cold running Vrs hot running power drop.

[sheepers]

hi all,
this is my car.


and this is its engine.


the engine in the picture has a nasty habit of dropping about 30-50 horse power when it goes from cold to hot running.
how do i know this?
well, the drop in power is substantial enough for me to feel it without any question. it does the same thing with both a factory computer (40 40 40 crown majesta) and a sard analyze aftermarket job.

how do i know it only does it when it goes from cold to hot?
well, the revs drop, as they do when the thermostat opens and it changes from Mister hyde, to the unassuming doctor jekyll.
so, why?? can you shed some light on this problem??
its an arse to know i only have a few meters of full powers before it all turns to shit.

help?

 

[spf_lexus]

Maybe the ECU is running super rich at startup to heat the catalysts?

 

[ihiryu]

coolant temp sensor, they tend to go bad, and force the car to think it's 250 degrees F.

A way to test it is to unplug it completely, after the car has warmed up. What computer are you using?

 

[sheepers]

it does the same thing with both the stock computer and a Sard Analyse plug in style one.
ll check out the temp sensor and see if its working.
thanks guys.

sheepers.

 

[sheepers]

what values should i be seeing from the temp sensor?
im guessing it varies resistance as the temp changes?

thanks!
sheepers.

 

[sheepers]

ok, i measured the two temp sensors on the water bridge directly under the throttle body side coil.
at 45 degrees C the brown one measured 55 ohms and the green one measured 700 ohms.

having no idea what each one is for and what value it should be i dont know what, if anything, is wrong.
anyone shed some light on what they do and what i should be seeing?

thanks!!
sheepers.

 

[bigdaddeywalt]

did this fix the problem?, because I have the same issue, as soon as the idle drops to 680 rpms, and I full throttle it, it seems to bog. Thanks in advance.

 

[sideshow]

Y the fk does everyone go for the coolant temp sensor
I've never had to change one
Get a pinout of yr ecu
Find the coolant temp sensor signal wire then test voltage
Somewhere near 4 to 5 v cold
And somewhere near .7 to 1 v when hot
Strange y 4 people having cold and hot issues I doubt all or even
Any will be coolant sensor related

But u need to get workshop manual and go thru their instructions
Because testing at ecu pins first saves a fking shitload of time and
Wasting money on changing sensors just because someone inexperienced
Said replace temp sensor

Anyway any workshop manual that does Toyota motors in similar
Era should have similar ways of testing sensors
Plus toyotas are pretty good as a temp sensor on a 4 cyl should have
Similar values to a 1 uz

 

[Beezer]

Always worth testing the o2 sensors too, especially if you're not using the factory exhaust manifolds. http://www.lextreme.com/forums/showthread.php?t=14008

 

[bigdaddeywalt]

well we have checked just about everything, done the resistance check on all the components as lexus stated on their service hints. The only thing we have found out of whack has been the coolant temp sensor which I just checked today. We have tested the MAF, TPS, coils and igniters, fuel lines are new, fuel pump is new and all lines are cleared. Everything else has come up within specs.

One thing that we noticed was after this engine not running after 5 years is that she cranked right up but a couple of injectors were stuck and by tapping them they began to clear up. As of today she idles great and revs cleans but if you fully press the gas pedal instantly, it seems to choke or bog.

Im assuming thats its going into limp mode but we are going to replace the injectors with some we have laying around and see what happens.

 

[bigdaddeywalt]

Always worth testing the o2 sensors too, especially if you're not using the factory exhaust manifolds. http://www.lextreme.com/forums/showthread.php?t=14008

We have custom made headers but using the stock 4 wire sensors up front so i doubt that will be an issue, great post indeed tho.

And im sorry for jacking this thread , id figure this will help out alot of people, thanks in advance.

 

[Bushwhacker]

hi all,
the engine in the picture has a nasty habit of dropping about 30-50 horse power when it goes from cold to hot running.
how do i know this?
well, the drop in power is substantial enough for me to feel it without any question. it does the same thing with both a factory computer (40 40 40 crown majesta) and a sard analyze aftermarket job.

how do i know it only does it when it goes from cold to hot?
well, the revs drop, as they do when the thermostat opens and it changes from Mister hyde, to the unassuming doctor jekyll.
so, why?? can you shed some light on this problem??
its an arse to know i only have a few meters of full powers before it all turns to shit.

help?

Maybe the air filter needs sheilding from the engine heat?

 

[BlackUZZ31]

the stock ECU sucks!

once it warms up it just dumps all the fuel in even sooner and you get this:



I fixed it with this:



and got an extra 10 kw ALL the time (170rwkw - would of got more with the stock AFM removed) rather then 10 mins of 160 followed by 140

 

[bigdaddeywalt]

well we double checked the resistance on the tps signal in the ecu plug and noticed the ohms were low, we installed another tps and seems alot better but havent had a chance to drive it since we need to address a couple of other issues with the car to get it on the road again.

Sheepers hope this helps and by the way your car is very beautiful!

Ill keep you posted to see if this helps, it definitely doesnt bog down anymore but it has a slight misfire if full throttled, kind of like too much fuel at one time and not burning it all.

 

[bigdaddeywalt]

we found the issue, car had been sittting for 5 years and the fuel line inside the gas tank was rusted and when we would full throttle it , it would not give it enough fuel so it would go lean and into limp mode. Fixed that issue, changed the 5 year old plugs, caps and rotors, and GOOD TO GO! Thank god.

Sheepers, i hope your issue gets resolved but figured I post up here to give you some kind of insight as many people dont post up once theyve figured out their issue.