Throttle adjust / tuning.

So I've read Grant's tuning doc and been having a poke about because I plan to pull the manifolds - I notice that the throttle bodies have stabbings that would potentially allow for setting these up using a vacuum guage - has anyone ever done this ? bit belts and braces I know but we used to do similar on carb setups so I don't see why it couldn't be very effective using a feeler gauge seems a bit hit and miss in a round hole

Just thought's you understand.

 

The 1" balance pipe, and the idle bleed air via the AAV makes it even more hit and miss.

My 85 has NO balance pie, AAV, etc, so the old Carby Balance came out of storage to set the engine where I wanted it.

 

Botheration - forgote about that ridiculous balance and the AAV - it seems quite a juggling act in many of the threads I've now read, the Jaguar workshop manual makes it sound a lot easier - I'm guessing experience trumps manual.

 

Yep, and the Amber Fluid in Brown Bottles.

 

Can't beat that stuff - I've lost years to it ...

 

I'd much rather have a bottle in front of me than a frontal lobotomy

Cheers
DD

 

The AAV is a real PITA, yes.

Years ago, in my XJS days, I had a go a rebuilding the AAV .....which had been stuck for who-knows-how-long. Worked great for a time, then stuck....again. Ignored it after that.

On my present V12 I ditched the AAV entirely and have suffered no ill results, even in cold weather.

As for the throttle set-up, well, it can be a little tricky to get it "just so" but at least you can forget about it for a few years.....unless other work dictates otherwise. The notorious worn-out nylon linkage bushing can frustrate but is easily replaced. But beyond the bushing I've found that wear throughout the entire linkage system can complicate matters.

I like the idea of ditching the balance tube as well. Maybe in the future. The engine has been running like a watch for a long time and I'm perfectly happy to "leave well enough alone" for the time being .

Cheers
DD

 

If the failure modes explained in the workshop manual are anything to go by the typical one is to fail open, the wax or whatever simply stops working so the valve doesn't close, if the adjustment screw is all the way in and doesn't affect idle it is apparently goosed - that's what I read incidentally not my experience. I wan't to pull the manifolds etc off to clean the valley replace as much as possible in there with a view to not going back in for a long time - I'd kind of like to get tthe cam covers redone they don't leak buit they look nasty - but this is entirely a visual thing so I may or may not.

I'm all in favour of the 'not broke don't fix' mentallity - such things usually cascade into mayhem and a trillion unplanned tasks

 

I hear ya !

In some cases it really IS best to do it all at once.

In other cases, being selective is OK. A lot depends on how much labor will be involved if you have to go back over the same ground again.

In the past....other old Jags..... I've spent a ton of money and time replacing things that didn't need replacing.....on the basis of "just because". In recommissioning my present Jag, though, I've experimented with a different approach. A couple examples: There are three u-joints on the sedan driveshaft. I found one to be rough while the other two were smooth. I replaced just the one....and left the other two alone. There was a time when I would've replaced all three "just because". Same with front wheels bearings. Two were worn, two were still perfect. I replaced just the two....when previously I would've replaced all of them.

So far I have no regrets and have saved some money and time. And, as you say, the further you go, the greater the chance of complications and problems.

Cheers
DD

 

I just did the top end half ah refresh and honestly,,, I did more cursing and swearing just now, trying to get the little domed cover back over the end of the rear hub/axle bolt. Guess I need a section of 2inch or something pipe to tap it on square.

If you plan on doing anything with the cam covers have a sandblaster lined up. That was the only thing that delayed my progress. The paint is sufficiently cooked on or it was originally powder coated...It's tough stuff. Would have been a monster job to sand down by hand. I was chasing leaks, still have one (some) but I feel better knowing that the leaks ain't from the cam area and that the leaks are no where as bad as they were. A good cleaning and a repaint of the covers made me feel good. Looks ok, too. Just make sure to cover the holes left by the intakes at all times while working, and have a buddy ready to help you lift them off and put them back on. All in one piece.... Also, choose the intake manifold gaskets, and such... Not a bad job at all. IMHO

Ben, I've been glad to read your posts here! Great voice in the mix! Cheers!

 

Are you suggesting that the manifolds complete with fuel rail etc can be removed in one piece ? hadn't planned that.

For grease caps I have a number of large sockets, used to have a piece of scaffold pole but it has long since vanished.

I believe that the cam covers were once upon a time black, quite how they would have managed to corrode as they have at the back I don't know but I don't like dirt nor corrosion - you never know what it is hiding, once allowed to go unchecked it spreads like Covid, besides I don't like getting covered in black goop that you need a steam cleaner to get off, really frustrated with the weekend so far rain rain rain rain ... did I mention rain ... contented myself with cleaning up the exhaust gas analyser.

This is how I want my covers to look ...

 

yeaaah,,, them are nice! I went red and cooked them I'm my sidewalk oven...





yes, thanks to the advise of folks here that's the route I went. Remove the 24 1/2 inch or 13mm bolts, fuel lines, throttle cables and a couple of other things, and the whole thing comes right off. Leave every thing that adds to the stability of the entire intake assembly like the 1inch cross pipe inplace and it's rigid enough to pick right up and out. I had luck tipping the front end up some to help the rear of the maniflds clear (go under) the two cross braces at the rear of the engine bay...

 

Man, LOVE those red valve covers!

 

Hi Jay

Please could you explain a bit more about how you painted those Covers

What sort of paint did you use and what was the Heat Gun for?

Also if you wouldn't mind sharing, where can I get one of those external Temperature Readers with the probe

Cheers

Alex

 

- I had luck tipping the front end up some to help the rear of the maniflds clear (go under) the two cross braces at the rear of the engine bay...[/QUOTE]

Did you jack up the front of the engine to lift the manifold out?

 

Did you jack up the front of the engine to lift the manifold out?[/QUOTE]

NAH, I reckon he juggled the front of teh manifold assembly "up" slightly, allowing the rear to squeeze out under the 2 cross braces.

EACH TO THEIR OWN.

I remove the 4 bolts and remove those cross braces.
I then take the Injector rail off, leaving the Injectors where they are. You will be fitting new hoses, so simply slice through them all at the midway point.
I then remove the Inlets one at a time, and stuff plugs in the 12 holes looking right at you.

If something fouls, or the juggle goes wrong, and some washer, nut whatever ,that you missed on the "BEFORE I lift anything count" got missed, the engine comes OUT, and gets dismantled to retrieve said item, I am NOT that brave, sorry guys.

I also move EVERY loose item, socket, screwdriver bit, ANYTHING, to the workbench, before lifting either Inlet. All that stuff lost in the "V" by previous fiddlers is a danger item.

 

That last part is right right right! I spent a good time with a magnet and looking and honestly, by the end of that, I was confident that I'd had everything. For fear, I removed all nuts and washers one by one, side at a time, to help with the clarity and confidence that I had everything... But really, it wasn't scary as all that. Just slow and careful.

Engine not moved or jacked but front of car up on jack stands lowest setting - I do this because I have learned that I make MOST of my mistakes when I am fatigued,,, especially when it's because I am in an uncomfortable position for a long time. Bent over the engine bay (I'm like 6.4) get very uncomfortable for me... Then a friend to help lift, and a little jiggling, it came right out. Super pleasing!

Then, I had replaced all hoses and injectors less than 400 to 700 miles ago so I had NO intention on redoing that. So, in my case, to help the top end come out in one piece, it helped that I left everything that connected the two halves in place. The damn thing offers a little, and perfect amount, of flex to be manuvered and removed (and replaced) as a result of the flex...

Still, I had also removed the capstan and all of the wires leaving only the diz cap and oil sensor stand. Also, I had no AC compressor fitted so that gave more room for my viewing pleasure... The area was clean BUT what Grant taught me above (thanks to Grant and others) was at the front of me noggin... No errant bits!!!

The paint oven is petty well documented on YouTube. I used a duplicolor red engine spray paint. The oven is made of cardboard with a inner lining of the shiny side of aluminum foil,,, duct tape on the outside. A small hole at the top of the cardboard box for the heat gun. I got the thermometer at Walmart for like 10bucks. Reasonably accurate if not completely, who knows. Cooked at like 250+ or - for 2 hours 20min after last coat of paint. Super cheap compared to powder coating...

Had the covers sandblasted (a service wasn't easy find believe it or not)... Then washed and rewashed with acetone... Can you believe me, Barney Rubble, even wore gloves for the "skin oils", omg. What's happening to me, lol

But YUP. Was cautious and filled ALL the holes IMMEDIATELY with cotton cloth (not paper towels) right after removing the intakes... AND importantly, left the spark plugs in the ENTIRE time. No want for a mistake there...

Worked out good I think but I still have a lot of cleaning up to do in the engine area... Recently removed all to do with the carbon canister...

 

Looks pretty, I'm redoing all my injectors etc so I guess it isn't such an issue for me to pop them out - that said even they leave a very inviting hole. I plan to print some blanking plugs - just need the hole dimensions. I plan to buy manifolds and cam covers because my number one objective is to get a rolling restore, I don't plan to hold up the rolling part for cosmetics, I can work on manifolds etc over the winter at my leisure. Experience with my previous projects has taught me not to go mental or it will simply become just another pile of parts on the driveway waiting on me to refocus, cosmetics whilst important to me are not going to hinder this recommission.

Besides once fully roadworthy I'm sure numerous additional projects will present themselves.

 

I have a bit or hesitation sometimes when I am idling at a light and go to resume at light change. Its worse before the car gets warmed up,,, better once hot.

It takes a lot of messing around and a little bit to get it 'right' (and I think I had it right once), but I have found that the .002 feeler, once a feel is gotten for the thing, works and can work just fine. There are feelers with a narrow pointy tip (can't find mine)... Also, setting the pot on the TPS matters .32 to .36 if I remember what I've been taught. Then, the little bushings matter. Then, lol, making sure you secure the little locking nutts on the butterfly adjustment screws before driving MATTERS, hahaha,,, ask me how I know!!! And the setting of the little gap at the place of the capstan stop matters... Still struggle with that and the setting of the throttle arm adjustment. Its a LOT of moving parts and connections.

I have the AAV (which I would either like to do away with OR replace with a new unit) and the cross pipe. I have no idea how to begin to use the vacuum tester folks are talking about but am sure I will learn some day. Maybe I SHOULD be thinking about having the intakes for the beasts breathing be separate on the two intakes...? Maybe, but not this season

 

I'm not entirely sure what Jaguar were thinking when they introduced the balance pipe, perhaps it is the single AAV that instigated, everything I read about the AAV would indicate its necessity on a cold engine and yet so many reckon you can get rid, so either theirs weren't working and the throttle linkages etc are incorrectly set.

The workshop manual starts by telling you to unset everything and then go back through in a sequence, seems fairly straightforward but I'm sure there will be a challenge or two, half of me wants to leave alone as the car runs lovely, but I can't recommission and leave it alone.

In multiple carb setups we use a vacuum guage to ensure that each carburettor is sucking an equal amount of air although it can tell you much much more, it isn't as complex as it sounds. In any system that has mechanical linkages wear and tear play a big role, those bushes on the throttle linkage on the V12 should be considered service items because they will have a massive impact, experience is needed to decide the point at which no matter what you do getting it any better just isn't happening. I'm under no illusion that I've a lot to learn about the V12 in the XJS I have, it isn't simply about measuring - you need to apply mk1 eyeball to what is going on, this is where books don't help and experience takes over.

I've bought so many feeler gauges and yet right now I couldn't tell you where a single set is, I am in a perpetual lose buy cycle and it doesn't seem to matter how I try to discipline myself, I simply don't use them often enough to remember which particular safe place I put them - I write everything down so I don't forget and then forget where I wrote it kind of thing.

Hesitation moving away from idle is nearly always timing or an incorrect mixture on fuel injected systems, often caused by an air leak or low fuel pressure, a vacuum guage can tell you a lot, this is a list of things that a vacuum guage can tell you and why it should be considered an essential toolkit item - along with a compression tester and fuel pressure tester. Good mechanics don't guess, they use the appropriate tool for diagnosis be that a stethoscope or a laptop.

1. NORMAL READING: Needle between 51-74 kPa (15-22 in-Hg) and holding steady.

2. NORMAL READING DURING RAPID ACCELERATION: When the engine is rapidly accelerated, the needle will drop to a low (not to zero) reading. When the throttle is suddenly released, the needle will snap back up to a higher than normal figure.

3. NORMAL FOR HIGH-LIFT CAMSHAFT WITH LARGE OVERLAP: The needle will register as low as 51 kPa (15 in-Hg) but will be relatively steady. Some oscillation is normal.

4. WORN RINGS OR DILUTED OIL: When the engine is accelerated, the needle drops to 0 kPa (0 in-Hg). Upon deceleration, the needle runs slightly above 74 kPa (22 in-Hg).

5. STICKING VALVES: When the needle remains steady at a normal vacuum but occasionally flicks (sharp, fast movement) down and back about 13 kPa (4 in-Hg), one or more valves may be sticking.

6. BURNED OR BENT VALVES: A regular, evenly-spaced, downscale flicking of the needle indicates one or more burned or damaged valves. Insufficient hydraulic valve tappet or hydraulic lash adjuster clearance will also cause this reaction.

7. POOR VALVE SEATING: A small but regular downscale flicking can mean one or more valves are not seating correctly.

8. WORN VALVE GUIDES: When the needle oscillates over about a 13 kPa (4 in-Hg) range at idle speed, the valve guides could be worn. As engine speed increases, the needle will become steady if guides are responsible.

9. WEAK VALVE SPRINGS: When the needle oscillation becomes more violent as engine RPM is increased, weak valve springs are indicated. The reading at idle could be relatively steady.

10. LATE VALVE TIMING: A steady but low reading could be caused by late valve timing.

11. IGNITION TIMING RETARDED: Retarded ignition timing will produce a steady but somewhat low reading.

12. INSUFFICIENT SPARK PLUG GAP: When spark plugs are gapped too close, a regular, small pulsation of the needle can occur.

13. INTAKE LEAK: A low, steady reading can be caused by an intake manifold or throttle body gasket leak.

14. BLOWN HEAD GASKET: A regular drop of fair magnitude can be caused by a blown head gasket or warped cylinder head to cylinder block surface.

15. RESTRICTED EXHAUST SYSTEM: When the engine is first started and is idled, the reading may be normal, but as the engine RPM is increased, the back pressure caused by a clogged muffler, kinked tail pipe or other concerns will cause the needle to slowly drop to 0 kPa (0 in-Hg). The needle then may slowly rise. Excessive exhaust clogging will cause the needle to drop to a low point even if the engine is only idling