Hi all,

I recently inherited a 1997 coupe from my late father. He didn’t use it much for the last few years of his life but I’m currently getting it all back to tip top condition.

On starting it for the first time though, idle was quite rough, almost as if it’s trying to stop itself stalling. Dash showed orange light and message saying engine fault and poor vehicle performance. There was no check engine light though and my mechanic read the system and it says no fault codes.

He replaced all spark plugs for me, he said two of the coils were slightly oily but seem to be working ok as they would throw a code if not. He said jags don’t like sitting for a while and to drive it and see if anything changes.

Nothing has over the last week. The car starts fine from cold but when warm it will stall as soon as the engine cranks unless I give it a little throttle for the first few seconds. Idle still is a little lumpy.

Once moving the car drives great, plenty of power, no issues at all apart from the message which stays on the whole time. Under heavy load though when I really push it, the car seems to cut the power briefly, almost a limp mode but goes back to working fine if I just ease off of a bit.

Looking through the forums for similar issues, people say it’s the ECU with leaking capacitors. I’ve opened mine to check and everything is fine inside, all caps look fine, no leakage, looks perfect.

I’ve charged the battery too with a ctek for 3 days, charge levels are fine, no issues with battery at all.

Does anyone know what this could possibly be please? My mechanic has said to bring it back but he’s not a jag specialist and will likely replace the coils that had oil on them or start replacing things being unfamiliar with common issues. Thanks for any advice.

 

I know you've charged the battery but how old is it and what is voltage at the terminals? If the battery is 5 years old or older (should be a date code on it) - replace it and go from there

 

Sounds like there were (maybe still are) codes (DTCs) - well worth reading them.

At a guess, at least failing coils, but codes really help.

 

Old gas???
Clogged fuel filter?
How long did it sit?

Try completely disconnecting the MAF sensor and see if that produces a change in how it's running. Its in the RH front corner of engine bay on top of the 3-4 inch tube from the air filter housing. Google "Jaguar XK8 MAF sensor location" and you'll find it.

Also, if you don't have one, get an inexpensive (25$) Torque Pro OBD reader on Amazon, plug it in and set it up. Check for codes.

Go thru the functions of the OBD and create a "guage" on your phone in the Torque Pro app for STFT, LTFT A&B banks. Another "guage" for MAF which will give a grams/second reading for air into the engine/intakes (with MAF reconnected of course). Car warm and in P or N it should read more than 5.3 g/s. Around 6 or so in R or D.

Spend 20bucks and get a replacement coolant temp sensor (CTS)... Inspect the plug/connector to the CTS. And careful, CTSs are all not alike. Denso or Bosch are good, then Hella, find a quality brand name. Post a photo of what you PLAN to buy as we have discovered that the sellers are confusing oil temp sensors, and stuff, with the right Jaguar XK's CTSs. It's a PITA to learn late that you have the wrong one.

Dig around and clean up ground and power connections,,, ANY you come across especially in the engine bay. There are 12v/B+ connections (13mm bolts) at every fuse box - remove bolt (carefully), clean with steel wool, replace. UnSeat and reseat all kinds of fuses. The little ones, especially in the boxes in the engine bay. 3 boxes I think. 2 on LH one on RH side under the plastic covers. You'll see them.

You'll get the car right. No doubt.

Also, have a look at the air filter. Inspect tube from air filter to throttle body/like the old carburetor for splits and cracks.

 

Not used much for 3 years ...new battery ..About £56 on e bay delivered next day..then with it running at 2000rpm check the battery voltage to see if the alternator is charging ..expect 14v +

 

Wow, Man... What kind of battery can y'all get for £56 over there... Here, they are like 120+$...!

 

they all seem to be made in Korea these days ..Hanhookk sealed Calcium . What you are buying is a lump of lead..they come down the line and some get a 1 year warrantee sticker and some a 4 year ..no difference

 

Thanks for all the help all. I tried all of the above, turned out when my plugs were changed my mechanic forgot to plug the maf back in! Plugged it back in, put in some bk44 fuel cleaner, topped up with fresh petrol, running like an absolute dream!

Thanks again for all the help.

One thing I did come across when reading too was to ensure the throttle cable had not stretched over the years. I couldn’t make head nor tail of the description how to check, but if someone could advise from the attached picture alone I’d be really grateful! Thanks again all

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Shweeet!