Good Morning to all.
First time poster on this forum.

I own a 97 3.2 sport with a slightly annoying problem. When driving said vehicle it sometimes has a fault when keeping speed. Ie holding speed at 50. or 60 etc.

The engine loses power and revs drop by 500rpm. then all power comes back and car picks up. then will repeat.
Sometimes turning engine off for a few minutes cures the problem sometimes it just goes away when driving.

Problem is not every time its driven and nor is it constant. But even when it is there engine will idle smoothly albeit slightly high (around 1500) and will also accelerate like a scalded whippet. It's only when trying to hold a constant speed. Also it doesnt matter which gear or speed you are doing.

Thank you for any insights into this problem. Would rather ask on here before it goes into Jaguar dealer for diagnostics.

 

OK, I am going to guess.

Since its a 3.2, you are NOT in the USA.

Using "whippet" has me think the UK???.

Anyway, clean the throttle body internal throat. I use a clean (white) rag, liberally soaked in solvent and wipe it out, keep going until it is clean.

This may not sort all your issues, but will certainly make further diagnosis extremely simple. I think.

Some markets have an EGR (exhaust gas recirculator) system, and that reeks havoc with idle and general running, or so I have read, we dont have that system, luckily.

The CAS (crank angle sensor) and/or its 2 wire connector is another given concern now with simple age, but 100k miles seems to be a common distance failure. Mine went legs up at 163000kms.

The cam angle sensor (that whizzy thing where a distributor once lived) is also creeping up on the failure list, but very slowly.

The fuel filter would also be high on my list, very cheap, not too hard to change, and should be done every 2 years or so.

The list will grow once we know where you are, and others come up with ideas.

 

My apologises. I should have stated that I am in the uk. South Surrey to be exact.
The jag is a full uk spec model and completely factory standard.
Vehicle was garage service up until 137,000 miles. then self serviced after that. I brought it about 3 months ago on 147,000. Went though mot with extremely low emmisions.
Has always started first turn of the key apart from twice when it only cranked over. Sounding like the cam chain had gone. But after 30-40 seconds fired up and ran at 2000rpm on idle. But settled to just over 1k within a about 10 seconds.

 

Good.

I am now leaning toward a grubby throttle body bore.

Since it costs zero, give it a good clean, and see if that sorts anything.

Mine starts at 1100-1200rpm, and settles to 850 in less than 10 seconds, summer or winter.

Vac leaks/unmetered air, comes next, particularly that large bellows on the intake of the throttle body.

At your mileage the crank angle sensor still niggles in my head.

 

I'll have a go at cleaning the throttle body and see what that does. As for the Crank sensor would that be the speed sensor as that is all I can find listed on just jags. If not you have any idea of the part number i should be looking for?
Also forgot to say about the slight soft feel to the front end when on motorways. I think it's the bearings which I will be changing shortly. Plus the bushes on the top of the front dampers as they have hardened and dont meet the mounts anymore lol

 

oooo update. removed the air pipe from throttle body to air box so I could get to the damper nut. And found that the pipework is cacked in oil. the throttle body has oil smears in it and the butterflies are brown. Assuming oil there lol. I'd say that the car is blowing oil up the pressure release pipe.
Is this just a case of using oil flush and changing the oil or is there a trap etc to change aswell?

 

NO.

Oil in that bellows (as i call it) is quite normal, and not just Jags. My sons V6 Commodore S/charged does the same.

I always change my oil filter from the top (lazy bugga I am) and that bellows comes off at every oil change and cleaned out.

Mine also had large oil deposits in it when I first got the car, and after many oil changes using a "good quality" Synthetic oil, and my flush method (see below), it now only has a mist at worst at each change. My oil changes are every 6 months, kms dont count. car now has 200100kms on it, so we have done 60000+ in 3 years, sweet as expected.

My suggestion is that your bellows has possibly NEVER been off, so oil of some quantity in there is normal to me. It will only get to a certain level and then get sucked into the engine.

There is a breather arrangement in the cam cover inside where that hose attaches, and if the cover is ever off, a good clean will do no harm, but the fact there is oil in the bellows means it is allowing breathing to take place, leave sleeping dogs alone.

Engine oil flush, OK, lots of snake oil out there, almost as bad as asking "what oil is best for my car".

I have used for 40+ years a 1/2 litre of "auto trans fluid" in ALL the Jags. Add to the old oil, run at idle in the driveway for about 30 minutes, shut it down, drain the oil at the hottest you can get that plug out without burning yourself. Continue with teh filter change etc as normal.

This has served me well in all the cars, and my kids also do the same with their cars (no Jags at the moment), and no side effects other than a clean engine internally.

The oil used has a marked effect on the breathing, and too heavy an oil, cold temps, short running, etc, all add to the woes.

I run Synthetic 10W/30 in all ours all year round, and never had issues ever. Its summer here now, and we just returned in the X300 from a 2500km cruise at 44+c temps in some places, and the car did exactly what it was designed to do. Ran like a Jaguar.

I would clean all that stuff as best you can, then run it with flush, or whatever you choose, for a time as specified, and then drain that old oil, change the filter, refill with a good quality oil, and see what appears at the next oil change period. This may not fix all your issues, but getting that all cleaned up as it should be, will certainly help when diagnosing the next concern, due to you addressing the "basics".

 

Thanks for that Grant. No idea if the pipe has ever been off before. I only have the service book, no reciepts. So nothing to say whats been done.
I always clean ever part I remove before replacement lol. And have only ever used semi or fully synthetic oils in all my cars. Semi in cheapo things full synth in jags beemers, range rovers etc.
As for the flush I use STP stuff. never use cheap items lol. Not worth the hassle tbh.