XJ running badly.

[awg]

Originally Posted by East-Gippsland-XJCherokee

But whats got me stumped is when I changed out the crank sensor it went downhill even further real fast, hence I am going to put the old one back to see what it runs like than. BUt I will do some reading about the 2 oxygen sensors as well, I have ordered lots of replacement parts, and might as well add 2 oxygen sensors to the shopping list, fun never stops hey.

might as well test them with a multimeter as per FSM first?

there are 2 on my 96

I know most fuel probs are electrical, but a dodgy fuel pump/filter could easily give yr symptoms

[Redemptioner]

First culprit will be coil, but based on the fact it gets worse when hot and won't go over 3000 rpm (or there abouts) I would say it is a blocked catalytic converter. If there is no issue a little above idle then it is not likely to be oxygen sensor but that can be checked simply by pulling the plug on the front one (assuming you have not changed the injectors).

Easy way to test is to unplug oxygen sensor and then remove the exhaust pipe after the headers and see if it comes close to good, quick rev will tell you if you can get it to rev past the restriction, it is almost guaranteed to be the CAT if the CAT rattles.

[East-Gippsland-XJCherokee]

First thing I did this morning was to put back the crank position sensor that came off it. And presto, it runs normal and idles perfect sitting in park, revs clean and no sign of anything wrong, now that was what it was like before I change out the CPS, I still had that miss at 3000 and 4000, but at least now the car is driveable.

I took it for a spin with the front O2 sensor disconnected, it still had a slight miss at 3000 and an oh so slight miss at 4000, but it does not buck like it did the day before, so what other words the new CPS is a dud and gladly leave the old one in it. I will have to let the car cool right down to drive it again to see what it does with the front O2 sensor being disconnected, to really give my spin on it if it is the culprit or not. The exhaust tip is also extremely black, indication it is running very rich, and it seems to be going through juice more as well.

The cat has no rumble or makes any sort of noise indicating it is coming apart. I just received a new fuel filter (old one is 12 months old) a new coil is coming this week from Melbourne as it could still be why it has that miss, new plugs (old ones are 12 months old) are on their way, a MAP sensor switch is on its way as well, and a new TPS sensor has been ordered as well. I am about to order a new upstream/pre-cat O2 sensor as my XJ has got over 320,000 k's on it and unless they were changed at one stage they will be truly stuffed or on their way out.

So at this stage, the original problem of that miss is still there, although seems a fair bit less with the upstream O2 sensor disconnected, I am letting the car cool right down, and than reconnect the O2 sensor to see how it acts, than disconnect it again to see if there is a difference. I only have a new fuel filter to put in at this stage, but will start replacing one part at the time as they come in to insure that if it is not the O2 sensor to at least solve this problem and pin point what the problem part was.

My money is still on the O2 sensor as the best milage I get out of a tank of fuel is at very very best 350 k's, and lately (last few weeks) I was under the impression it was using more fuel again.

Thanks so far for all the advice and input, and keep the suggestions coming, and I will update after I drive it late this afternoon after cool down and re-connect the O2 sensor. Stay tuned.

[East-Gippsland-XJCherokee]

Originally Posted by Redemptioner

First culprit will be coil, but based on the fact it gets worse when hot and won't go over 3000 rpm (or there abouts) I would say it is a blocked catalytic converter. If there is no issue a little above idle then it is not likely to be oxygen sensor but that can be checked simply by pulling the plug on the front one (assuming you have not changed the injectors).

Easy way to test is to unplug oxygen sensor and then remove the exhaust pipe after the headers and see if it comes close to good, quick rev will tell you if you can get it to rev past the restriction, it is almost guaranteed to be the CAT if the CAT rattles.

Is there anything you can do with a factory cat? Or it is a throw away item?

[East-Gippsland-XJCherokee]

I forgot to mention, no check engine light came on or error codes via key dance whilst driving with the upstream O2 sensor being disconnected, really thought the ECU would at least warm me some how that it was disconnected.

[awg]

Originally Posted by East-Gippsland-XJCherokee

Is there anything you can do with a factory cat? Or it is a throw away item?

knock the insides clean out if its proven buggered? sure i read somewhere about the strangled cat prob ...maybe search USA forum?

more power too, but obviously not legal for emissions, more experienced advice than mine can be had on that topic hopefully

[East-Gippsland-XJCherokee]

Originally Posted by awg

knock the insides clean out if its proven buggered? sure i read somewhere about the strangled cat prob ...maybe search USA forum?

more power too, but obviously not legal for emissions, more experienced advice than mine can be had on that topic hopefully

Well I am aware of modding a cat, before I retired (early) and move to the country from Melbourne, I was one of them street racers, and most if not all vehicles used to have a hammer and long piece of steel modification done to a cat, if you know what I am getting at?