CHO SHU PUI DANNY
Post Number: 23
|Posted on Saturday, 11 January, 2020 - 12:57:
Jim. Could you please introduce me the use of EHA, and how should I test it?
Also, could you suggest good fuel injector cleaner for me please?
Post Number: 99
|Posted on Monday, 27 January, 2020 - 00:32:
Where you removed the copper nut is the right place for the CO measurement. Your result is terrifying. The culprit could be a faulty EHA or false air drawn in.
Run the engine and drive the car until the engine is warm. Remove the plug (two cables) from the EHA. The engine should continue to run unchanged. When the engine is warm it does not matter whether the EHA is connected or not. The warm engine does not need the EHA when idling (and even on normal driving).
The EHA is required to enrich the mixture. The cold engine needs a richer mixture while the warm engine needs a much weaker mixture. And on hard acceleration is also a richer mixture required. This is done by the EHA.
You can test the EHA pulling off the plug and connecting an ammeter: A pin on the EHA is connected directly to the corresponding pin on the plug. Between the other two pins (one on the plug, one on the EHA) you put your ammeter. With the engine warm no current should be measured while idling. When warming up the cold engine you observe a current of maybe 100 mA when the engine is completely cold. The current slowly drops down to 0 mA when the engine is warm. If a current is displayed while the engine is warm, something is wrong. Finding the mistake is difficult because there are a hundred options. The most common is false air that is drawn in somewhere. The error 2121 that you mentioned in another thread also indicates this. If there is false air drawn in the engine ECU tries via the EHA to correct that by enriching the mixture.
The complete graphics showing the behaviour of the EHA while the engine is warming up you can find in TSD 4737. Turbos and non-Turbos do show a different behaviour.
Hopefully I could help,
regards - Udo
Post Number: 100
|Posted on Tuesday, 28 January, 2020 - 08:52:
Perhaps I should mention that the most important input for the engine management to control the EHA is the temperature of the coolant. It is therefore crucial that the coolant sensor works properly. If it delivers incorrect values - electrical resistance in ohms - the engine management system controls the EHA incorrectly. The coolant sensor must report approximately 3000 ohms when the engine is cold, while it only reports 250 ohms when the engine is warm. With a warm engine and 2500 ohms the engine management "thinks" the engine is cold. It may then enrich the mixture considerably, so that the CO value becomes much too high. The picture shows the relation between temperature and resistance.
The resistance is measured with the plug off the engine management (ignition off) and connecting a voltmeter (set to DC voltage) to pin 3 (yellow/blue) and pin 8 (black/slate). If the engine is cold (after a night break), the value should be around 3000 ohms, after a journey (around 80 degrees Celsius) around 250 degrees Celsius, see graphic. If this value is incorrect, the sensor must be replaced. Possibly this is the reason for your much too high CO value.
If possible, do not measure at the front of the plug so that the contacts are not damaged. It is better to remove the cable protection from the plug and measure there at pins 3 and 8.
Regards - Udo
CHO SHU PUI DANNY
Post Number: 25
|Posted on Tuesday, 10 March, 2020 - 01:21:
Thanks a lot for your precious information! I have been working on the car these few months. The car have shown positive and good sign.
I will keep you updated, if there is any new situation.
The VIN of my car is SCAZS02A5PCH46132.
Udo, I have read the post from you on other thread initiated by me. Is aforementioned IDLE SWITCH the same with throttle switch? or preferably could you please indicate the location of IDLE SWITCH to me?
CHO SHU PUI DANNY
Post Number: 27
|Posted on Thursday, 09 April, 2020 - 22:46:
Thanks Udo for the help. After studying the workshop manual, I am now confident to perform the checking you suggested.
I got the engine temperature from thermostat housing with thermometer gun, and the result from coolant sensor are as follows:
when 21 degree celsius = 2430 ohm
when 27 degree celsius = 1971 ohm
when 83 degree celsius = 290 ohm
However, I feel there is something wrong from EHI. It is because when I cold start the engine of 27 degree celsius, the current of EHI has 5~6 mA. After running for 10 mins with temperature rising, the current of EHI slowly drops from 5~6 mA down to 3~4 mA. After 30 mins with operating temperature of 83 degree celsius, the current of EHI surprisingly rose from 3~4 mA to 6.6~10.2 mA, instead of 0 mA per your suggestion.
Is it a problem with EHA or ECU? Could you please advise how should I troubleshoot it?
Thanks a lot for your input again.