Opel Astra G CDX (20sel)

Arcticblue

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Apr 2, 2019
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I bought the car (Astra CDX 2l 16v; 20sel motor) from an old man who only drove in once a month for many years. It only has 175 000 on the clock.

Before is start: You can find nothing on Google on this engine (20sel). It is a huge struggle to find sensors for this car. The car has no MAF sensor. It as no Crank sensor. It has no o2 sensor. It is a mix of old and new technology on this engine and works like no other 2.0l Astra G's sensors. I asked 3 other people with the same car and they told me they do not have them either.

Ps. No engine light on!



The symptoms

1.) The first time I started the car I noticed the IACV was not working.

The IACV was stuck on 750rpm. I cleaned it and it is working 100% now.

2.) Struggle to start

The car would start between 2 swings and 4 swings. Does not matter if it is hot or cold.

3.) Not a solid misfire but rather a Lean or rich misfire

  • When you start the car when it is cold it has a very noticeable rough idle.
  • When stationary and you rev the car slowly, the engine runs very rough at 1500RPM when cold.
  • When you drive slow and hit around 1500 RPM the car would cradle gently.
  • When the car is hot it has the same symptoms as when it is cold but you can hardly feel it.

4.) Fuel economy

The car would drive 25km's on a R100's fuel and then 80km's on a R100's fuel.

5.) Power issues

The car runs like a 1600 most of the time. At times it runs as fast as a 1400 but at times like an 1800.

6.) Car would just die while driving once in a blue moon

Sometimes, once a month the car would just die while driving, but just for a second and then run fine again. The engine light will be on for 2 seconds and then go away. At one stage it did it for a week but then went away completely.

What I have done so far but did not sort the issues out

  • Took the car for a scan and showed something was up with the Crank PS. Replaced it.
  • Tested a MAP sensor from another CDX and it made no difference after a week.
  • Did a standard service but no joy.
  • Checked all wires, plugs, earth, power and signal wires with multi-meter and cleaned it all.
  • Compression on car tested out 100%
  • Tested fuel pressure and it tested 100%
  • Used lique molly fuel system cleaner and cleaned injectors.
  • Cleaned fuel injectors manually and observed them while fuel rail out and they are all good.
  • No oil loss, water loss and no mixture.
  • Did a radiator flush.
  • Checked timing, tensioner and belt but it is all fine.
  • Checked for air leaks but no joy.

The coolant sensor saga

This is an odd one. I read on Google and many forums that a coolant sensor can give the same symptoms. I then bought one from Goldwagen but the car ran like a 1400, very light on fuel but the engine ran hot. The misfire was gone but gradually came back again as I drove the car till it was back to normal semi-misfire.

I was told by a car parts salesman that it is the wrong coolant sensor and he gave me an aftermarket one for the engine. This is where it gets interesting: after I installed it the misfire was gone again. I went for a drive and this car had a 2.0l engine power. It had so much power that I could not believe the car was so fast. From low RPM right through to high rpm – it pushed me in to my seat non-stop. BUT, after stopping at the shop and starting it again, it was back to a 1600 engines power and everything else came back (misfire, fuel economy, etc.)

I then bought the Bosch coolant sensor for the car. Same thing happened. First run after installing it the car was super fast and after the second start it was back to normal. The engine has better low end power at times.

Coil Pack

I started the car one morning and the car had a solid misfire. I threw water on the manufold and found piston 1 and 4 is at fault. I tested the coil pack and found high ohm readings on bank 1 of the coil pack but not all the time.

I did not have money for a coil pack at that stage so I took a chance and made the spark plug gap on piston 1 much smaller. Oddly, the car ran like an 1800 engine all the time. Very light miss now and then. I bought a new coil pack, replaced piston 1's plug with one I know is working. The car ran good for a while before all the symptoms came back again.

Extra information

When it is cold outside, the car would run rough and slow. Even if the car is on temp and i've been driving for a while. When the temp is warmer outside it is the same but if the car stood in the sun the whole day it is almost like the car has no issue except it has an 1800 motors power.

The other thing is if the car runs rough in the morning and slow, it will do that even if it is on temp but once the car stood for a while and I start it – the symptoms are almost not noticeable.

What I have not done

Have not replaced ignition leads

Have not replaced TPS

Have not changed intake air temp sensor

Have not replaced timing belt kit

Have not replaced fuel pump

Have not replaced loom or ECU

Before I buy and replace more and more stuff, which takes all my money away each month, I would like to know if anyone has any idea what it might be. It is or that or selling the car which I kinda like and would like to keep.
 

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Last edited:

Arcticblue

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Who is ROUX? Sorry, i'm new here. Someone told me to post this here and see what people has to say. I have spoken to many maccie's and they all are confused and also has no idea what is going on...
 

pinball wizard

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Who is ROUX? Sorry, i'm new here. Someone told me to post this here and see what people has to say. I have spoken to many maccie's and they all are confused and also has no idea what is going on...
Nevermind that. Where's the pics of the car?
 

TheChamp

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The fact that it behaves for a while after replacing some sensor leads me to believe it could be something related to the ECU, have you tried the resetting thing of disconnecting the battery for an hour?
 

TheChamp

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Another thing I forgot, the air sensor on the intake, try disconnecting that and running the car without it and see what happens.
 

Arcticblue

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Apr 2, 2019
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The fact that it behaves for a while after replacing some sensor leads me to believe it could be something related to the ECU, have you tried the resetting thing of disconnecting the battery for an hour?
I have disconnected it a few times but it has the same symptoms. I have actually done it the past weekend and the car is doing the same.
 

Arcticblue

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Apr 2, 2019
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Another thing I forgot, the air sensor on the intake, try disconnecting that and running the car without it and see what happens.
I have done it, engine light comes on when i do it. I'm going to call Goldwagen today and ask them how much a new one will cost. I have tested it by back probing and testing with a multi-meter and it seems to change voltage as the car gets hotter. The intake pipe runs over the radiator so it is bound to let some hot air in on idle.
 

TheChamp

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I have done it, engine light comes on when i do it. I'm going to call Goldwagen today and ask them how much a new one will cost. I have tested it by back probing and testing with a multi-meter and it seems to change voltage as the car gets hotter. The intake pipe runs over the radiator so it is bound to let some hot air in on idle.
I suggested this because it was suggested to me when my Corsa had a misfire and lack of power, the engine light does come on amber to indicate the disconnected sensor, it's not a big deal, just try it and see how it behaves, for some strange reason it made a huge difference on my car although the problem turned out to be a defective coil, I still don't understand why the coil would spring back to life when i disconnected that sensor.
 

Arcticblue

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I suggested this because it was suggested to me when my Corsa had a misfire and lack of power, the engine light does come on amber to indicate the disconnected sensor, it's not a big deal, just try it and see how it behaves, for some strange reason it made a huge difference on my car although the problem turned out to be a defective coil, I still don't understand why the coil would spring back to life when i disconnected that sensor.
Thank You. I will try the disconnection. I'll also test again with the multi-meter. I've been reading up on that intake sensor and it seems it can cause the same issues as the coolant sensor or even cold start switch.
 

pinball wizard

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Is it diesel when it's the CDX.
I don't think the ever made this shape astra in a diesel. The CDX is a CD with extras. Also the OP says 2.0l 16v and the pic is of an ecotec petrol engine.

That said I've never seen a CDX in real life. Seen plenty of CD's, my old man even had a CD.
 

Arcticblue

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Apr 2, 2019
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I suggested this because it was suggested to me when my Corsa had a misfire and lack of power, the engine light does come on amber to indicate the disconnected sensor, it's not a big deal, just try it and see how it behaves, for some strange reason it made a huge difference on my car although the problem turned out to be a defective coil, I still don't understand why the coil would spring back to life when i disconnected that sensor.

I disconnected the air temp sensor. all the symptoms was there but the car felt much-much better. The lean/rich misfire was there but you have to sit dead still in the car to feel it. The power was more stable, a bit more than usual but still had the slow/fast issue. The car is getting a bit hotter than usual but lighter on fuel. I plugged the sensor in and everything went back to normal with the more noticeable misfire. I read up on the sensors and they showed a few ways to test it and all the tests that i did shows the sensor is fine. When i test the ohms and just touch the sensor the ohms would go down. I also read that when you disconnect the sensor the ECU will set itself to read a specific temperature by default.

Since the issues are there but just less noticeable, can it be that the car is throwing more/less fuel which makes less of a noticeable semi-misfire? If a engine runs hot it is usually because of less fuel... this tells me there is a semi-misfire on a plug or injector. In the mornings you can feel an almost constant semi-misfire till the car gets hotter. I know that in the mornings it is cold so the car pushes more fuel because the engine is cold and as it gets above a specific temp the car will throw less fuel. So, cold engine, more fuel, more of a misfire till it gets hot, trims the fuel which causes a less noticeable misfire. This still does not explain why the car is fast and then slow and then light on fuel and then not. It almost seems i have 2 issues. One can be a plug wire and the other a possible injector misfire. The other... i have no idea.
 

TheChamp

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Totally out of ideas, the best you can do is to keep on researching and hope to find the solution.
 

rietrot

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Problems I had with my car the 1600. That might help you. The crank sensor/pickup' timing was off with resulted in a missfire and the car being underpowered.
This was because the pully was warm out and didn't align properly.

The coil is a common issues in these cars and usually at fault when there's some kind of missfire.
 

Arcticblue

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Apr 2, 2019
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The semi-misfire feels constant in the morning but when it is hot the misfire feels like it is misfiring every second to third fire. It's almost feels like a spark jumping every now and then. I think i'll have to clean the injectors cause they are all "clicking" when you listen to them with no skip. If you detach the plug wires from the coil there is no skip in spark. New plug wires.
 
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