Coming back from a highway trip the engine went to idle. Had it towed home and this morning started checking things. Fuel pressure is 30 to 40 lbs. Engine cold it runs normal, smooth idle, good throttle response and revs up ok.
As the engine warms up the idle gets rougher, until it barely runs and has no throttle response.
Codes show P1000, P1646, P0300 and P1316. P 1646 is no relay#2, which is ok since I have a standard 2000 xk8. P0300 is explainable because of the rough idle. P1316 says MAP, TP, ECT, IAT or ECM. Graphing shows TP is normal and shows position, cleaned the MAF, doubt its the ECM since its a temperature problem. So that leaves the ECT or IAT.


At this point I am looking for suggestions from someone who may have had this problem and resolved it.

 

P1646 is a bad O2 sensor or sensor circuit for sensor 2/1. P1316 is a misfire and is related to P0300, probalby a bad coil or injector. Be careful getting code explanations anywhere but Alldata or similar speciality providers.

 

I was trying to relate the codes to hot running only problems . It is possible that a coil has a bad winding and it only shorts when the shellac coated coil wiring gets hot and expands, shorting out. I have had this happen on magnetos before. I would get the coils tested or get a new one and switch them out one by one. The hot-only misfire is probably not related to the O2 sensor problem. Even so... I would fix the sensor first and see if it fixes things.

 

I have a bad circuit on the upstream ox sensor but its been there awhile, its only a trim device, and has no effect once the sensor is hot. The misfire is on all cylinders, and car will not respond to throttle and shows "failsafe" Any other ideas?


Thanks so far

 

Both of these sensor can be monitored over OBDII to see if the readings make sense when the engine is hot.

 

The codes don't indicate misfires on all cylinders, how do you know this? In my experience, an engine misfiring on all cylinders is an engine not running. Teh upstream O2sensor is a primary mixture control device. If it is bad, you will get a wrong mixture on that bank. The ECU has a map that will run to keep the engine running in open loop if the sensor is bad.

 

Yesterday I found the intake hose/bellows had breaks in thhe bottom of the bellows. Patched it until a new one arrives, cleaned the Mass airflow meter again, replaced the leaky valve covers gaskets and cleaned up some loose wires connectors and guess what, its running fine this morning.

My training as a Jag tech goes back to the 80's and 90's so I fine this forum helpful on the newer models. The course I took on Fuel injection related the parts that have a major effect on fueling, and those devices that trim the fuel for emission. The ox sensor is one of those trim devices, and the heaters only work until the exhaust gets hot. The IT sensor is another trim device. The Air flow meter, throttle body and water temp have a major effect. That,s why only a yellow warning light comes on, warning of an emission failure.

Appreciate all the input, I may be back to revisit this later if the fault returns.

 

The driver side valve cover has a small breather hose going to it with a special connection.

Remove this hose, unclog it,so the driver side breather hose is not taking all the oil vapor in, and throwing it on your maf, which will make it mad as the elements heat up.

Also hope you changed or cleaned the Baffle Filters in the valve covers and cleaned the throttle body.

This a a known TSB for our cars at Jaguar.

 

Did not know about the valve cover, I have only done the right side because it was the one leaking, but will be doing the other side later this week so I will clean the baffle. The throttle body looks very clean, the throat is clean and the butterfly, I did give it a shot of the cleaner just for old times sake.

The hose on the bellows is open and very little oil in the old bellows. I did clean it out but will go back and check the hose to the manifold, I assume you mean the hose that has a T, with a branch to each side.

I was using Torque on my Blackberry to read OBD codes and look at the OX sensors, one is flat lined. I have a replacement and will do that this weekend, also purchased an Autel AL519 so now I can see the MAF real time, as well as the ox sensors. It does have a select vehicle option for Jaguar but I think its still a generic code reader and not very specific to Jaguar.

A side note, for those of you that have LED's missing on the third brake light, I found exact replacement bulbs from China and bought enough to replace them all for under $ 3.00 including shipping.

Thanks

 

Problem came back today, as I was leaving the Jag dealership having codes read for abs, they found nothing wrong. Problem comes and goes, runs fine then no throttle response. Changed fuel filter but just a little dirty. Checked fuel pressure and its low, under 30 lbs and drops when the car runs rough to 20lbs, clamping the return line does not bring up the pressure so I guess it back onto the tank and check the pump.