Miss firing when warmed up?

From the humble 1256 to meaty V8`s, swaps, rebuilds, tunning, etc.

Moderator: Moderators

Miss firing when warmed up?

Postby Goldenbrown » 26 Jun 2006, 08:58

Does anybody have any suggestions? When my Chevette has warmed up it tends to miss fire (running on about two/three cylinders) then clear, only to do it again and again.
Please help....
Goldenbrown
`L` Plate Newbie
`L` Plate Newbie
 
Posts: 34
Joined: 12 May 2006, 11:49
Location: Morecambe, Lancashire, UK

Postby Neilyman » 26 Jun 2006, 09:06

Head Gasket blown between 2 of the cylinders?
That`s what mine was like when the gasket went `tween 1 & 2.
Image
User avatar
Neilyman
Admin and dirty rotten egg!
Admin and dirty rotten egg!
 
Posts: 2834
Joined: 21 Nov 2004, 17:20
Location: West Yorkshire, UK

Postby Doive » 26 Jun 2006, 09:32

If the head gasket has gone, it should exhibit other faults too. When the engine is warming, take the cap off the radiator and check for bubbles rising in the coolant. Also, have a look for overheating or pressurisation of the cooling system. Mine occasionally misfires, but not as bad as you describe. Have you checked the plug type? If they are running too hot then they could drop a cylinder, or if they are too cold they could be sooting up and causing poor running.
<img src="http://sfx-images.mozilla.org/affiliates/Buttons/firefox2/firefox-spread-btn-1b.png">

Med Venlig Hilsen

www.doive.co.uk
User avatar
Doive
Pyrotechnic Nutter Admin
Pyrotechnic Nutter Admin
 
Posts: 4357
Joined: 22 Nov 2004, 18:43
Location: Clinging to a Turbine, Hexham

Postby Neilyman » 26 Jun 2006, 09:50

Doive wrote:If the head gasket has gone, it should exhibit other faults too. When the engine is warming, take the cap off the radiator and check for bubbles rising in the coolant. Also, have a look for overheating or pressurisation of the cooling system.


Only if the Gasket has gone between a cylinder & the water Jacket will those symptoms arise Doive.

Neilyman wrote:Head Gasket blown between 2 of the cylinders?
That`s what mine was like when the gasket went `tween 1 & 2.


If as above, when the plugs fire, they can ignite 2 cylinders together, causing some weird noises & misfires. Sometimes it runs ok, sometimes it runs like a dog. I ran mine for 2 days like that, when I removed the head, it was only a small break in the gasket.
Image
User avatar
Neilyman
Admin and dirty rotten egg!
Admin and dirty rotten egg!
 
Posts: 2834
Joined: 21 Nov 2004, 17:20
Location: West Yorkshire, UK

Postby Goldenbrown » 26 Jun 2006, 11:31

Thanks for the info.

The car uses no water and the temperature gauge always stays below half way, in addition the fuel consumption is bad!!! like 20ish under normal driving.
Goldenbrown
`L` Plate Newbie
`L` Plate Newbie
 
Posts: 34
Joined: 12 May 2006, 11:49
Location: Morecambe, Lancashire, UK

Postby Doive » 26 Jun 2006, 11:42

Could it be running very rich? Does it smoke at all? Look for black smoke when accelerating.
<img src="http://sfx-images.mozilla.org/affiliates/Buttons/firefox2/firefox-spread-btn-1b.png">

Med Venlig Hilsen

www.doive.co.uk
User avatar
Doive
Pyrotechnic Nutter Admin
Pyrotechnic Nutter Admin
 
Posts: 4357
Joined: 22 Nov 2004, 18:43
Location: Clinging to a Turbine, Hexham

Postby Goldenbrown » 26 Jun 2006, 12:45

It does not smoke at all the engine has done 28,000 from new.
Goldenbrown
`L` Plate Newbie
`L` Plate Newbie
 
Posts: 34
Joined: 12 May 2006, 11:49
Location: Morecambe, Lancashire, UK

Postby donlondon » 26 Jun 2006, 18:13

If it misses almost every time it's warm then you could be looking at cracked ht leads or dizzy cap, I had to do just about everything on the ignition side with my car.

It may also be worth compression testing each cylinder as I made the mistake of ignoring a small misfire and seized my engine :oops:

If you get the car up to running temp and when the misfire occurs pull over and pull an ht lead off at a time (remember to insulate yourself cos ignition bites!), each lead should affect the running of the car bar the cylinder that has the problem.

Once you've identified which cylinder the problem is with you can swap that ht lead and hopefully that will resolve your problem.

Fingers crossed for you mate
donlondon
`L` Plate Newbie
`L` Plate Newbie
 
Posts: 39
Joined: 06 Jan 2005, 12:53
Location: London

Postby Goldenbrown » 27 Jun 2006, 09:13

Many thanks for all the advice, i'll get the spanners out tonight!!!
Many thanks.
Goldenbrown
`L` Plate Newbie
`L` Plate Newbie
 
Posts: 34
Joined: 12 May 2006, 11:49
Location: Morecambe, Lancashire, UK


Return to Engine & Gearbox

Who is online

Users browsing this forum: No registered users and 1 guest

cron