95 2.0 16v Auto idle surging

[SamBurton]

Morning all,

currently working with my dad to restore a 95 2.0 auto CDX, we have an odd one regarding idle.

I t had a rather erratic idle which would put the EML on, sometimes it cleared itself and run very well then others it would splutter and struggle.

I removed the Throttle body assy, cleaned all ports, including IACV, it seems better but now the idle isn't erratic but it now surges in revs. the vacuum pipe that comes from the exhaust manifold area, across the front and down to the bell housing seems to collapse when it surges, i am on the hunt to replace the pipe anyway but i don't think this is the issue,

Can anyone suggest anything. i have got an OBD1 lead coming as i do have OPCOM so hopefully it can help me find the fault area, but i know many gurus are better than computers!

[Robsey]

OpCom will not be very useful on a Cavalier.

If you get an engine management light for more than 5 seconds, then a fault code would be stored.

On the Cavalier, you can do a free diagnostic test using the paper-clip method.

There are loads of threads and forums that mention this test.
Even the OpComusers forum.
(I know, I wrote the whole sub-category for 10 pin ALDL vehicles on that site).

The original website was ToppBuzz.

However, we have all the info on this forum too.

Look here -
viewtopic.php?f=70&t=630

And my new updated thread.

viewtopic.php?f=70&t=16896

The weak spot on these is either the Crank Angle Sensor or Camshaft Position Sensor.
I never know which one it is.
Anyway, assuming you have the X20XEV Ecotec engine.

I believe they changed the relevant sensor with one with a different connector when the Cavalier was replaced by the Vectra-B.
So you can get a conversion lead and Vectra-B sensor that cures the sensor issue.

But first, check out that vacuum pipe.
They should not collapse like you describe.
Surging or hunting is a distinct symptom of a vacuum or induction air problem.

[Robsey]

You could try diagnosing as a Vectra-B with the OpCom device.
As said though, anything pre-1997 is not supported, despite being listed.

As you are getting a pre-made lead, I do not need to tell you how to make your own.
But what the hell, why not, it is only 3 wires anyway...

10 pin ALDL A = ground, goes to pins 4 and 5 of the interface plug.
10 pin ALDL F = 12 volts, goes to pin 16 of the interface plug.
10 pin ALDL G = Diagnostic KWP data signal to pins 7 and 15 of the interface plug.

4 (ground) and 5 (signal ground) are linked within the interface.
7 (K line data) and 15 (Wake-Up Hand-shake signal) are linked within the interface.

[Steven715]

I have the same issue it’s ok when cold but when the engine is fully up to temperature it’s not very good mine is an automatic in drive there is no issue. I also cleaned the throttle body and all the ports. I also put a new IAC valve on this stopped the stalling but not the hunting.
On mine I did have an issue with the crank sensor it was the original from1995, the wires was brittle and broke in your hand, unfortunately for me I couldn’t get an original part, Vauxhall wasn’t very helpful in getting one for me I was prepared to pay the £150 I was quoated but then they said they don’t do them anymore, I desperately needed one so I got one of eBay for £15 this initially got me going again with better results to the idle however I did have a start stall on one occasion so far with a flashing EML.

I also have op-com and would be interested in how to connect this up.

The vacuum pipe that your describing is this pipe about half an inch in diameter and goes into a silver cylinder? This pipe that I think your refining to may be the secondary air injection, this system basically injects air into the exhaust manifold to assist getting the catalytic converter up to temperature quickly the fan only runs for about 3-4 minuets on startup anyway that’s out of the scope of this message.

[Robsey]

Opcom is not really suited to cars before 1997 with 10 pin diagnostic (ALDL) socket.

As your CDX is an X20XEV, then you may get away with diagnosing for an early Vectra-B

OpCom has a 16 pin EOBD II plug.
Cavalier is 10 pin (A to K)

An adapter lead is as follows.:-
ALDL pin A (ground) to OpCom pins 4.
ALDL pin F (battery +12v) to OpCom pin 16
ALDL pin G (Kwp data) to OpCom pin 7.

Any other engine, and the paperclip test would be your friend.

For live diagnostics data, you would need Tech 1 or AutoScanner Opel. - Not OpCom or VauxCom.

All the info you need is in my recently updated diagnostics thread.

viewtopic.php?f=70&t=16896

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As a thought, the EML should not flash.
That sounds more like an immobilser issue.

EML is as follows:-
EML is on with running engine - a fault is present.

EML stays on for only 4 seconds after starting - a historic fault was stored within the last 25 runs of the engine.

EML Flashing - Immobiliser / transponder fault

EML goes off immediately upon starting, no faults stored.

[Steven715]

Opcom is not really suited to cars before 1997 with 10 pin diagnostic (ALDL) socket.

As your CDX is an X20XEV, then you may get away with diagnosing for an early Vectra-B

OpCom has a 16 pin EOBD II plug.
Cavalier is 10 pin (A to K)

An adapter lead is as follows.:-
ALDL pin A (ground) to OpCom pins 4.
ALDL pin F (battery +12v) to OpCom pin 16
ALDL pin G (Kwp data) to OpCom pin 7.

Any other engine, and the paperclip test would be your friend.

For live diagnostics data, you would need Tech 1 or AutoScanner Opel. - Not OpCom or VauxCom.

All the info you need is in my recently updated diagnostics thread.

viewtopic.php?f=70&t=16896

----------------------------------
As a thought, the EML should not flash.
That sounds more like an immobilser issue.

EML is as follows:-
EML is on with running engine - a fault is present.

EML stays on for only 4 seconds after starting - a historic fault was stored within the last 25 runs of the engine.

EML Flashing - Immobiliser / transponder fault

EML goes off immediately upon starting, no faults stored.

Thanks Robsey, I will give it a try.