happy to clean the throttle body as long as he knows it's likely to fix the problem I've been having - it's a little beyond what me and my dad are able to do (although I'll show him the excellent procedure above to see if he's happy to give it a guy).

I'm not going to deny that the throttle body might be clogged - it did well under 4k per year for 10 years - but because this issue can be temporarily fixed by resetting the ECU, it would suggest it's a sensor issue more than a clogged throttle body, so I think I need to set aside a day where we can first do the multimetre test on the sensor, and then see what that says. If all readings are okay, then it'll be on to the throttle-body.

How would one be able to tell if a throttle cable was sticking by looking at it? I know you can manipulate it from under the bonnet, but I'm not sure how you would replicate the situation where it would stick?

All of your advice has been very helpful and I appreciate your time! Once this issue is sorted I'll then investigate the heated seats (I have a sneaking suspicious that none of them work - the front two definitely don't)...hopefully this is a blown fuse rather than all of the elements being broken as I know that the former is an easy fix and the latter means I'll have to accept the car has no heated seats!

It's nice buying a car for £920 - the engine (once warm) and interior is worth that alone :).

CptYossarian · August 16, 2015

CTS = coolant temp sensor have a look at this thread http://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/377171-diy-coolant-temperature-sensor-change-pics.html

Terribly sorry for coming across like a complete moron, but is it possible to get to the stage where you can access the sensor, without removing any bits that would prevent the car from turning on and working?

That's the only way we're going to be able to do the multimeter test.

As far as I can tell they only remove some plastic covers to reveal the sensor so this shouldn't stop the engine from being turned on.