Hi

Have what might / might not be 2 separate issues on my 136000 mile x300.

Idles ok (ish) from cold but when warm, starts to hunt a little - if you blip the pedal, is settles down for a moment but then starts hunting again. Have had a look at the coil packs but can't see anything obvious such as any charring or burning.

Car drives fine - can sometimes feel a little sluggish at pull-away for a few seconds but then picks up fine. However for some reason around 65-75 MPH and 2500 revs (or around that), there is a real flat spot /misfire which lasts for a second or two and then car will pick up fine to 80 - 90 MPH and cruise at that speed no problem.

I'm guessing that these are 2 separate issues but am not entirely sure where to start - have a cheap code reader which showed a code P1138 which I cleared and 100 miles later, hasn't returned.

Many thanks

Mike

 

Mike,

A couple of things come into my brain, fun begins.

Remove the intake bellows, right at the throttle body, take a solvent soaked rag (petrol will do) and wipe out the black goo that is in there. It reeks havoc with idle.

That same black goo (oil based) has also run down the throttle shaft, thanks to gravity, and entered the TPS (throttle position sensor), which is mounted under the throttle body. Access is near on impossible with the oil filter attached. Remove that TPS, purchase some "contact cleaner" in p/pack can, spray it thru the shaft opening, so it flows inside the TPS, and keep at it until it seems clean. Some drill a TINY hole in the base of the TPS to allow this solvent to exit, choice belong you, I did not. This is fiddly, and time consuming, but fixes 98% of them.

Fuel filter getting past its use by date is also springing to mind, but not high on the list. However 5 years is long enough for any fuel filter.

I would then go around the various plugs in the engine bay and simply unplug and replug them. Things like the MAF, CTS (coolant temp sensor), CAS (crank angle sensor), Cam sensor, and the TPS. Sometimes just old age crud in these plugs reeks havoc.

If i think of any more I will return.

 

Grant

Thanks for this - I'm hoping to grab a day off work this week so I can start giving this issue some serious attention.

Have been driving the car for most of today and seems to have got more sluggish as the day has gone on.

The joys of old Jaguars - have just finally got my 86 xj6 running again after being laid up for months with various problems and now have to start on this one! Hey ho....

Cheers

Mike

 

Mike,

I agree.

I just uncovered the '63 MK10 to use as the shopping car, again, sooooooo sick of dings and dents in the X300 and the XJ-S.

Have not started it for 12 months, some fresh "go juice", pumps ticking merrily in the boot, 3 rotations and life begins. Top off the trans and engine oil (they leak), a splash of water in the radiator, and shopping centre car parks, BE VERY AFRAID, I am on my way. Best part of the MK10, is, it is waaaaay too big for their allocated spaces, so I just abandon it wherever I like, and no one has ever challenged me. The body is REAL steel, so shopping trolleys fail in their attempt to do harm, as do newer cars, then add to that the look of a MK10, really, who wants to park near that??.

I reckon your TPS is infected with oil, and should come sweet with a good clean out, fingers crossed.

 

Hi Grant

Having read through a lot of the misfire posts on here, everything seems to point towards the TPS - forgot to mention that gear-changes can on occassion be accompanied with a jolt / jerk - not sure if this is something separate or another symptom of the TPS.

Need to check something - If I remove the TPS and clean it, do I need to then take the car to a dealer to have the system recalibrated? I've seen various posts on here about high idle etc when the TPS is replaced but can't quite fathom out whether this applies for just removing / cleaning?

Just to add to my woes, the alternator belt on my Series 3 sheared off on the way to the office today - the fun never ends. At least I've still got my ancient MX-5 to fall back on!!

Thanks again

Mike

 

On the 3.2 the TPS has nothing to do with gear change points, it is a mechanical transmission with a throttle control cable for that purpose. The cable may be set too tight, but my first point is the trans fluid. I use Synthetic Multi Vehicle ATF in all the Jags, and significantly smoother, especially the X300.

The TPS is basically "not adjustable", although there is some very minute slack in the screw holes, BUT, as long as you DO NOT turn the ign ON the ECU will have NO IDEA that you have removed that unit and replugged it again.

When I did mine I simply sat it back up and tightened the screws, and that was it. The only extra thing I did was to replace those 2 mounting screws with 2 that have a 6mm hex head, so removal next time HAHA, should be simpler than dropping the oil filter. Add to that the fact that I always change the oil filter from the TOP, so that bellows comes off regularly, and that oily muck (very little now) is wiped out each and every oil change.

I think the recal is mainly 4ltr related.

 

Grant,

Thanks for the replies - it is much appreciated - the X300 is a bit of an unknown for me having spent most of my time working on the Series 3 so I'm having to make myself quickly familiar with this model. I think I've possibly been confusing myself by looking at posts / fixes for the 4.0 car which obviously isn't the same thing!!

Am slowly working my way through the various niggles on this car - when I got it, the A/c wasn't working and the PAS was very heavy. A new PAS pump and an A/c recharge have sorted those problems (although the A/c also needed a bit of electrical jiggery pokery before a dodgy relay was identified).

Am just left with the misfire and jerky gear-change the latter has started to really get me thinking - the fluid level is ok and looks clean with no burnt smell about it - will have a look at the cable accordingly - hopefully this isn't the start of anything serious with the transmission - have had two xj8's, both of which needed replacement gearboxes well before 80,000 miles although from what I understand, the boxes on those were a real weak point (along with Nikasil liners and timing chain tensioners).

Oops - forgot the occassional timing chain rattle on start-up as well - doesn't happen every time - tensioners to add to the list! Have you ever replaced yours? How difficult a job is it? The secondary one doesn't look like an enormous job but I would guess it makes sense to do them all at once....

Once again, many thanks.

Cheers

Mike

 

Grant

Thanks for the advice on the cables - both the throttle / gear-shift cables were very slack - have tightened both and the drive is much improved - have still got to tweak the gear-shift cable a bit as the change between 3rd / 4th is a little jerky (rather than 1st - 2nd which is now smooth!).

Throttle body off next - looks like a lot of gunk / oil etc built up around the whole unit - hopefully this will improve the rough idle and misfire.

Many thanks again - you're a star mate.

Mike