1UZFE idle too high.

[extractors]

Ok,

My idle on start up is about 1350rpm, hot or cold it doesn't move from there.
Just idles fast regardless. Does drop back to about 1000rpm in drive.

Things I've tried, clean and inspected ISCV, resistance test according to manual.
Tried 3 different ISCV'S ( these all worked on another car fine)
Tested for continuity between plug and ecu loom of ISCV.
New ecu temp sender, and check for 5 volts, and grounding to ecu
Tried two different TPS's, and set both according to manual.
Cleaned and inspected throttle body, made sure throttle plate was 100% closed
Check for air leaks, vacuum lines etc
Checked for airlocks in cooling system, vacated air through filling port.
ECU reset, check for fault codes.
Have run without iscv connected = idle was worse, and much higher
Without temp sender = no noticeable difference
without AFM, idle slightly lower, but not rough

Occasionally the idle has come back down to around 700 rpm, but not for long then it will go back to its 1300-1400rpm, not surging just steady.

I removed the ecu, checked for anything obvious, it has had new caps about 6-7 months ago, but was perfect after they were done, and no problems prior to either.

Anyway, the car runs perfect otherwise.

Just about over this now though, the only thing I can think of is the ecu has had enough ?? might be the next thing

Brett.

 

[mshawari1]

Disconnect the A/C wire in the ECU.

As I remember its GND activated.. to rise the engine idle speed.

 

[extractors]

yeah, I might give that a try. But do you you think a fault there could raise the rev's at idle that high ? 13-1400 is a fair wack.

I thought it might be a fault in the cold start circuit ?

Ive pretty much exhausted most obvious causes, and now only left with the ECU as a probability.

I was think of just manually setting the idle via the throttle plate, and blocking the ISCV ? not sure how that would work out. It would have no cold start feature, but who cares in QLD, no idle up with AC, but I will just set it a tad higher around 800rpm.

 

[jeremy]

Might not be helpful, but I know in ours the idle wont come down from cold idle if one (or maybe both?) of the O2 sensors aren't plugged in. We had a dodgy plug that came unplugged ...not sure if it would throw a diag code with an O2 unplugged.

 

[extractors]

Hello Jeremy,

I checked the O2 output in the diag port, and they are cycling as per normal, and have never touched them before. Every now and then it will go back to 700rpm, so something intermittent is causing this.

The thing that annoys me, is the car runs perfect otherwise, heaps of power good economy etc. Its just the idle, I tried reducing the aperture of the ISCV hose, but that does zero until you almost completely block it, then the car starts stumbling and coughing.

Brett.

 

[sideshow]

try this
when the idle drops low to an acceptable idle
quickly unplug the idle motor
this will take the idle mtor out of the equation
if the idle still goes hi and fluctuates then it most
probably isnt yr idle motor and u prob have a sticking throttle or air leak

 

[extractors]

Thanks sideshow,

I'm going to have another look at it tomorrow, the car is heading up sunny coast on Friday so hopefully have it sorted somewhat by then.

Just a thought when I disconnect the ISCV should the idle not change ?

Its now quite rare for the idle to ever get to 700rpm, so might be waiting a while.

 

[sideshow]

not sure if the idle motor will move slightly around if it gets unplugged
but with the magnets inside it i pressume it should stay still
i find with alot of sensors that unplugging them sometiems helps with diagnosing
and checking the dfference before and after
since idle motor moves in and out by disconnecting it should rule that out

even if u unplug it at 1000 rpm
if the idle stays at 1000 then u know ifs prob the idle motor or ecu doing weird shit

what ecu is it again
i have a soarer ecu and an ealry ls400 celsior ecu if u want to test em

 

[extractors]

Apologies for the late reply,

Jim, Ive been driving it around now for a month or so with the ISCV disconnected, now its fine when warm, just stalls when cold, Idle is pretty steady though, around 500-600.

Now I guess that rules out any vacumm leaks etc,

Ive tried three different ISCV, and they all behave the same, even ones which I know work from other cars.

The ECU, is a 1992 UZZ30.

I would be interested in trying an ecu you may have.

Brett

 

[sideshow]

I' think I have a sc400 ecu
I'm in Sydney at moment working so if yr down near fun parks inn a week or two
U can drop in and plug it in and see how u go
Anyway pull covers of ecu and see for fkt capacitors
I can repair the if not to bad
I have a couple hundred capacitors for repairing Toyota ecus

 

[extractors]

Jim,

Will prob be around south Brisbane area in a couple of weeks, so hopefully will drop by then.

Out of interest the caps were only done about 6 months or so ago, was great after they were first done.

Brett

 

[extractors]

Just to close this topic,

I was having some faulty TPS symptoms, and was trying to get a new one.

Now, previously I had set the TPS by the factory specs, .4mm, (continuity) and then .65mm (no continuity). But had varying degrees of success, with odd idle patterns, lazy gear shifting, and running rough when AFM disconnected.

Now I reference the following article,
http://www.lexls.com/tutorials/EFI/tps.html

At the botom of the article he points out the Lexls.com method,

Upon following this procedure, my idle is now perfect and all other symptoms have gone.

I'm wondering how relevent the factory specs/ adjustment method are to a 20 yr old TPS, and perhaps just adjusting using the idle method will give better results.

Brett

 

[chobagz]

It’s only been 13 years but has anyone figured this out. having trouble with my 96 soarer sometimes starts up at 1.5-2.5k rpm or just cuts out and won’t hold idle for a couple min. have been playing around with the auto choke but this one is stumping me and my dad only because it does it sometimes. one day it’ll be absolutely fine then next morning 2.5k cold start and doesn’t go down.
Cheers, Charlie

 

[Sudsy]

It’s only been 13 years but has anyone figured this out. having trouble with my 96 soarer sometimes starts up at 1.5-2.5k rpm or just cuts out and won’t hold idle for a couple min. have been playing around with the auto choke but this one is stumping me and my dad only because it does it sometimes. one day it’ll be absolutely fine then next morning 2.5k cold start and doesn’t go down.
Cheers, Charlie

Have you pulled the stepper motor out and cleaned it? Could just be gummed up a bit

 

[ivan129]

Your problem definately sounds like a vacuum leak.
Have you checked to make sure you don't have a split / perished injector grommet.
You could try spraying some WD40 around. If it hits an area where there's a vacuum leak your idle should change.