Coolant sender and sensor

[Mr Ponkerson]

My 97 mk3  ls400 is still running like poop.  Just had the capacitors replaced in the ecu, but have a feeling this will not resolve the issue.

My next port of call will be the above as it runs much worse once warm (vacuum pipes checked, new plugs n leads, throttle body cleaned, exhaust fixed, maf unplugged to check - stalls)

My question is, are normal motor factor parts like ecp good enough or are they really an oem replacement only option.

[Mr Ponkerson]

Just to add to the above, ecu now in - still rough idle (that gets worse as it warms up) and really hesitant and misfiry under load (if I bury the throttle it just bogs down at about 1500rpm).  No error codes bar the Battery one for abs (code 41).  Starting to get really fed up and might just scrap the thing as I'm getting fed up of under 15mpg and spending money on non-fixes.

[Texas]

Not an expert on the LS, but from what you have changed already covers most of the normal causes of possible sluggish running.

But one thing that comes to mind is the fuel system, has the fuel filter been changed recently as a dirty/restricted fuel filter will cause flow problems especially when under load or when accelerating.

paul m

[Malc]

have you changed the air filter ?

Malc

[Texas]

If any sensor ( ie coolant temperature) was faulty or outside of normal limits then I would expect it to show via OBD. But having said that a coolant temperature sensor is in effect is only gonna feed the ECU with info so it ( the ECU) can trim the engine fuel requirements (think old fashioned Choke)

exsisting sensor might be able to be tested to see if it is within spec in situ.

out of interest what device/software are you using to interrogate the ECU?

paul m.

[Mr Ponkerson]

Cheers guys, had a full service done (maybe not fuel filter though, will check).  Goes better at part throttle and higher revs, so will look at fuel filter too.  Using the old wire across obd terminal trick and reading flashes on dash.  The reason for coolant thinking is the gauge barely works (sometimes not at all).  It's never really worked, only occasiinally coming off the bottom and never much below the lowest gauge line. The car wasll ok before the service with a slight misfire every 10-20secs while idling, things started going really funny a week or so after the service.

[The-Acre]

I'd replace the CTS and not worry about it being an OEM part.  Straightforward enough.

[Mr Ponkerson]

Thanks, am getting both sensors done on Wednesday 

[steve2006]

On 9/3/2018 at 1:16 PM, Mr Ponkerson said:

Cheers guys, had a full service done (maybe not fuel filter though, will check).  Goes better at part throttle and higher revs, so will look at fuel filter too.  Using the old wire across obd terminal trick and reading flashes on dash.  The reason for coolant thinking is the gauge barely works (sometimes not at all).  It's never really worked, only occasiinally coming off the bottom and never much below the lowest gauge line. The car wasll ok before the service with a slight misfire every 10-20secs while idling, things started going really funny a week or so after the service.

Bear in mind there are 2 coolant temperature senders, one for the ECU (usually has a green connector) and one for the gauge.

[Mr Ponkerson]

Yep - getting both checked and done.  I'm also going to.put a list together of.other possibilities:

Coils (doubtful as I unplugged one today and the revs dropped significantly, but worth checking)

TPS

IAC

wires behind left hand boot lever

Injectors

Maf (although if it's unplugged the car stalls)

Cooked and blocked cats

Lack of sacrifices to the LS god

 

Feel free to suggest anything you think I may have missed.  Biggest frustration is the lack of CEL and/or codes

 

[cornershop]

TPS could be a good one to prioritise, especially if its better at part throttle?

[Mr Ponkerson]

well, sensors did naff all and the TPS adjustment just made the revs go way too high or low apparently.  Boot wiring and general wiring check next.  Still runs much better before it warms up apparently.  Time to start shopping for something else though methinks

[cornershop]

This is must be very frustrating - it was running fine before the major service, IIRC?

The only other sensors are the cam or crank position sensors - i can’t if these cars have both or just one

Maybe worth try calling a different specialist for a second opinion - eg https://www.japex.co.uk/

[Mr Ponkerson]

Thanks for the advice chap, I'll give them a bell after I get confirmation on whether my "the man" has found anything in the wiring or injectors.

[cornershop]

I was thinking this sounded vaguely related: https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/435341-what-happens-if-the-camshaft-position-sensor-goes-bad.html

As mentioned I’m unclear if these cars have both cam and crank position sensor

Could it be something got dislodged when the service was undertaken.

[cornershop]

There is a cam sensor test pdf in the above link which appears temp related - could be related if yours is worse when warm.

Note also it says if it was the crank position sensor, the engine would spin but not start

[Mr Ponkerson]

Thank you again sir - one more for the list and some more hope for future barging.

[The-Acre]

This must be driving you nuts.  At least you know the sensors you've replaced won't let you down!  We're all waiting to celebrate with you when it's finally sorted. Have you taken it to a main dealer for a diagnostic?  The OBD diagnostic tools you can buy are ok but I don't think they can work as well as the real thing.  Does Toyota's Techstream work on a 97 car I wonder.  A Toyota dealer may charge less if so.

[Mr Ponkerson]

Thanks chap, I haven't as yet - I've been using the wire across the obd terminal trick.  The lad that's working on it has a work mate who thinks he may have an old reader at home so they're going to try that.  I may have to bite the bullet and take it to Lexus for a reading though as I believe most obd readers can't read the old pre-obd2 Lexuses (lexi, lexopodes? Not sure what the group noun is).  I'm fortunate in having a very helpful client who doesn't use his car much and, as such, lends me it Mon-fri.  I'm starting to feel like I'm taking the P now though.

[Mr Ponkerson]

Sorted!

In the interest of completion for any future searches (a lot of threads I found had no conclusion), the issue turned out to be knackered dizzy caps.  This also took out one of the coils so they've been replaced too.  Happy man!