Timing problem, need help.

[GaryVM100]

Have had the car for years with no problems, 32 thousand miles and doing normal maintenance myself. Only drive it in the Summer. Yesterday, as I started to drive away the car made a loud rattle noise like I hit something and slowed like there was something holding it. At first I thought something fell off and I was dragging it, or the brakes or transmission locked up. Now I think it was the engine briefly firing the plugs at the wrong time. It only lasted a few seconds. There were no warning lights and today no codes showed up. Could this be the CAS or the coils? It has new plugs.
I need help!, I'm no mechanic and no one in Connecticut that knows this car or the engine.

[Simon_P]

Welcome!

I remember reading something similar on here a few years ago ago and I think it turned out to be the cat. breaking up. Maybe someone who has experienced this can compare the symptoms.

[Brit-Car-Nut]

Simon, that is a good call. It could also be the Pre-Cat, the owner should have them BOTH checked. When they remove the regular Cat, they can remove the front pipe and "look" at the honeycomb to make sure it isn't burned through. It is just 3 more nuts and the gasket between is steel so reusable.

Late model MGBs had a horrible habit of melting the small, in-line cat and it was like someone smothered the intake... There was nowhere for the exhaust to go.

I have an M100 Pre-Cat that I "inherited" from someone in the US and it had self destructed (melted) and plugged up the engine's ability to breath.

At least, the Cats and Pre-Cats are still available, although fairly expensive. I have a couple USED Pre-Cats but only one NEW Cat left.

[GaryVM100]

Thanks for the advice. I had not thought of the catalytic clogging up. I removed the cat converters on my TVR and the performance improved. I'm going to replace the M100 ignition coils and the plug wires first, to see if that was the problem. Then I'll remove the front cat and see how it looks inside. I don't think the car needs the front cat, so maybe I'll just by pass it in the future.

[GaryVM100]

Can we just gut the insides out of the precat and reinstall it...since it makes little difference to how the car runs.

[HJ2]

Yes you can, and you gain a few horsies on the way!
However, when it is allready off i would reccommend replacing it with a custom downpipe, like the piper one
In all of the above options you will most likely experience boost creep, so save some pennies to get the turbo wastegate ported...
Emptying the pre-cat will give you more exhaust noise as well so be prepared for that.