Take a look at the temperature sensor, maybe even the wire/pin to the MAF from the sensor in the cross water pipe. Apparently, when it is enriching on startup it performs well, once hot, less so . . .

 

Mmm I thought maybe temp sensor related, I just told my mechanic this morning so I’m awaiting his response…..cheers !

 

My mechanic found throttle cable was not as taught as it should be. When fixed according to procedure she seemed fine. However P0172 &5 back. This was initially fine from the garage but only on a 30 mile run including hot traffic. In fact she was idling a while whilst being diagnosed the second time. After I pulled off, she actually hesitated then cut out! Only just got her started again, seemed like she’d flooded as she was better whilst foot on accelerator . I’m thinking it sounds like over fuelled. But I’m open to suggestions!

 

That’s really starting to sound like a bad tps.

 

Blimey… it’s only done 10,000 miles. They should last 80,000 at least.

 

The first thing that now worries me is I sat there idling in the heat for 20 mins whilst being diagnosed, when I pulled off she didn’t respond well and stalled several times before I just managed to start her with foot slightly on throttle which means to me she’s flooding.
what sensor do you recommend looking at first? Is there a faulty fuel pressure sensor or something maybe? Cheers!

 

You need to use a scanner with live data list and chose all the functions for throttle position. It really sounds like a bad TPS.

 

Thanks addicted2boost.. I’m sure TPS was not the culprit. Can I ask, would taking off the TPS and simply reinstalling it, cause this pain? I had done this to try and recalibrate the faster idle. But maybe I’m thinking I cocked it up? It looks in the right position and idles perfectly, but just a thought?

 

Over fueling is down to a couple of things...
Faulty fuel pressure regulator - you can attach a fuel pressure tool to the fuel rail, it should be around 40psi.
Faulty coolant temp sensor, if this fails a few things can happen, no starts or runs rich because the ECU doesn't know the temp so it defaults to a high fuel rate to keep the engine cool
Faulty Throttle body, although these usually post codes and a warning light, do you have an engine light on the instrument pack?

Above all else an OBD reader and understanding fuel trims will locate the issue in minutes.

 

Sean, thanks… started her up to take to my mechanic this morning. She did have the EML on, but literally 1 min later (and still on cold) EML vanished. I drive her 4 miles (engine got up to temp) and still ok no issue. I’m astonished.
when my mechanic reset the throttle cable on the body according to Jaguar workshop procedure, she seemed fine but then the fault was back. So she sat for a week. Now on start up - I’m guessing some sensor is on its way out or intermittent.

or could it be that she needed 2 drive cycles to “remember” the new throttle position/ cable tightness that was done by mechanic?

cheers ..

 

Still no luck..
there are no faults and until only rich codes when hot.
the TPS doesn’t bring up any codes. I’m reluctant to change that right now as idle is perfect and the part is 10,000 miles.
the scanner says 91deg. C, but how do we know if the actual temp sensor is relaying this info correctly back to the ecu? If it’s busted, then the ecu just thinks she’s still cold, right?
So that would correspond to good performance when cold, but crap when hot?

can someone kindly tell me the exact coolant temp sensor? It can’t be the one for the dash instrument- it must be another one, right?

and could it be the oil temp sensor? Would that affect the fuel performance?

I’m thinking it’s a thicker threaded one but I cannot seem to see where it is or what part.
I’m getting quite worried that I cannot cure such a simple problem!!

 

An OBD tool reporting such as ECT is getting that data from the PCM (one of the many ecus) so you in effect know what the sensor is saying.

For your car I don't know if OBD can read the oil temp (on many cars, yes but may need a proprietary tool).

Bear in mind that if any OBD monitor is not set then many codes cannot flag, so be sure to check that all supported monitors are OK.

 

Ok thanks.. I’m just thinking, when I reconnected the battery and drove off before she’d had time to settle, and was still effectively cold, could it be that I messed up and damaged the TPS?

I would have thought the OBD would have flagged that up though.

cheers

 

TPS will be OK.

You cleared all monitors when you disconnected the battery. Check they all set again or many codes can't flag (& smog fail if relevant).

 

Thanks jagv8. How do I set all monitors again.. not sure what are these monitors exactly?

 

you drive the car. Monitors are things that the OBD system checks like catalyst efficiency, egr flow, fuel tank vapor solenoid opening, etc.

 

Ah ok excuse my ignorance. In other words the sensors re-learn. Yes I did several times and my mechanic.
im awaiting the results from the coolant temp sensor replacement. Will see…

 

The web has full details re OBD monitors ...

 

Resolved- I changed both coolant temp sensor ( not the issue) and the air intake sensor on the TB. I then noticed the plastic clip on the crankcase breather had snapped, making it loose. I’m not sure if it was this or the air intake sensor. But now she seems fine…. Thanks for the advice!!