Erratic engine

[Robbie123]

Whilst driving the car i noticed that it started to loose power occasionally just for a second, this happened on a few occasions but did not stay long enough to diagnose a fault. Then last time out it developed, i was only doing what would be a 10 mile round trip and on the way to my destination i started to experience loss of power when i tried to accelerate. On the way back the problem got worse, when i was going at a set speed it seemed ok but if i need to accelerate it tried to stall and then it would surge forward, very erratic, getting up to speed was a real problem, it stalled at 2 junctions. Anyway i got home ok but now wondering what the likely fault could be. To assist my car is a 2001 XKR. 2 weeks ago i started to get an amber warning saying trac and acc not working and spoke to my mechanic who advised he would get the car in shortly to diagnose, don't know whether this could be related? Any thoughts

[Astromorg]

I would start with the fuel system. What is the mileage of the car and when was the fuel filter last changed? Do you have any facility to check the fuel pressure either at the schrader valve on the fuel line in the engine bay or, preferably, using a plug-in scanner that will let you see the pressure while the fault occurs.

It could be a fuel pump giving up, maybe too briefly to trigger a MIL . Although the XKRs have two pumps, it's not unheard of for the first one to fail and go unnoticed until its partner follows!

It could also be a coil/spark plug problem, but without a MIL and fault code, confirming that and identifying the offending cylinder is more difficult.

I always carry one of these devices ready to plug into the diagnostic socket and communicate with the Torque Pro app my Android phone by Bluetooth. (There are cheaper versions but they have a wide reputation for unreliability). (iPhones, as ever, require a more specific scanner and app)

https://www.ebay.co.uk/itm/OBD2-II-ELM3 ... SwGAVe4E2p

I can then read a useful range of engine values, including instantaneous fuel pressure, air flow, true engine temperature and more. Ideal for a quick evaluation of a problem that occurs while out and about. The Viecar is about £15 -20 and the Torque Pro app about a fiver for the full version.

[Robbie123]

The mileage on the car is 115000, will check about the fuel filter. To assist i have just started the car and it started as normal and revs lovely, this is a fault that starts and get worse the warmer the engine gets, does a fuel pump react in this way or would the problem be there at start up? Regarding the further information given, are you saying if i buy the Viecar and torque pro app this could give me enough information to provide to you which could help to diagnose the problem?

[Astromorg]

Wow! There's a leading question!

If you're not too sure of getting general use out of Viecar, I don't think I'd recommend you get one just for this situation.
What I was saying was that with that scanner you'd be able to determine whether the fuel pressure is a contributing factor by watching the pressure reading to see if it fluctuates in time with the erratic engine performance. If it doesn't, then without a specific fault code, it could get difficult trying to solve it with only the Torque App which is not much more than an emergency aid.

On the basis that there are no codes I would still start with the fuel filter as a simple low cost way ahead that will not be money wasted even if it turns out not to be the direct cause of the misfire.

Is it too much to hope that you're in the Hampshire South coast area where I'm based and could maybe help in person?

[Robbie123]

Thank you again for your reply, unlucky for me I am in the midlands so out of you area. Sounds like the diagnostic equipment may be needed so will get it to one of my 2 local garages who have both done work for me in the past and both are reasonable price wise. Will let you know the result.

[Robbie123]

Found the problem, gearbox needed oil change and new filter, not engine after all, now running very sweet