[QLD] Catalytic Converter Problems [Lexus LS400]

[Zarconia]

Evening Gentlemen and possibly Gentlewomen

Having an odd problem with an LS400 I recently purchased and just chasing some ideas on what it could be.

Problems include:

- After running for 5-10 minutes both of the cats glow red hot
- For a few seconds on startup seems to backfire through the intake once throttle is applied, however disappears once the cats begin to glow
- Rich smell of unburnt fuel and white smoke stemming from the cats after a while (Seems to have disappeared after running a few times)

Now I've got theories and just trying to see if I've missed any?

-Timing may be out. (Purchased with chewed timing belt, water pump and idler bearing, Replaced with brand new items and aligned to the timing marks on the case)
-Cats are clogged. (I've tried removing both oxy sensors with the problem still occurring, however both sensors are on the outlet side of the cats so I really don't see it helping anything)

Appreciate any help guys

 

[wraith]

Sounds like blocked cats to me.

 

[delcowizzid]

what year is it and was the belt completely snapped

 

[wraith]

Fail. Didn't read the post right. Could be timing related as well. Seems more likely then 2 cats blocked.

 

[ari666]

reckon youre a tooth out on the belt. recheck your marks.

 

[Zarconia]

It's a 92 and yeah pretty much ate it for breakfast, decent job of it.

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Completely seized the water pump as well.

I've re-done the timing a few times now according to the cranks timing marks and has me stumped if or how it's skipping teeth but it does seem likely.

 

[Brett_jjj]

If the timing belt snapped and the valves have just "kissed" the tops of the pistons, it may have leaking valves if its bent or marked the valve seat surfaces in any way. Theres a big chance its done some internal damage though..

 

[wraith]

If the timing belt snapped and the valves have just "kissed" the tops of the pistons, it may have leaking valves if its bent or marked the valve seat surfaces in any way. Theres a big chance its done some internal damage though..

Only the VVTI is interference style. Older ones aren't.

 

[Ian Johnston]

Wraith is correct in his statement.

 

[ari666]

does it have variable timing on the exhaust cam? the type that needs the preload on it before installing? or are they just set straight gears?