Hi all,

After some advice. My car (EAII) has just had the head replaced as the old one was cracked. Also at the same time, i had the DIFF replaced with one from an ED...

Ever since this work has been carried out the car seems very sluggish and slow. The diff ratio has not changed as the speedo is still accurate, ie when the speedo reads 100, im actually doing 100.. Also my fuel economy has been terrible since. About 350 or 400ks per tank, mostly highway driving...

I spoke with my mechanic earlier today, and he said it sounds as though my CAT could be blocked.

Does this sound reasonable?

It may be possible the cat is blocked.

Was it running OK before the head was replaced (as well as a car with a cracked head could I suppose).

It may be possible the timing was knocked around, or the timing chain may have moved. Maybe have a look at the engine timing and see for starters.

If the cat is blocked, take the car for drive, and after 5 mins on the freeway, the inlet pipe to the cat would be glowing orange. As well as part of your exhaust manifold.

That would be if the cat is completely blocked im guessing? If the flow was just restricted, would this have the same effect?

Also, the car was running pretty much fine before the head was replaced. Just a little hard to start when cold.

The timing seems to be ok, the car runs smoothly.

That would be if the cat is completely blocked im guessing? If the flow was just restricted, would this have the same effect?

Also, the car was running pretty much fine before the head was replaced. Just a little hard to start when cold.

The timing seems to be ok, the car runs smoothly.

check the timing first then change cat. but it might also be o2 sensor or MAP sensor.

That would be even if the cat was partially blocked.

Have you actually checked the timing yourself. A Falcon will idle smoothly with a fair amount of advance or retard on the timing, but once you get moving, then you know about a timing problem.

An example, my old mans NL. Somehow (I'm guessing mechanic didnt tighten bolts properly) the dizzy moved. Timing went to about 30 degrees ATDC. So esentially, the mixture was igniting as it was leaving the exhaust. This caused the exhaust manifold to glow a nice orange, as well have almost 0 performance. But it still idled well and started ok.

So I fixed the timing, and car seemed to be better, but still got the bits before the cat to glow a bit.

So then decided the cat must be blocked. $180 later, car running perfect again.

Cut the old cat open and found that probably 1/3 or more of the first "filter" on the cat was blocked. Must have been caused by unburnt fuel coming out the exhaust, causing those areas to melt. So that 1/3 was enough to make the car run like crap.

its not too much to get under your car and check the cat shine a torch in there from the engine side you'll know if its blocked just by looking.
but its probly not likley if your car was running ok before, but strange things happen.

i had a second hand cat put on and it was ended up bieng partially blocked got worse within a few weeks. symptoms where: fuel ecconomy worse, loss of power / slugishness, would stall sometimes when downshifting gears.

Sorry to dig up an old post, just thought i would let you all know that the car is now fixed... Ive changed mechanics and blacklisted my old one.

New mechanic had the car 2 hours and all was fixed. THe timing chain was dead loose, and the timing was miles out. Also the chain tensioner was fairly worn.

Good of the old mechanic to point this out to me, and also great to see he checked the timing (sarcastic comment)

Anyway, all has been fixed now and the car is running better than it ever has !