1
Omega General Help / Re: V6 rough idle/running
« on: 18 January 2011, 16:59:55 »
Hello World,
Just wanted to share my experiences in case it's of help to another. I originally found this thread using a Google search and most of the info here was of great help.
Having driven the (wife's) car a 2000 Model B 2.5 V6, there was initially no issue, despite her report one during commuting.
I set out to the local accessory shop to get a set of new plugs as these hadn't been changed in 2000 miles, and a set of new plugs are worth their value at the pumps (these days) just on improved MPG.
Having driven the vehicle about 8 miles on a round trip to get the thing through the warm up cycle I stopped for about 2 mins. On restarting the car there was a definite mis-fire, and from the feel of it it was one cylinder on the left side bank (viewed from cabin) The mis-fire was compounded by a more noticeable exhaust note as the unburned fuel from failing cylinder, ignited in the down pipe on the next cylinder's exhaust pulse. This sounded somewhat like a blowing exhaust.
So this may be a tell tale sound for others to listen out for.
Performance and inst mpg dropped off, but no indications from dash light that this was ecu logged fault.
So I stripped down the necessary clutter to change the plugs.
On removing #6 plug (back right when viewed under bonnet) the outer of the plug had rusted and the boot on the lead was covered in a brown dusty rust stain. Clearly water had been entering the plug well and evaporating off causing the deposit on the lead boot.
Yet now the plug was certainly mis-firing. Now not sure how many of you have looked closely at the way a plug is made, but when the insulator part is crimped into the metal base, the plating put on the base cracks off, leaving the crimped part most susceptible to corrosion. If the plug gets exposed to water and heat to exacerbate rusting this crimping swells on the 360° surface surrounding the insulator and it cracks the porcelain very neatly and almost invisibly. This allows for further ingress of water if the contaminant is still present, and the result is a plug that shorts to ground from core to metal base.
Whilst the leads were off I performed the resistance testing of the HT side of the DIS as explained in the video link I found linking from this thread. As all the secondary readings were within spec I was confident I'd located the cause of the misfire.
In this instance replacing the plug(s) cured the mis-fire, but not the cause.
Later that day it rained and on lifting the bonnet I noticed a steady stream of drain water dropping over the #6 plug area and the DIS, and also on the other bank under the scuttle edge. The foam is soaked, and so remedial treatment will be required to solve this issue. The regular rain drain on the offside is unblocked, so I'll need to be creative with the solution to clearing standing water from the lowest point on the scuttle.
Hope that's help to somebody one day.
Just wanted to share my experiences in case it's of help to another. I originally found this thread using a Google search and most of the info here was of great help.
Having driven the (wife's) car a 2000 Model B 2.5 V6, there was initially no issue, despite her report one during commuting.
I set out to the local accessory shop to get a set of new plugs as these hadn't been changed in 2000 miles, and a set of new plugs are worth their value at the pumps (these days) just on improved MPG.
Having driven the vehicle about 8 miles on a round trip to get the thing through the warm up cycle I stopped for about 2 mins. On restarting the car there was a definite mis-fire, and from the feel of it it was one cylinder on the left side bank (viewed from cabin) The mis-fire was compounded by a more noticeable exhaust note as the unburned fuel from failing cylinder, ignited in the down pipe on the next cylinder's exhaust pulse. This sounded somewhat like a blowing exhaust.
So this may be a tell tale sound for others to listen out for.
Performance and inst mpg dropped off, but no indications from dash light that this was ecu logged fault.
So I stripped down the necessary clutter to change the plugs.
On removing #6 plug (back right when viewed under bonnet) the outer of the plug had rusted and the boot on the lead was covered in a brown dusty rust stain. Clearly water had been entering the plug well and evaporating off causing the deposit on the lead boot.
Yet now the plug was certainly mis-firing. Now not sure how many of you have looked closely at the way a plug is made, but when the insulator part is crimped into the metal base, the plating put on the base cracks off, leaving the crimped part most susceptible to corrosion. If the plug gets exposed to water and heat to exacerbate rusting this crimping swells on the 360° surface surrounding the insulator and it cracks the porcelain very neatly and almost invisibly. This allows for further ingress of water if the contaminant is still present, and the result is a plug that shorts to ground from core to metal base.
Whilst the leads were off I performed the resistance testing of the HT side of the DIS as explained in the video link I found linking from this thread. As all the secondary readings were within spec I was confident I'd located the cause of the misfire.
In this instance replacing the plug(s) cured the mis-fire, but not the cause.
Later that day it rained and on lifting the bonnet I noticed a steady stream of drain water dropping over the #6 plug area and the DIS, and also on the other bank under the scuttle edge. The foam is soaked, and so remedial treatment will be required to solve this issue. The regular rain drain on the offside is unblocked, so I'll need to be creative with the solution to clearing standing water from the lowest point on the scuttle.
Hope that's help to somebody one day.