96 Disco 1 - running rough and misfires after warming up
 

I have been having some issues with my 96 disco. It starts great, runs really well for a while then bogs down and i cant get it to go over 1200rpms. sounds like its misfiring. backfires when i try to rev it up. I initially thought it was a heat issue. replaced my thermostat with a cooler one, put a new temp sensor and viscous fan clutch in it. didn't help. Then it finally threw a code saying that the cam positioning sensor is out. replaced that, still nothing.

It idles great and will run a little while before this starts happening again and it will even idle well when this starts. I also checked my fuel pressure and replaced the filter. The fuel pressure is good and consistent even when it starts acting up.

I have called a few mechanics and scoured the forums, my thoughts are maybe the crank positioning sensor or catalytic converter causing too much back pressure. I have also read that things like this can be caused by the VSS but symptoms of the VSS don't seem to be this drastic.

I could really use some help. I am running out of money. :)

Thanks in advance.

-Ben

Clogged cats is a possibility but my money's on bent reluctor tab, ckps, or low fuel pressure.

Disconnect VSS and try it. Either drive by GPS speed or stay in the slow lane. VSS that fails wants to start shutting down engine (acting as speed limiter). Won't cost very much to try. Another thing is when it does this, pour cold water on the CKP sensor, but usually, since that is just a coil of wire, it won't run at all. Here's Eric's

Do you have any fault code numbers, if so what are they?

Thanks for the quick info guys.

I had a camshaft positioning censor fault code and i put a new one in and reset the system thinking that this would fix the issue but to no avail.

My fuel pressure is excellent even when the car is acting up.

EricTyrell - would a bent reluctor tab cause intermittent issues? my disco runs perfect for a while and then will misfire and bogs down to about 1200 rpms randomly. then if I let it sit a while it will run normally again but will eventually act up no matter what the driving conditions.

also would the CKPS or the VSS cause this type of problem intermittently and at random times?

thanks again

Ben

One more question - is it possible this could be a timing problem?

A friend of mine suggested this but to me it seems as though it would be a constant problem not an intermittent one. any thoughts?

Thanks,

Ben

VSS or CKP can be intermit, but without CKP it won't run.

I had this happen recently while the car was just in park and idling without driving it at all. Would this rule out the VSS?

Yes. You can pour cold water on CKP to see if it makes any difference when this happens.

Update:
Tested the CKP nothing happened. Took it to the muffler shop and had them test my Cats. They said they were clogged so I had new ones put on, 15 minutes after i left the shop had the same problem. I have an appointment on Monday to take it too a specialty Land Rover mechanic to diagnose it. I am Stumped, broke and at my wits end. FYI it is way cheaper to have after market Cats put on that are supposedly of better quality according to the muffler guy, more flow i guess, instead of buying the $500 OEM Y-pipe.

I will post my solution when i get it figured out. Thanks to all who tried to help it was much appreciated.

-Ben