Misfire 1998 1.6litre Ecotec Astra - Crinkly Dave
Friend's car (82k, served by GM and local independent "to the book") has developed a minor misfire recently. Idles like a train, and OK when cold, but once it is hot there is a minor misfire. Sound to me like one cylinder only.
Original thought was petrol added a couole of days ago, but misfire seems on one cylinder, not all
Sadly no manual, so decided to do the basic checks. Plugs were the correct GM double electrode with gaps varying from 35 to 40 thousands of an inch (just under 1mm!). All seemed ok, except the middle 2 were not tightened to their seat by perhaps ¼-½ turn, and one of these had brown marks on the outside of the ceramic where it goes into the metal. Only 1!!
Colour seemed ok on electrodes, but some light carbon on plug base where electrodes attached (possibly due to the mainly 5-10 miles it does a day.
I have suggested 4 new plugs & compression test (in case one valve is sticking or not seating), as this is the simplest and cheapest check before we send it to the local independent to put on his machine.
I am vaguely aware of some GMs having problems with crank sensors, but this is beyond my fairly extensive DIY equipment.
Ideas, if only to confirm correct plug gap. Thanks in advance
Misfire 1998 1.6litre Ecotec Astra - robcars
i fthey are twin electrode then you cant alter gap anyway.

If in doubt try new set of plugs just to confirm or deny suspicion.

But I would guess its likely to be a camshaft sensor (not hard to do) or egr valve. But would be good to get a fault code if there is 1 from the sysytem.
Misfire 1998 1.6litre Ecotec Astra - Crinkly Dave
Car off to independent tomorrow for fault reading. One suspicion (apart from yours) is the coil pack, which someone has suggested is a problem with this model after 50k

Thanks for the help
Misfire 1998 1.6litre Ecotec Astra - Screwloose

Has all the hallmarks of the "normal" £114 coilpack failure - except one. You don't mention if the MIL light is coming on?
Misfire 1998 1.6litre Ecotec Astra - Crinkly Dave
Thank you Screwloose.

Light not mentioned. Would it stay on, or go off if fault cleared? Does the light always come on with this fault.
Misfire 1998 1.6litre Ecotec Astra - Screwloose

As a '98 could be either an Astra-F or G; it's difficult to be definite about the MIL light. On an Astra-G with the integral coil-over-plugs pack, the light will usually come on for a while with a single cylinder misfire code [P0300 to 0304] stored Swapping the plugs around will then show if it's a plug or a position problem; if the returning code stays where it is [firing a different plug] then, if the compressions are OK, it's a fair bet it's another cooked coilpack. [Did two on Astra-G's in two days for the same garage last week. They seem to die in hot weather.]
Misfire 1998 1.6litre Ecotec Astra - Ruperts Trooper
Astra G (Mk4) - if the engine management light is OFF forget analytical diagnosis - there are so many sensors which might give minor fault codes you can regard the engine as running normally.

Normal (twin-electrode non-adjustable) spark plugs should last 40k without problem. Try Bosch Super 4 (520) quad electrode plugs - a bit more expensive but will last "almost indefinitely".
Misfire 1998 1.6litre Ecotec Astra - Pugugly {P}
Could his be an air leak in the pipe that runs from the Air flter to the manifold, it' s a known weak spot on similar engined cavalier, the re-inforced trunking "wears" on the bottom out of sight and needs fingertip examination.
Misfire 1998 1.6litre Ecotec Astra - Dynamic Dave
Or it could be the all too common problem with the EGR valve sticking.
Misfire 1998 1.6litre Ecotec Astra - Crinkly Dave
Thank you to everybody who tried to help.

2 other sources involved. A nice RAC man (whose computer would not speak to Astra as it was pre2000) who said he was 90% certain it was a coil pack, and Car Mechanics article of August 2004 which suggested coil pack was almost a service item after 50k.
Taken to local independent, who have fitted coil pack and plugs and all is OK> Could have reduced cost a lot at Autovaux, but my mate was keen to get mobile again.

Can I thank everyone who helped. Particularly the obvious professionals who bothered to respond. Nice of you to give your time up for free after 10 hours in the workshop.

Fitted new front struts to daughter's punto this weekend. Checked old strut for length fully open, length compressed, diameter, bush diameter etc in great detail (much to local motor factors amusement) then double checked the numbers were the same in both boxes. Wish I had opened the second one, as it had a strut from a Polo in it. Wish I had done this before removing strut from Punto!!

Thank you again, everyone.
Misfire 1998 1.6litre Ecotec Astra - Ruperts Trooper
"coil pack was almost a service item after 50k"

We've two Astras in the family, a 1.6 16v on 77k and a 1.8 16v on 81k, both running sweetly on their original coil packs.

I must watch out for signs of imminent misfire - or perhaps changing the plugs every 40k, as recommended, avoids this sort of expense!

Why can't RAC computers diagnose faults on pre-2001 Vauxhalls? My local independent garage can. There are alternatives to Vauxhall dealers Tech2 without paying £50-60 just for diagnostics. I must remember not to join the RAC!
Misfire 1998 1.6litre Ecotec Astra - Crinkly Dave
Rupert's trooper

But he was correct. BIt of a surprise, as the last time (flat battery) the guy's computer did connect OK.

One of the professionals will be along shortly to explain, perhaps. Wasn't 2000 when the Euro system came in?
Misfire 1998 1.6litre Ecotec Astra - SpamCan61 {P}
>>Wasn't 2000 when the Euro system came in?

Yes I think most VXs up to 2000 can have their trouble codes read via the 'paperclip method' whereas 2001 onwards are OBD2 & need a proper reader of some sort.
Misfire 1998 1.6litre Ecotec Astra - Ruperts Trooper
My local independent garage can read the fault codes on all ages of Vauxhalls - eg for Astra - basic up to '97, Tech2 type '98-'00 and EOBD/OBD2 from '01 on.

My point was - if my local independent can read them, why can't the RAC? Seems to me another reason for just getting a good value recovery deal.

Ask Honest John

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