My Cars Gone Ahunting

[jeff400]

Hi there, would anyone have an idea what is happening?

My car a LS 400 '97 has started "hunting". From cold it'll start up quite ok. Then, after a few minutes while warming up it'll start to hunt with the RPM going up n down like a yoyo. If I don't take it out of gear and throttle it up to around 1000-1200 RPM, it'll stall.

Once warm and had a bit of throttle (it seems to help keeping it in 2nd to keep the revs up a bit) and with the engine fully warm the problem seems to dissapear. Giving it a welly full seems to help too but in traffic this isn't possible.

Are there any ideas what is going on?

Many thanks. Jeff

[steve2006]

Hi,

With this problem being temperature related I would 1st check the coolant temperature sender unit and it's associated wiring as it sounds as if it's giving incorrect info to the the engine ECU by telling it the engine is still cold therefore the cold start injector will be in operation and overfueling will occur even though after a few minutes the engine would be getting warm.

[jeff400]

Hi,

With this problem being temperature related I would 1st check the coolant temperature sender unit and it's associated wiring as it sounds as if it's giving incorrect info to the the engine ECU by telling it the engine is still cold therefore the cold start injector will be in operation and overfueling will occur even though after a few minutes the engine would be getting warm.

Thanks for that Steve. Your reasoning sounds like a good place to start. Is there a way to test the temp sender? I'm guessing I'll find the sensor

around or screwed into the rad somewhere. Is that right?

Cheers,

Jeff

[steve2006]

Hi,

Here is a link to assist with the location.

http://www.clublexus.com/forums/ls400-foru...-read-this.html

Cheers.

[jeff400]

Hi,

Here is a link to assist with the location.

http://www.clublexus.com/forums/ls400-foru...-read-this.html

Cheers.

Hi Steve. Thanks a lot for taking the time to dig up that thread ! What an imformative thread it is!

I think that sensor should be included as a regular service item. It seems that important. Also a brezze to change as well.

I did see somewhere in the thread a Toyota part number for the sensor. Perhaps I shoulld go to Toyota and get an OEM? Any ideas on that?

Would you have any links of spare part shops that might be good on Lex parts and that I can turn to for the sensor? Sure, I can surf around, but I'm hoping you've might have some hot links to sites I might never find.

With that in mind, perhaps we need a new thread to collect a list of parts shops from other enthusiasts on this site.

Cheers :D Jeff

[steve2006]

Hi Jeff,

I would go with OEM via a Lexus dealer ask them for discount as you are a forum member, they normally give 10%.

I did try Cheaptoyotaparts once but they were MORE than Lexus!

Cheers,

Steve

[ColinBarber]

The part is probably used on Toyota vehicles as well. May be worth seeing if it is cheaper at Toyota rather than Lexus. It will be exactly the same part, the one you get from Lexus will have Toyota on it.

[jeff400]

The part is probably used on Toyota vehicles as well. May be worth seeing if it is cheaper at Toyota rather than Lexus. It will be exactly the same part, the one you get from Lexus will have Toyota on it.

As mentioned in the link Steve posted. Below is the Toyota part number.

8942220010 $59.13 (retail) $40.88 (discount)

Electrical - Powertrain control - Coolant temp sensor...LS400 1990 - 1994

I'll poke around a bit, make a few calls and report back to the forum.

Jeff