Astra MK4 Z18XE Erratic Idling

[anonymous-user]

Hi all,

I have an issue with my Astra in which it has erratic idling issues (more of a chugging or a misfire not excessive jumping just twitching but you can feel it through the car, it dips rather than builds); I have previously bought a new mass airflow sensor of fleabay for cheap £20 ish sterling, I have recently replaced the thermostat and I have a small hole on the gasket between the cat and the mid section of the exhaust (soon to be fixed).

I have replaced the oil, oil filter, fuel filter, replaced the coolant coolant, checked that all pipes are securely fitted (no vacuum leaks), cleaned the throttle body, new sparks, checked the fuel injectors (that was a pain!!!) basically a good old service

What I have noticed whilst doing this, the old sparks where chard and slightly oily (a black and sticky substance so I assume oil ...durrr), a slight hole in the exhaust as previously mentioned (which I don't think is a major issue), however one weird thing the car seems to miss fire when warm.

The car runs fine when cold however when it starts to heat up / when the automatic choke goes off ?, this seems to be the problem. The Haynes manual suggests timing belt however Kwikfit (please don't torch me for this) replaced the belt / kit / water pump 15/20k ago so again I don't believe this is the cause. Another thing to note when I hold the rev's at 1k the chugging disappears ?


Another suggestion I read was the EGR valve however I believe the Z18XE doesn't have one from what my googling has suggested ?

I have read that the coil pack also is an issue, Im sure I read somewhere to try this (please correct me if I'm wrong) to take the coil pack out, turn upside down and leave the sparks in it and turn the engine over. However I didn't see any sparks but that said I don't know if the sparks were fully connected as they were just wresting in the coil pack. (certainly wasn't going to hold them in).

Edit: I forgot to mention that my earth strap is currently just "hanging" on and needs crimping and screwing in, I will be doing this today and will update accordingly

Any suggestions would be great cheers!!!


Mods, if it could be left in GG as I'm about to be embarking on a road trip around Europe in the next couple of months so Id like to fix it quite quickly if not no qualms

Edited by anonymous-user on Wednesday 1st February 09:02

[anonymous-user]

A few more updates that might help diagnose the issue....

For a while there has been a tick near the belts of the car Im not sure if it is a kwickfit fail or what to be honest, it appeared sometime after the belt change so I don't think I could blame them. Also I thought it may be the aux tensioner and belt due to the Haynes manual recommended there looked after yearly (cant remember what it exactly said) .... I have bought a new belt and tension-er, but I put the belt under pressure and the ticking still kept on going (this may of caused the engine light) so it may be a screw in the timing belt box ?

I did get the car and spanner symbol from time to time and the good old owners manual informs me that this is an electric fault, so I assume the previous earth strap was knackered I don't think this will appear now since its been fixed.

Also the exhaust has been sealed now.

Only thing I can think is the coil pack, maf sensor or timing belt (going from haynes and other forum threads) but I cant see why it would be these due to the fact the chugging only comes into effect when it goes it warms up ?

there is an engine warning light after I did all the fixes but I didn't have my reader with me at the time, I will find that out tonight.

[anonymous-user]

Right I popped over to a mate of mines tonight who has an obd reader fault code is

P0170 - Powertrain: Fuel Trim Bank 1

Now according this this thread (below) P0170 can be running rich or lean??

P0170 Rich Exhaust C-30
P0170 Lean Exhaust C-30

http://www.astraownersclub.com/vb/sh...d.php?t=229...

This error has appeared before however I put it down to the issue being with the thermostat running to cold and thus the engine running a little rich ?

Other readings I was given on Idle this was outside and standing still for approx 2 mins at -3C outside temp,

Fuel Trim short Term: 12.5% (bank1 12.5%)
Fuel Trim Long Term 11.7 bank 1 11.7
Idle 824 RPM
Fuel System 1 status: closed loop using oxygen sensor as feedback for fuel control
Air Flow Sensor 2.73g/s

Readings on a steady rev

Fuel Trim short Term: -4.6875% (bank1 -4.6875%)
Fuel Trim Long Term 11.7 bank 1 11.7
Idle 2347 RPM
Fuel System 1 status: closed loop using oxygen sensor as feedback for fuel control
Air Flow Sensor 7.9g/s

No both myself and my mate have no clue about these readings however, we thought it might give someone a better idea.

any ideas chaps ?

[aw51 121565]

You might be better posting this on an Astra forum, or a Vauxhall one. I've never had a Vauxhall though, so never indulged in any of them .

I'd also suggest posting on the Car Mechanics forum - there are people on there who know Vauxhalls inside out (they were very helpful in 2004 when my Mum's fella's T-reg Mk 4 Astra estate had an odd problem with the boot not opening at all - one chap went straight to a correct diagnosis , elsewhere on the car ) .

[anonymous-user]

cheers, Ive seen the technical forum for engines I take it you mean that or is there another one Im overlooking ?

[andy-xr]

Not familiar with the engine. Does it have a throttle potentiometer? Might be worth checking voltage on that if it does

[aw51 121565]

knowlesy said:

cheers, Ive seen the technical forum for engines I take it you mean that or is there another one Im overlooking ?

I've not been on for yonks, and - crikey - having just looked it ain't the place it used to be!

But I'd say post on http://www.kelsey-forums.co.uk/cgi-bin/cmm/YaBB.pl... (Diagnostics and Fault Codes); there's even a thread http://www.kelsey-forums.co.uk/cgi-bin/cmm/YaBB.pl... that is vaguely similar to yours in terms of details given which makes me think that is the right place to post .

Or if this brings no joy, have a mooch round some Astra or Vauxhall forums and find one where the members seem to know what they are on about and make diagnoses that result in the fault(s) actually being fixed .

[anonymous-user]

andy-xr said:

Not familiar with the engine. Does it have a throttle potentiometer? Might be worth checking voltage on that if it does

I don't quote know, but I will have a look, cheers

aw51 121565 said:

I've not been on for yonks, and - crikey - having just looked it ain't the place it used to be!

But I'd say post on http://www.kelsey-forums.co.uk/cgi-bin/cmm/YaBB.pl... (Diagnostics and Fault Codes); there's even a thread http://www.kelsey-forums.co.uk/cgi-bin/cmm/YaBB.pl... that is vaguely similar to yours in terms of details given which makes me think that is the right place to post .

Or if this brings no joy, have a mooch round some Astra or Vauxhall forums and find one where the members seem to know what they are on about and make diagnoses that result in the fault(s) actually being fixed .

Cheers !! Ive already posted on astra owners club but sadly had very little feedback.

Edited by anonymous-user on Tuesday 7th February 21:32