Weird idle issue when warm

[Laurens PNut]

Ok, i'm having a very very VERY hard time getting my 1992 SW20 3SGE rev2 through the idle emission because of high CO.

Compression was good, lambda was OK, spark plugs are changed, all fluids are fresh.

Toyota dealer advised to replace MAP sensor and the flex-pipe was leaking.
Replaced MAP sensor but didn't pass.

Recently replaced the flexpipe and now the complete system is air-tight but ever since (today) I experience a rough idle and I can hear a hissing noise trough the cone filter. Just as something is trying to get it to suck in more air to keep it going or something.

Car is running fine. Issue seems not that big when cold.

The idle air screw is all the way in. We adjust the TPS without any luck. I did notice that when turning the TPS the values would jump a bit, don't know if you should be able to read the numbers in a logical order or not.

Also cleaned the TB inside out.

Before it will be at the dealership again I'd like to get some more clues.

There are not codes in the ECU (they were after trying to test without the TPS and MAP connector for example).

Im clueluess.

[Peter Gidden]

The resistance of the TPS wiper should increase/decrease smoothly on a ohmeter when turned in either direction. We use an analogue ohmeter for checking TPS wiper since needle movement is better to see than digits on a digitial meter.

The switch in the TPS needs to be adjusted accurately as per BGB.

[Laurens PNut]

Yeah, we did that with a Fluke digital ohmmeter but like stated I felt the numbers were bouncing around a bit while turning it very very gently so I guess that would be the next fix.

I'm starting to hate this car.

Fix one issue, something else pops up...

[Laurens PNut]

Just did some more testing. Warmed up the car, checked the timing. 10 degree (stock) so thats good.
Checked ECU for codes again > no errors
Issue still occurs, but only as soon as the idle rpm adjusts itself to under 1000 rpm the problems starts.

If I play around with the TPS sensor while the car is running I can make it stall by turning it all the way down, and by turning it all the way up it keeps running. Obviously not smooth but I can control the idle behaviour this way. So that, combined with the fact that the problem only really exist s below 1000 rpm and because there are no error codes i just think the TPS sensor is worn out.

Anybody that agrees?

[bobhatton]

Just did some more testing. Warmed up the car, checked the timing. 10 degree (stock) so thats good.
Checked ECU for codes again > no errors
Issue still occurs, but only as soon as the idle rpm adjusts itself to under 1000 rpm the problems starts.

If I play around with the TPS sensor while the car is running I can make it stall by turning it all the way down, and by turning it all the way up it keeps running. Obviously not smooth but I can control the idle behaviour this way. So that, combined with the fact that the problem only really exist s below 1000 rpm and because there are no error codes i just think the TPS sensor is worn out.

Anybody that agrees?

No

There is a switch on the TPS that puts the ECU into closed loop, you have checked that as per the BGB?

You need to check the air flow meter, most of the times it is that giving problems.

[Laurens PNut]

But I already replaced the MAP sensor...

[bobhatton]

But I already replaced the MAP sensor...

On a Rev2 the MAP sensor just works the boost gauge and fuel cut

[Laurens PNut]

Where the f*ck is my mass airflow sensor then? Where should it be located?
I have a JDM 3SGE N/A rev2 with a cone filter and afaik the MAP sensor is the only one there is.

I previously owned a Nissan with a MAF sensor so I know what to look for...
Or...do you mean the sensor in the intake tube that is similar to the one located under the hood?? The hard plastic probe-like-thing?

Today I rechecked the TPS values according to the BGB. Fully closed the values are ok and stable. Fully opened the values are ok and stable. But as soon as I use my feeler gauge and measure the 0.50mm and 0.70mm values are fluctuating all around.

I have this with a cheap multimeter and with an expensive Fluke multimeter.

So for now, I still have to replace the TPS sensor to rule that one out.

Could you enlighten me on the airflow sensor?

[bobhatton]

Where the f*ck is my mass airflow sensor then? Where should it be located?
I have a JDM 3SGE N/A rev2 with a cone filter and afaik the MAP sensor is the only one there is.

I previously owned a Nissan with a MAF sensor so I know what to look for...
Or...do you mean the sensor in the intake tube that is similar to the one located under the hood?? The hard plastic probe-like-thing?

Today I rechecked the TPS values according to the BGB. Fully closed the values are ok and stable. Fully opened the values are ok and stable. But as soon as I use my feeler gauge and measure the 0.50mm and 0.70mm values are fluctuating all around.

I have this with a cheap multimeter and with an expensive Fluke multimeter.

So for now, I still have to replace the TPS sensor to rule that one out.

Could you enlighten me on the airflow sensor?

Sorry I was thinking it was a turbo

[Davsurfa]

Are the contacts inside the TPS clean?

[Laurens PNut]

Just removed the TPS sensor and sprayed/cleaned it thoroughly.
I did notice something on the throttle body side, don't know if it's an issue or not but here's a pic:



The other side that whitish spot is not visible.

But again, I noticed that the warmer the engine gets the more obvious the problem is.

[Laurens PNut]

Replaced tps sensor, calibrated it according to the bgb and the problem is still there...

What more can i do....

[Laurens PNut]

Allrighty, got a look at the car today AGAIN.
Problem seemed to getting worse and worse, also hesitation while driving and accelerating from low RPM.

Pulled the spark plug leads off and saw that 3 of them had torn boots.
Then I pulled the spark plugs and 3 of them had a cracked insulator


Like wtf?

Ordered new plugs and a new spark plug lead kit and awaiting results...