SJ410 - Cat or no Cat?

[r s hocking]

Hi all,

Help, I have recently purchased as 1988 SJ410, all fine until the CAT fell to pieces insdie its box. The sytem has been replaced but ever since the car starts fine but runs progessively rougher until it coughs, backfires and splutters to a stop. Having looked under the vehicle all seems well - except there is no CAT on the new exhaust. The vehicle is carbed, not efi so no engine management system, and everything has been cleaned and checked out, so is it possible the CAT, or lack of it is causing the problems?

Any help much appreciated as I am tearing out what little hair I have left.


thanks lots

Sven

[ScottieJ]

Carbed vehicles don't have CATs, it would have never had one fitted from the factory.

I would try some new points and a new condesner in the distributor. when condensers start to break down they have similare symptons and usually kill the points at the same time. you'll need some feeler gauges to set up the points.

[r s hocking]

Hi Scottie,

thanks for coming back

Fitted new points, condenser, dist cap, rotor arm and all work - or I assume so as vehicle starts up and runs fine on the drive - and sometimes on the road before exhibiting the problem as described.

Re the Cat, the original exhaust system had two pipes exiting the manifold which entered a cylindrical box, which according to the manual is the CAT, then exits said box via a single pipe which meets the back silencer box and then out to the tail pipe. Am I reading this completely wrong and if so what is the first cylindrical box for?

really appreciate your time

regards

Sven

[timwilks13]

Pretty sure it's just 2 silencers, but def no cat. Have you got a screenshot of the manual that says it's a CAT?

[ScottieJ]

Trust me it’s 100% not a CAT, as Tim said it’s just a silencer.

Have you tried a new ignition coil, they can get hot and break down after a short journey sometimes.

Where are you and what’s the weather conditions like there? 410s do suffer from carb icing in cold or high humidity weather so they need a hot air feed from the heat shield on the exhaust manifold to the air box

[marve114]

My 410 didn’t have a cat fitted nor does it have one fitted now as I replaced the exhaust

[Anton]

A catalytic converter being removed cannot cause the type of problems you're describing anyway. All they do is get hot, and catalyse the natural breakdown of carbon monoxide into CO2. CO always breaks down into CO2, a catalytic converter just speeds the process up, and causes a small restriction to exhaust flow.

So even if you've had a cat delete, the only symptom of that would be slightly worse emissions on your MOT, and slightly more power. The lack of a cat cannot cause the problems you're describing. Have you had a look at the ignition coil? Scottie's suggestion makes sense. Also, what carb do you have fitted? I'm told the standard 410 carb is pretty good, but the problems you describe *could* be caused by a faulty auto-choke. Maybe. Or maybe your air-fuel ratio is set waaay too lean, and the auto-choke is the only thing keeping you running - when it disengages because the engine heats up, the air/fuel mix becomes too lean and the car dies. Again, just a maybe on that one. I'm thinking ScottieJ probably has the right answer on this one.