To confirm, the part number for the rochester (pressure control valve) on the single canister system is CBC7714

https://www.jaguarclassicparts.com/uk/part/CBC7714

This is no longer available normally, unless you run across some old stock.

As referenced above and elsewhere the alternate now is the ACDelco 214-552 Vapor Pressure Control Valve.

Here's a recent thread here on the subject:

https://www.jaguarforums.com/forum/x...ntinued-81248/

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Well, although I'm not a fan of just throwing parts at the car, with some of these various symptoms I've also experienced, and the fact that I know that my rochester and purge valve are original 22+ years old and 100k miles old... I just went ahead and ordered the ACDelco rochester valve ($25) and Jaguar OEM purge valve ($48) and will replace as preventive maintenance given the relatively low cost.


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I assume you can see it plugged in into the intake? Its just not accessible?
If you can try to follow it, the other end is plugged in next to either brake lines or some transmission lines near the bulkhead behind a metal connector that I've marked red in the attached pic. If you just follow the vacuum line and pull it from above the engine it should come off easily.

Further pic here:

https://www.jaguarforums.com/forum/x...09/#post731770

 

Hi All,

My car is still with the Jaguar specialist. The snow we had a week or so ago in the UK held things up. I arrived just as it begun!

On first inspection the specialist advised me there is an issue with my throttle body and he would have recommended a new one but they are not produced any more. They are doing more tests on my car, so this is the first issue detected...

Does anyone know who reconditions these?

Cheers,
Nick

 

You can clean it yourself as they bind open other then that mechanically there is not much to go wrong . I think he's pulling a Trump on you and selling you some snake oil .

 

Sounds like lies to me too
What problem with the TB is it? As far as its not cracked, I don't even think it can ever go wrong to a point where you'd have to replace it. Sure, the spring might need a replacement if it doesn't close but you can simply add an extra turn on each of the three springs and that will work fine again(actually I'd recommend it). Other than that it might just need cleaning and setting up a 0.02 gap when closed but I thought you already had it cleaned up?
TPS and IACV are separate to the TB and can be tested and replaced separately if needed.

 

When I first bought my first 96, I had Idle issues. I took it to the dealer. They wanted to charge me over $3k to replace the throttle body and the IACV (which tend to break when removing them...according to the dealer, so it was like $2,300 for the throttle body install and another $700 for the IACV)

I took it to my local shop and he cleaned it up for $50. Car was back to normal.

That’s when I first discovered how simple it is to clean these things up. There was no way I needed a new throttle body. For the second car, it was one of the first things I did...it also had the high idle. It is something everyone should do every couple of years.


....unfortunately I am concerned about what else your shop finds.....

 

Hi All,

Thanks for your replies and concerns.

I don't believe the mechanic in question is trying to sell me anything I don't need, it appears to be the opposite. When I dropped off the car he spent time observing how it idles so he could see the oscillating revs at idle and how the engine occasionally misses a beat whilst I was there. As to be expected at that moment the car was behaving itself! Whilst doing so he mentioned the revs in my car do not fall as quickly as he would expect and he mentioned I may have a sticking throttle body. He then went on to say they are not made any more and if it had been cleaned before and the issue remains the butterfly could be warped. He was not offering to sell me a new or used one or recondition the old one.

His plan for the car was to the usual diagnostics and an emissions test and see the results. I spoke to him today and he said the Jaguar diagnostics report no faults on the car (beside historic ones that have been addressed by my previous activities), he is saying on initial inspection there does not seem to be anything wrong with my car... Which at the moment leaves me pretty much where I started...

My throttle body has been cleaned in the past, but I don't know how well. At this point in time my thoughts are buy a second hand eBay throttle body, clean it myself, renew the spring if needed and renew the IACV as recommended previously.

At least if you do it yourself you know it will have been done properly.

Arrgh

Nick

 

That makes more sense. I don't think your problem is TB related, sticky TB would not affect the idle in a way you described. Re the springs, the bottom one can be replaced, they are available from JCP and cost ~90p.

Re the two other springs check this post how to solve it:

https://www.jaguarforums.com/forum/x...0/#post1837396

Make sure to heat up the TB before undoing the IACV bolts, this way you might have a chance of undoing them without snapping them.

 

Oh yes they can! When I got my car it was low mileage (80,000km) but must have been what I call a "Safeway car", i.e. driven 3 blocks to the grocery store and then home again.

The throttle was badly gummed up, so I did all the usual things: took it off and cleaned it, did the spring adjustment etc, and I could still feel how sticky the shaft was when turning it by hand and it didn't want to close properly. It would idle high and on the highway wouldn't slow down when I took my foot off the gas. I replaced the throttle body and all was cured.

Whatever was in there gone into the bushings for the throttle shaft and stuck there, and I couldn't get it out. No parts are available, so replacement was the only course of action.

 

If it didn't close then TPS showed too high voltage hence your high rpm. The only thing I can think off is maybe you fitted the plate itself incorrectly? This can be fitted positioned both ways but it will only work with the X(on the plate) outwards the engine(I think that was the symbol on my throttle plate). If its fitted the wrong way it will not close properly and feels sticky because the plate itself closes fully at a slight angle and is cut at a slight angle too.
Also I actually had to lightly sand my TB to get all the old, what looked like, lime scale on the TB surface, whatever I used to clean it, I couldn't get that top layer of this scale that was visible under running water off. In the end I've sanded it down with 800 grit paper and it then closed and open perfectly.
Re the shaft, I cant remember seeing any seals or bearings there so as far as it wasn't mechanically damaged I cant think of any other reason for it to stick in the way you described

 

The TB was the original, when I got the car it had a full service history and one incident was noted where the owner went off the road because she couldn't stop the car due to the sticking throttle. That was one of the reasons they were selling it, the dealer couldn't fix it 100%.

As I mentioned the car was used for many short trips, so there is lots of crankcase blowby. That vent enters the intake just ahead of the throttle, and the throttle shaft is vertical. All the sticky goo accumulated on the throttle shaft and ran down into the lower bushing for the throttle shaft. When I got the car the throttle plate and body was an awful mess, coated in this black sticky goo. I could close the throttle fully by hand and the revs would drop, but i t wouldn't close under spring pressure. It would close most of the way, but not all the way, all the time. On the road I could get it to close 90% of the time by putting the car in neutral, and blipping the throttle as fast and hard as I could. Then the spring could slam the plate shut. Not Jaguar type behaviour!

I had taken the TB off and cleaned it, but I couldn't get everything out from the throttle shaft, it would still stick on the last 5% of it's travel to closed. Always would close by hand, but was gummy. I replaced the TB and all the problems went away.

 

Just thought I'd update this as my own misfire problems came with a vengeance and not sure whether the same thing was mentioned in this topic, maybe its somehow related. Since my misfire only happened when running on petrol(fine on LPG) I knew it was fuel related. Car was generally running fine when above 1200RPM but below that would often stall or misfire.
Got a fuel pressure gauge and an adapter, connected everything up while it was misfiring and it showed fuel pressure just above 20PSI, clearly too little. Plugged in return line and fuel pressure went up to 50PSI which suggest a dead fuel pressure regulator?
Might be worth checking this Nick, if yours is still running bad.

 

Definitely a bad regulator. I'd change the fuel filter too, just on general principals.

 

A clogged fuel filter will eventually show full fuel pressure after a while if you have the output capped . Just won't deliver pressure / volume amount . With the return open to the tank there is the possibility that with the injectors spitting the regulator never got enough fuel pressure left over to get your 43 PSI . Both items don't last forever , when was the last time the filter was changed ?

 

Hi Katar83,

Thanks for your comments about fuel pressure as a possible cause. I have not advertised the fact as LPG often gets blamed for any issue on a car when the (perhaps uninformed) learn you have it installed, but my car also has LPG fitted. This my second Jag on LPG and my 3rd LPG converted car (the other is on my Subaru - 70K on LPG). My idle issues appear on both petrol and LPG (slightly worse on LPG). Currently my throttle body is being reconditioned and I will be fitting it along with a new IACV and TPS. Hopefully that will fix this once and for all.

Otherwise it's Autotrader - only joking.

Cheers and sorry for the delay in replying.

Nick

 

Any luck Nick?

LPG is actually very helpful in these scenarios because

a) its less tolerable to ignition faults and it shows these way quicker than when running on petrol, eg a failing coil will happily work fine on petrol, but will cause backfires on LPG and that's something that you tend to notice straight away
b) you can instantly say whether the fault is with ignition or fuelling

In your case we know straight away that since its running the same on petrol and LPG, its most likely either ignition related or an air leak.
Another advantage of LPG setup is that it comes with a much better monitoring system and diagnostics!
What LPG type you're running? Multipoint or mixer ring? Even the latter normally comes with an interface that should give you a lot of very useful info. If its multipoint then you should have full diagnostics down to a single cylinder.

I only got my fuel pressure regulator replaced recently, been driving on LPG only for a while and got to fuel filter too. It was indeed completely clogged, no free flowing fuel from the output at all, wouldn't surprise me if it was 20 years old. Of course it didn't want to come out without a fight. Took half a day to replace.

 

Hello Katar83,

I'm a big fan of LPG, this is the third car I have had with it installed. I have a EMER (AEB-based) multi point injection system installed. Interesting point you make about using the diagnostic interface of the LPG system, I have no idea how to access that, but still interesting.

My car drives on both petrol and LPG with similar symptoms however on LPG it is just that little worse, just a little. Currently it has the oscillating revs at idle when heated up, which can on occasions go so low that the car nearly stalls. It also has flat spots which is exactly the same regardless of fuel, it is as if the throtte is not moving and then all of a sudden does.

As you may recall I sent a second hand throttle body off to Maxbore in America to be reconditioned, but not overly bored (due to people finding the car too snappy on the throttle with a heavily bored out TB). I now have the throttle body back and soon will have this fitted along with a new Idle Air Control Valve and new Throttle Position sensor.

Interestingly my friend, who lives near me and has two Jags (one of them also an XJR X300) found a classic Jag specialist near to us who specialise in eType restorations but will do later Jags if they are interesting. They did some good work on his XJS and I am going to ask them to fit the new items, which will save me an inconvenient trip to my usual specialist in London.

Thanks,
Nick

 

I haven't worked on LPG systems in nearly 20 years, but in those days they used to "piggy-back" off the injection signals from the gasoline EMS. Unless modern LPG systems have their own oxygen sensors, in a modified exhaust system, then they must at least be using the OE oxygerns sensors themselves. However, if modern systems still "piggy-back" off the gasoline EMS, then the driveability on LPG could be affected by signals provided to the gasoline EMS; - oxygen sensor signals, AFM signal, coolant temp signal, crank sensor signal.


Unless the LPG EMS system is completely independent of the OE system, I don't think it possible to be certain that the problem is ignition related.

 

LPG system will use all the car sensors, it just gives you a much better interface for everything, plus completely separate to petrol fueling maps down to each independent LPG injector. You can set it up to run without a MAF, or o2 ot CTS sensor, kinda gives you a much better chance of figuring out what and where is wrong as you can freely change the fuelling map as needed and see what happens.


To get to interface, look for a diagnostic plug under bonnet, it must be somewhere there, then get an adapter for a PC, software can be downloaded of the internet.
Let us know how you get on with the new TB and TPS, hope it all works well.