Sluggish V8 and possibly blocked cats

[PeterTh]

Hello,
As there is more experiance of V8 engines in the US compared to my end of the world I hope some one can give me some advice.My 1999 D II V8 auto has started to give me headache. The other day it suddenly started to be very slow. I mean can´t go above 60 km/h slow. Checking the fault codes I had a P1300 (catalytical damaging level of misfire) code which I cleared and it hasn´t come back. Today when testing I got a P303 code so I definately have some misfire going on. At the same time as these problems started I got a quite substantial rattle from one or both catalysts. I strongly suspect a blocked cat to be the cause of the lack of power. I have access to another downpipe with cats from a donor vehicle so I will try that but my concern really is if blocked cats could cause these misfires and codes? Engine revs ok when stationary and there is no Check Engine Light. Also the Engine temp is normal and the car does not use any coolant.

Is there anything I could check using a Nanocom? I have looked at the MAF readings and it looks like it is increasing together with the revs but i don´t really know what would be normal values. Also the Nanocom does not show any misfiring cylinders.

Thanks,
Peter

 

[Tugela]

Peter, I had a failing catalytic converter cause error codes on my Disco 1 recently, (P1305, if I remember correctly). I replaced it and the code has not returned, everything is running great. However I did also have to replace one oxygen sensor which failed shortly thereafter. I still have a slight rattling sound, as I think part of the catalytic element broke off, got blown downstream, and lodged in my muffler or resonator. If your cats are rattling it's a good idea to replace them anyway.

If you have access to a replacement Y-pipe for free then that's a good place to start. Don't forget new gaskets (and seal it up good with some ABBA fish paste! Skol!).

 

[PeterTh]

Even though I didn´t have any ABBA fishpaste handy the change to another used downpipe cured my problem. One of the old catalysts had a big chunk of material loose in it effectively blocking it.

//Peter :victory: