Gen 5 3sge Oxygen Sensor

[jimbob1975]

Hi All,I have a uk spec 1990 3sge celica gen 5.

Does this model have an o2 sensor?

There is no where in the down pipe for one to fit, but there is a plug connector for one?

My car has been like this since I got it but no codes on the ecu?

Ay suggestions? :(

[GT4 BOOSTER]

give these guys a quick call just to make sure.

http://www.justlambda.co.uk/

[mikeb]

No, the UK gen 5 didn't have an O2 sensor or cat until ~92/93.

Not sure why you think you have a connector for one though. I am pretty sure the ECU doesn't have wiring into the O2 sensor inputs, and I don't think it is set up to use one even if it was wired up.

There should be a mixture adjustment pot in the engine bay (on the LH side of the bulkhead, near the MAP sensor and ignitor). Although you probably don't want to adjust it unless you know what you are doing.

[GT4 BOOSTER]

is this the "i want to run on a different ron fuel switch " ???

[mikeb]

is this the "i want to run on a different ron fuel switch " ???

←

No, it doesn't affect timing (that's done by rotating the dizzy). It is for setting the base line fuel mixture on cars without lambda sensors. The usual method of adjustment is to turn the pot at idle until the emissions are within spec (using a probe up the exhaust). Fueling should then be correct throughout the rev/load map.

[jimbob1975]

Thanks for the replys! I know what the pot is you are on about on the bulk head,I will leave alone until it has been through the MOT and see what the emission results are?

Somebody said that the rough idle could be because I have the wrong plugs fitted and as a result a wrong plug gap giving me a rough idle!

Will check em at weekend!

If anybody needs any info on changing a headgasket on one of these let me know as I have just done one on mine.Let me tell you it was a complete B*****D of a job,but saved misen about £600. :o

[mikeb]

It is highly unlikely that the mixture will need adjusting, or that it's the cause of your idle problem.

Wrong plugs could be to blame (but unlikely, unless the gap is huuge). It's more likely to be an air leak on the inlet side somewhere, especially if you've just had it all in bits. Check all the hoses are back on correctly etc.

I've done the headgasket on mine. It wasn't that bad a job, but I agree it could be easier I guess.

[jimbob1975]

Hi Mikeb,I have done about 100 miles since the headgasket, would you say I would need to get the torque wrench out again and see if the head bolts want nipping down again?

I used new bolts and tightened down to correct spec.

Just wondered if the gasket and head may have bedded down a bit.

What do you think?

I will check for vaccum leaks but all hoses are well on and in good condition.

Also I used new gaskets for the inlet manifold that came with the headgasket kit.

How does the idle control valve work in simple terms?

Cheers James :)

[mikeb]

Hi Mikeb,I have done about 100 miles since the headgasket, would you say I would need to get the torque wrench out again and see if the head bolts want nipping down again?

I used new bolts and tightened down to correct spec.

Just wondered if the gasket and head may have bedded down a bit.

What do you think?

I will check for vaccum leaks but all hoses are well on and in good condition.

Also I used  new gaskets for the inlet manifold that came with the headgasket kit.

How does the idle control valve work in simple terms?

Cheers James  :)

←

If you have done the head bolts up to spec (set torque + 90 degrees overtighten), then they should not be re torqued.

What speed is your idle at? Does it do the fast idle (1800 rpm) on a cold start and gradually go down to ~850 when warmed up? If so, your idle control valve is working OK.

The idle control valve is not easy to explain, but basically it's a variable position solenoid with two coils. They are driven with a high speed pulse width modulated signal from the ECU. So 100% cycle on one coil (0% on the other) is fully open, and 50% on each is half way etc. Idle speed is under closed loop control of the ECU and cannot be adjusted. The ECU learns the engines idle behaviour, and stores it, but this information is lost when the Battery is disconnected, and it has to relearn. This could be the reason for your idle problem (but it should be steady again in half an hour of driving).

The only thing you can do to check the idle control valve is not causing the erratic idle is to unplug it with the engine running. Do this with it warmed up, cause it will struggle to keep running otherwise. The idle speed should be about 1000 rpm with the valve unplugged. If it is significantly higher, you have an air leak somewhere. If it is still erratic it must be caused by something else.

Can you describe the idling problem in more detail? Is it always there or intermittent? Does it do it hot, cold, both? Does it drive OK above idle speed?

It could be down to many things including:

Dodgy HT connection (HT cables/dizzy cap/rotor arm)

Dodgy injector connection

Ignition timing (you did set the dizzy in exactly the same place, or have checked the timing properly?)

Cam timing (but i doubt it).

My guess is still with an air leak though.

[jimbob1975]

Thanks for info about head bolts will leave alone.

Now the idle!

Start from cold and it revs at 1000rpm.Set off driving and as soon as you come to a junction and dip the clutch it lopes down to about 500 and is trying to stall!

As it gradually warms up it gets slightly better and once warm with temp gauge slightly below middle fididle it is ticking over at 900 rpm, but rough, as if it has a lumpy (tuned) camshaft.Touch the throttle and from 1000 rpm up it is smoothish.

In traffic when coming on and off the throttle the idle becomes up and down between 500 and 1000rpm,but give it some welly when moving it becomes more stable again.

Pulled the plug off idle control valve and it went up to about 1200 rpm.

Timing is spot on, and tps is set according to manual.

Although. The idle screw is at its slowest it will go, which seems strange?Also the car has a smell of rich fumes all the time and when it gets hot it gets a bit un-responsive and woolley if you know what I mean. :(

[jimbob1975]

Oh Another thing!

I got some spark plugs for it a while back and the guy said do you want the expensive ones or normal ones and being silly I said the dear ones.

The ones he gave me have a fine point on the electrode but did not make a difference when I put them in about a month ago! ;)