420R Spark / Mis-Firing issue
Discussion
Having received my car back from Caterham 420R (2017 plate) from it's 2nd annual service in November I have driven it only 50 miles and it went pop! The service included replacing the spark plugs and the cam gasket as oil had seeped in to Spark plug wells 2 & 3.
When I drove the car a few weeks ago prior to lockdown I was decelerating from around 70/80 mph on the motorway and there was a big pop in the exhaust and it sounded like the engine had blown up. Luckily that wasn't the case but it drove in limp mode and was mis-firing / running on 3 cylinders all the way home....
I did some checks and when I removed the spark plugs I found that Spark plug 3 was knackered (see below). Lack of gap, heavily eroded and looks like a crack in the insulator....
I cleaned up the plug and used some pliers to bend back the plug so the gap was the same as the others and when tested the car run pretty much fine again (although a slight mis-fire on cold start).
Caterham are now in lockdown so I wanted to see if anyone can help me please? Someone mentioned the plug looks like it's been dropped...
When I drove the car a few weeks ago prior to lockdown I was decelerating from around 70/80 mph on the motorway and there was a big pop in the exhaust and it sounded like the engine had blown up. Luckily that wasn't the case but it drove in limp mode and was mis-firing / running on 3 cylinders all the way home....
I did some checks and when I removed the spark plugs I found that Spark plug 3 was knackered (see below). Lack of gap, heavily eroded and looks like a crack in the insulator....
I cleaned up the plug and used some pliers to bend back the plug so the gap was the same as the others and when tested the car run pretty much fine again (although a slight mis-fire on cold start).
Caterham are now in lockdown so I wanted to see if anyone can help me please? Someone mentioned the plug looks like it's been dropped...
- Recommended suitable replacement better performing plugs? Engine is the 2.0 litre Ford Duratec. The standard plug is TR6AP13 but can I buy better NGK ones?
- Should I check anything else that might have caused this problem?
Edited by rgbarker on Tuesday 14th April 15:13
Seems weird that the one plug would go out of spec like that (the blackness on it will be from it running on 3 when you drove home).
I'd replace with whatever the stock plugs are and go from there.
Definitely possible it was dropped or similar - but it takes quite a bit of force to close the gap up like that (agree the insulator could have been broken when dropping but also quite tough stuff). Can you shine a light down the plug hole and see if there is any evidence of plug/piston contact at all?
I'd replace with whatever the stock plugs are and go from there.
Definitely possible it was dropped or similar - but it takes quite a bit of force to close the gap up like that (agree the insulator could have been broken when dropping but also quite tough stuff). Can you shine a light down the plug hole and see if there is any evidence of plug/piston contact at all?
The plug that is recommended mostly is the NGK R BR7EFS. At one time Caterham used to supply cars with this plug, mine was one of them.
Apparently it is less expensive than the Ford plug and has no real downsides. Some say they have used it instead of the Ford plug and their car would stall immediately after starting but that's most likely been down to other things, its hardly uncommon, especially with the standard single throttle body.
The NGK has a 1.0mm gap, the Ford 1.3mm. Your image seems to support that.
One thing, cracked cam cover gaskets are not that unusual! It's possible yours was cracked, allowing the oil to get to the plug wells, and it was replaced. They're not that expensive but they don't seem to last long without small stress cracks.
I was told that it's better to just repair the crack, they then often go on for a long time. When mine cracked at about 2 years old, I cleaned it all up and put some epoxy over the crack. It's now been fine for a further 3 years. Make of that what you will, but keep an eye on it.
Apparently it is less expensive than the Ford plug and has no real downsides. Some say they have used it instead of the Ford plug and their car would stall immediately after starting but that's most likely been down to other things, its hardly uncommon, especially with the standard single throttle body.
The NGK has a 1.0mm gap, the Ford 1.3mm. Your image seems to support that.
One thing, cracked cam cover gaskets are not that unusual! It's possible yours was cracked, allowing the oil to get to the plug wells, and it was replaced. They're not that expensive but they don't seem to last long without small stress cracks.
I was told that it's better to just repair the crack, they then often go on for a long time. When mine cracked at about 2 years old, I cleaned it all up and put some epoxy over the crack. It's now been fine for a further 3 years. Make of that what you will, but keep an eye on it.
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