No idle

[961uz4b]

I started my 1uz for the first time yesterday, today after connecting the tacho I noticed it was idling very high, around 1500-rpm and did not drop back down once up to running temp.

I tried crimping the hose to the ISC and it immediately brought the engine back down to around 550-rpm

So i took the ISC off the inlet manifold, sprayed it with carby cleaner and compressed air, then put 12v to the appropriate pins to test the valve as described in the ISC system pdf on this site.

It did not move very much at all, in fact i couldn't even see it move inside but it sounded like it was trying to.

I put the ISC back on the engine and ran it now the motor will not idle at all, you need to hold the throttle open or it dies.

Im wondering if my ISC valve is stuffed or there is a wiring problem. I read on here somewhere that there is a way to test if the ISC is getting power through the diagnostics terminal?

Any thoughts?

 

[961uz4b]

I should also mention it seems to be running very rich, I only have headers on the motor at the moment but there's quite alot of black smoke.

 

[Peewee]

Start with the tips in this thread.
http://www.lextreme.com/forums/showthread.php?t=10816

 

[gloverman]

What ECU?. Who did the wiring?

 

[961uz4b]

Im not sure what ECU I have.

My motor is the facelift version of the 1uz that came out around 1996 that uses a hot wire as opposed to Kaman Vortex Air Flow meter. Looks similar to the early engines, except it had a large plastic cover that fit over the top of the engine and the AFM is plastic bodied. it's also running sequential injection, as opposed to pairs.

I can take a pic of the ecu if that helps.

I had it wired localy, the guy who did it came well recommended and I've seen two 1uz hiluxs he had wired previosuly, and he has done a stack more.

 

[961uz4b]

So after a few tests I discovered no 12v+ going to the ISC, I took it back to the guy who wired it and he had made a mistake. It is now wired up and was working great. However now I have a new problem

I put a thermometer in the radiator, when i start the engine cold it idles around 1000 rpm gradually dropping to around 700 rpm.

When the temp hits about 60 degrees the idle drops right away to the point where the engine is almost stalling.

Could this be another mistake in the wiring to the ISC or should I be looking else where for the cause of this problem?


Note that the engine was running very rich and lagged power when you put your foot down (witch I assumed was possibly the timing belt being out a bit)
but these issues seem to have cleared up since the ISC has been wired.

 

[gloverman]

There needs to be power to the ISC after the ignition has been turned off. This allows the ECU to reset the ISC. Or the bearings in the isc maybe sticky. Being yours is a late engine the isc may not be able to be disassembled like the early ones. Cheers

 

[Peewee]

As above.

The ECU controls the relay that powers the ISCV. When you turn the ecu off the ECU keeps power on the this relay for 5 or so seconds so that the ISCV can return to its 'home' position. Its also why the car will rev to 1500rpm when you first start it.

The problem may also be that the TPS is not set correctly. Not sure if you've checked that yet.

 

[961uz4b]

I'll check that there is 12v to the isc after the motor is switched off.

As I said there is no 1500rpm start up issue anymore because I solved that buy realizing the isc wasn't wired at all

Everything is fine idle wise but at around 60-70 degrees the idle just drops to barely running.

I'm wondering if that around 70 degrees point the isc closes up and the idle is taken over buy the throttle butterfly?

There in alan key type screw near the throttle crank that allows you to manually wind the stop for the throttle butterfly, does this set the idle once the isc has reached a certain temp? Because I moved this screw to hold the engines revs up when the isc wasn’t working so I could move the truck, then wound it right off once the isc was repaired.

 

[Peewee]

Throttle butterfly is not controlled by anything except your foot. And it should be 100% closed at rest. Some people adjust it because the motor doesn't idle properly, but this just screws things up when you try to fix problems.

The engine should go to 1500 rpm for about 2 seconds upon startup, as the ISCV should be 100% open when you start, and it will adjust from there (as it knows its starting point).


It is imperative that the throttle is 100% closed and the TPS IDL contacts are working at this point. With out this you will just confuse the ecu.

 

[961uz4b]

ok i'll make sure it is 100% shut.

The engine does start up at around 1500 for the first 2 seconds, everything is fine until that 60 - 70 degree mark when the idle goes too low

How can I test the tps? or is there anyway to adjust the idle speed once the engine is up 2 temp?

 

[Peewee]

No way to adjust the idle speed. If all the sensors are working correctly, then it will idle.

Have a look at that link I posted above to adjust the TPS

 

[961uz4b]

The throttle butterfly is 100% closed, I've reset the isc and ecu. ive tested the isc and the tps and both are working correctly and getting power. And I still have the problem.

One thing i've noticed is that the motor still seems to keep running if i crimp the supply line to the isc off, although it could be that being a silcon hose im not crimping it hard enough shut, there are no vacume leaks either.

There was speculation that the timing belt may have been put on a little out of time before I got the isc wired, If the motor is still a tiny bit out of time could this be a side effect? How can i test if the timing is correct?

here is a video of the motor running and the problem

www.roberts02.com/problem.mpg.mpeg

 

[XR8tt]

Check air flow through maf. Then through t/body.. If there isn't any ? You have an inlet leak!!
I'm not 100% sure the throttle body closes completely shut either ??

 

[Peewee]

I'm 90% sure that if the timing belt is out one too the ECU will throw a code. The reason I'm not 100% sure is that members have come across this before, but no one has ever said how many teeth it was out when they pulled it apart.

And yes, the motor should start to choke if you squeeze that hose.

Potential leak points are
* brake booster connection point at rear of plenum
* PCV connection point at side of plenum (passengers side)
* injectors not sealing properly
* plenum/lower plenum not tightened down enough

Go around with a hose with one end in your ear and try to hear for the leak.