Help – Misfire & glowing Cat
Discussion
This weekend I replaced all 8 spark plugs plus new extenders and new lead cables. Despite replacing the cables one by one the result is very rough idle and probable misfire and after a minute or so idle the RH catalyst was glowing translucent.
On the basis I replaced them individually incl all plugs plus coil to dist cable what else may typically be the cause? I have not driven it.
One difference I noted when looking at Steve Heath is the arrangement of the corresponding leads to the distributor as shown in the ‘bible’. As these were taken from a Range Rover Haynes manual how accurate are these, can they be relied on and is there a possibility I could have crossed one of the wires over as there are two which do not correspond to the diagram. The reaction from the cat due to this misfire, is it likely to have damaged the cat?
Any help appreciated
On the basis I replaced them individually incl all plugs plus coil to dist cable what else may typically be the cause? I have not driven it.
One difference I noted when looking at Steve Heath is the arrangement of the corresponding leads to the distributor as shown in the ‘bible’. As these were taken from a Range Rover Haynes manual how accurate are these, can they be relied on and is there a possibility I could have crossed one of the wires over as there are two which do not correspond to the diagram. The reaction from the cat due to this misfire, is it likely to have damaged the cat?
Any help appreciated
If you did them one at a time, there should be no possibility that you have one of them wrong. But the firing order in the 'bible' and in the Haynes manual are both correct. Having two leads swapped into wrong positions could cause exactly this kind of problem. Refit the leads according to the published firing order: 1 8 4 3 6 5 7 2.
The order is what matters.
Make sure you have got the cylinder numbering right. The odd bank is the one on the near side of the car i.e. the passenger side if you have a normal right-hand-drive car. #1 is at the front of the odd bank (i.e. closest to the front of the car), #7 is at the back. Similarly #2 is at the front of the even bank and #8 is at the back.
Follow the HT lead from #1 plug up to the distributor. Make a note of which of the terminals on the distributor it is, because it's important that you can find this one. A bit of tape stuck on the top of the HT cap makes a convenient temporary marker.
Looking down on the distributor, work round it clockwise starting from the #1 lead, and make sure each lead is connected to the right numbered plug.
The correct order is 18436572.
It's possible to put the engine together so that the #1 lead is in different places on the distributor so you can't rely on the absolute position of each lead being the same between cars, but the firing order is absolutely guaranteed to be the same.
If the order is correct, then the only other way for the leads to be fitted correctly is for them all to be out by one or more positions. If this was the case the engine wouldn't run at all, so you know that this isn't the case.
Make sure you have got the cylinder numbering right. The odd bank is the one on the near side of the car i.e. the passenger side if you have a normal right-hand-drive car. #1 is at the front of the odd bank (i.e. closest to the front of the car), #7 is at the back. Similarly #2 is at the front of the even bank and #8 is at the back.
Follow the HT lead from #1 plug up to the distributor. Make a note of which of the terminals on the distributor it is, because it's important that you can find this one. A bit of tape stuck on the top of the HT cap makes a convenient temporary marker.
Looking down on the distributor, work round it clockwise starting from the #1 lead, and make sure each lead is connected to the right numbered plug.
The correct order is 18436572.
It's possible to put the engine together so that the #1 lead is in different places on the distributor so you can't rely on the absolute position of each lead being the same between cars, but the firing order is absolutely guaranteed to be the same.
If the order is correct, then the only other way for the leads to be fitted correctly is for them all to be out by one or more positions. If this was the case the engine wouldn't run at all, so you know that this isn't the case.
Possible one or more leds to dizzy cap, leads to extenders, or extenders to plugs not clipped on fully. Are all the plug nipples screwed on tight? Did you replace leads/extenders with like-for-like? If you have non-resistive leads and extenders you could have problems, or resistive plugds, leads and extenders for example.
Thanks for the replies
Is the CAT likely to be damaged ? i didn't drive it as i could hear all was not well, but left on idle for a couple of mins until i saw the cat became glowing hot & switched off
All connections are very secure & tight - triple checked . I used Magnecor KV85 and new extenders from ACT (identical to those removed)
I did note the connection was slightly different to that shown in the bible whereby leads 6 & 8 were different connections on the distrbutor than shown by Steve Heath which may be the reason.
I'll check yopur suggestions when i return tonight.
Is the CAT likely to be damaged ? i didn't drive it as i could hear all was not well, but left on idle for a couple of mins until i saw the cat became glowing hot & switched off
All connections are very secure & tight - triple checked . I used Magnecor KV85 and new extenders from ACT (identical to those removed)
I did note the connection was slightly different to that shown in the bible whereby leads 6 & 8 were different connections on the distrbutor than shown by Steve Heath which may be the reason.
I'll check yopur suggestions when i return tonight.
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