overrun?

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
landybird

landybird

New Member
Posts
2,858
Location
Melksham,Wiltshire
is that what you call it when you turn the engine off and it carries on or restarts:confused: well whatever the correct term is , that is the Pigs new party trick:rolleyes: (s3 petrol)
what do i check first?, don't want to be fiddling unnecessarily
 
I've heard that this problem can be caused by a build up of carbon in the combustion chambers. The carbon gets red hot and ignites the fuel/air mixture. Have a look at the plugs to see if they are very dirty. If cleaning up the plugs and setting up the timing properly does not fix the problem, then I reckon the cylinder head needs to come off and be cleaned up along with the piston tops.
 
redhand said:
It can't be dieselling if it's a petrol engine ya numpty:p :D
Click to expand...

Oh yes it can.

The word Diesel merely implies compression ignition, OR ignition by a HOT something but NOT an electric spark.

When a petrol / spark-ignition engine is turned off, the sparks stop, BUT there may be red-hot carbon particles glowing in the cylinder(s) or as is the FIRST thing to check the SPARK PLUGS may be fouled down beside the insulators with hard carbon which is GLOWING RED HOT, and then under compression ignites the next charge of air/petrol, and may stay doing so for quite a while. Hard-carbon-fouled plugs are THE number one cause of "running-on".

The very first thing to do it take out the 4 spark plugs, and either get them properly clean which means using a proper plug-blaster, or fit a set of new plugs OF THE CORRECT GRADE.

TORQUE the plugs in carefully so get to "feel" the corect tightness - here's why:
[FONT=Arial, Helvetica, sans-serif][FONT=&quot] Almost all cars and light commercial vehicles use 14mm spark plugs. If the plug is too loose, it will not be able to dissipate sufficient heat from the combustion chamber into the cylinder head and will overheat. If the plug overheats, pre-ignition and running-on are likely to occur. If the plug is too tight, it may break during the installation or during engine operation[/FONT][/FONT].


In my experience, NGK plugs are the best, then Bosch, then Champion.

This is worth reading carefully.
Spark Plugs


I suggest NGK plugs BP6ES, or Champion N9Y or Bosch W6D / W6D1.



CharlesY
 
Last edited:
spark plugs changed and so far today no running on and starting is much better too, so fingers crossed thats sorted:)
next question, why were the front 2 plugs brown on the ends like i'm told they should be, but the back 2 white:confused:
 
landybird said:
spark plugs changed and so far today no running on and starting is much better too, so fingers crossed that's sorted:)
next question, why were the front 2 plugs brown on the ends like i'm told they should be, but the back 2 white:confused:
Click to expand...

First, are all 4 OLD plugs the same make and type?

It looks possible the two white ones may be a much "hotter" grade of plug than the front two, or they may have been loose in the threads in the head and got too hot that way. White suggests running very hot, for whatever reason.

Otherwise, what you describe suggests a LEAN mixture at the rear two cylinders, but richer (normal?) at the front two. Make sure the inlet manifold isn't cracked or broken on the rear half, that the manifold gasket seems OK, and that the manifold securing nuts are tight.

What make and number plugs did you fit?

CharlesY
 
CharlesY said:
First, are all 4 OLD plugs the same make and type?

It looks possible the two white ones may be a much "hotter" grade of plug than the front two, or they may have been loose in the threads in the head and got too hot that way. White suggests running very hot, for whatever reason.

Otherwise, what you describe suggests a LEAN mixture at the rear two cylinders, but richer (normal?) at the front two. Make sure the inlet manifold isn't cracked or broken on the rear half, that the manifold gasket seems OK, and that the manifold securing nuts are tight.

What make and number plugs did you fit?

CharlesY
Click to expand...

old ones were all same, NGK BP5E, all in there real tight.
slightly pee'd off about the new plugs as when OH phoned local place they said they had NGK BP6ES so he went to get 4 but when he got there the guy gave him DENSO WP20EP-U's and said they were equivalent jap plugs:mad: bloke was a right knob tho because when OH asked about HT leads he said £25 but if OH could get them somewhere else to carry on as he didn't want to 'get involved':mad: ignorant sod, won't be going there again!!
 
DENSO plugs are good too.

I just favour NGK, as I ALWAYS had great results from them.

Depending what the WHITE fouling was, it might be due to OIL BURNING, or a really poor grade of engine oil.

Keep an eye on these new plugs - check them after 500 miles at least.

You might like to see this ...

NGK spark plugs symbol code

So your BP 5 E plugs are

B 14mm thread
P projecting nose electrode
5 a HOT running plug ... maybe TOO hot huh?
E threaded end is 19mm / ¾" long.

The cooler running plug may make a difference. So will not having incandescent deposits on the end of the plug.

Good fix.

CharlesY
 
You must log in or register to reply here.

Similar threads

G
S3 dash - just what is available ?
Replies
6
Views
587
doriz
doriz
B
Restored 1972 Series 2 Diesel not starting
Replies
16
Views
749
Shedload
S
A
Bump steer
Replies
11
Views
336
Brown
Brown
R
Series 3 Very long shot - Trying to track down Dads S3
Replies
5
Views
846
dag019
dag019
S
Where are all my gears?
Replies
4
Views
526
Dopey
Dopey
Back
Top