Cleaning out the secondary air rails?

Andy - I got that fingers-crossed maneuver down pat.

Steve - -right you are. I think that owning a Jag is a life of mission creep. Had a boat once - - a hole in the water to throw money in. Now it is a Jag :slight_smile:

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Yup… same story here Andy.

I cannot say, however, that this is the first time I see CEL



PS The air rail will have to check valves in the back, which will be rusted/gummed up. Standard GM product that costs a few dollars. BTW, the o-rings for this application are not critical, one can argue…

Hey Steve - - so you just took the secondary check valve to your Autozone or whereever and they could match it to a GM part? Sounds great . I got the air rails out - - lots of penetrating oil and constantly wiggling pulling etc for 2 days . They don’t look too bad - - except the check valves are pretty rusty and let air go both ways. Still trying to break the connection between them and the rail. Pretty frozen on there :slight_smile:

Sounds familiar Jim… :slight_smile:

Regarding the check valves – yes, this is what I did. I walked out with a Dorman 355050 which is the generic equivalent of GM/ACDELCO 19307616.

The list of cars from 1966 until the mid 1990’s this check valve fits is amazing.


PS. I ended up using heat on it. After that, the rail was painted black. Sorry, cannot find a picture

Steve, I got the Dorman 355050 valves in the mail. Funny thing I noticed - - the tube on these valves, that inserts into the y-hose, is slightly smaller outside diameter than the ones that I removed. But since the secondary air doesn’t appear to be a “critical” pressure joint, on that side of the check valve, I plan on cinching down the hose clamp. If need be, I might even put a couple of wraps of duct tape on the tube to ensure there is enough meat for the hose and hose clamp to make a decent clamping



Update to the thread I started. I got the secondary rails cleaned out - - thx Steve and Paul for the tips regards using a drill bit. I also found some pipe (tobacco type) cleaners that had copper bristles mixed into the cleaning surface. I soaked the secondary air rails in gasoline after drilling and blowing out with compressed air – and then stroked with pipe cleaners the next day. and blew out again with compressed air. The check valves that were on the removed rails were, as Steve predicted, no good anymore. You could blow air through in either direction. I did not however, choose to pull the secondary air pump or tubing between it and the new check valves.

In the meantime I had sent the injectors and fuel rail to David Faircloth fo Jaguar Fuel Injector Service for injector cleaning/servicing and had the fuel rail painted Red. Great job David !! Thanks a bunch. David also grouped the over-hauled injectors for me so I have the least amount of standard deviation between injectors per rail. Liberal application of 3M silicone based oil on the o-rings and the injectors mounted easily to the rails, and then the “mounted” injectors slipped right into the manifold. Had to wiggle a little here and there lining stuff up but the fuel rail and injectors slipped into place and got bolted down. (Note to self - - be glad you have a post facelift and don’t have all those little rubber fuel hoses to the injectors to have to deal with)

Also took the time at this juncture to remove throttle pedestal, cruise control bellows and coils, clean the top of the engine, and replace the sparkplugs - - used (again) a set of Bosch Platinum 4+. Liberal use of Dielectric grease on plug wires (each end) and all electrical connections affected.

While reassembling determined that one of the check valves for the secondary air had buggered up threads and wouldn’t screw onto the rail – so had to swap it out - - ended up with one Dorman check valve (painted black) and a BWD in silver. Getting the air rails back into the holes was more of a challenge than the injectors but finally got the stars and moon aligned and got them cinched down with new o-rings in place. (Thanks GCODER1 – 010 size was spot on)

All back together and runs !! Yeah. Need to put through some driving cycles to see if the dreaded FF67 shows up again.

Oh BTW - - double-checking the connection between dizzy and coil HT wiring can prevent head-scratching as to why it tries to start but won’t. A bank to rear coil and B bank to the front coil. Ask me how I know ---- I thought I was so careful in putting all the wires back in place

So i will drive a while and see if injectors are next


Meant to say see if the O2 sensors are next.

Three days of driving and so far so good. A little rough, and high, in the idle first day and I adjusted cold idle. Now 2 days later it is sitting pretty steady at 700-750 (slight bounce between the upper and lower readings) this morning after first start. I guess it is re-learning :-).

This has been the subject of nearly 1/2 of my post on JL Jim.
The system doesn’t re-learn. The +/- 50 rpm change is the (slow) response of the ECU to the feedback from the O2-sensors.

Good work!

Thanks Steve
I remember now reading your posts.
Guess the verbiage of the tech update from around 1994, talking about change to fuel to enable adaptive fuel learning

Oops, didn’t finish my earlier reply. Meant to finish with the notion that reading the tech update, after having read your posts and many others, left me thinking of adaptive fuel control, or “learning and adjusting”. I obviously get easily confused. My brain used last in first out retrieval system.
This morning’s cold crank looks good. Still sitting at 700-750. After warmed to Normal, with a/c ON, idle at stop lights is about 850 in Drive. 4 days driving so far and no FF67. Best regards

Hi Jim:
You probably mistyped, but just to confirm. You start the car in the morning. Idle speed (cold) should be 1100-1200 rpm and dropping gradually as the engine warms up.
The normal operating temperature, your idle speed in PARK or NEUTRAL is around 750 rpm, give or take.
WIth the transmission engaged (In D or R), brake pedal depressed your idle speed should be LOWER.

Mine is around 600-650 rpm (but I have never tried with the A/C on – my system does not hold charge and this is one of the jobs that I am not looking forward to undertake).

PS Next time you are ready for an adventure, remove the signal wires from the O2-sensors and start your engine. The idle when it warms up will be smooth, no bouncing. FF44/45 should be displayed but when you reconnect the sensors, the CEL will be gone.

Steve — just cranked it up — cold start; been sitting for days. Cranked right up and Idle at 600 and steady. Warmed up to normal temp, did a couple of throttle pulses up to about 2000 rpm and idle is at 725. I bought the car as second owner in 2002. I do not remember it ever idling at 1000 to 1100 on first start. Always seemed to me (as far as I remember) that it idled pretty close to 750 no matter which start. Maybe idled at 800-900 on cold start.

Now I am curious as to what component could be causing this. Could lack of )2 sensor input cause a low idle on cold crank? I know my wife’s XF idles on first cold start at 1100 and then works it way down over about a minute to minute and half. Same with my Nissan 350. Never even thought about the XJS V-12 other than to adjust the AAV — which i did incorrectly couple of weeks ago. I adjusted cold instead of warmed. Have since corrected tha,t and then this morning did the cold crank I reported above.

I hope I am not giving you wrong info Jim, but the purpose of the AAV is to give the engine more air when cold. RMPs should be higher with more air and fuel.

Mine does go above 1000 upon cold startup and gradually decreases to about 700 rpm at normal operating temperature.

If your cold and hot idle speeds are the same, I’d look at the AAV. Your piston could be stuck in the top position.


Thx Steve. Sounds like a plan.
Best regards, Jim

Not necessarily. There is far more friction when cold, and more of the
energy of the burning fuel is absorbed by the cold cylinder walls. So it would
take more fuel and air to run at the SAME rpm. Plus the mixture needs to be
richer to deal with poor atomization and condensation on the cold inlet tract
surfaces. I agree that cold start systems NORMALLY result in the engine
idling faster than when warm, but it doesn’t really have to – especially with a
V12 that’s not going to stumble.

The design of the AAV port changed many times over the life of the Jaguar
V12, indicating that Jaguar was fiddling with cold idle. I dunno about others,
but I’ve always found a high idle a bit irritating with an A/T because the car
tries to pull away without putting my foot on the gas. Perhaps at some point
Jaguar decided that the idle should be as close to the same idle speed hot or
cold as possible.

– Kirbert

Ever since I’ve owned my car, the AAV has behaved exactly as Kirbert describes- 750 rpm cold, 750 rpm hot. That puzzled me at first, and I gave the AAV the boiling water test. It worked perfectly. The PO had replaced it about a year before I got the car, but whether it was the CORRECT unit for my 87 engine, I don’t know. As I like a slightly faster idle when cold, I put my unused thermal vacuum valve (On the “A” bank water rail) to work, and used it to trigger a 5/8 heater valve, plumbed into the extra air valve line on “A” bank. Now I have a cold idle of 1000rpm, which lasts maybe a mile, then switches off. Works for me!

Ever since I’ve owned mine, the cold idle has been higher.
Perhaps I am the outlier but I never even considered another possibility.
This has been the case not only on the the Jag, but on any other car I’ve owned.
Even my father owned LADA (VAZ 2103) with a carb and a manual choke did it.
Best regards,

I have experimented with this and if you are interested will find the old thread.
Have 2 of all possible designs for AAV.
EBC1198 – specified for the 6.0L V12 and the EAC2273 – specified for the 5.3L at least 5-6 years before the build date for mine.

EBC1198 I have two – one I bought from a forum member here (used) and the original tom my car.
With all the experimenting I have done, cold idle has never been the same as warm idle.


PS I also find the 1100 rpm idle annoying and perhaps unnecessarily hard on the transmission

When I bought my car, one of the first things I did was read “The Book” and try to absorb at least some of the info. it contained. I looked at the various port configurations on the AAV and wondered how an owner could buy the “correct” unit when all that seemed to be available had the same part no.
All my previous cars have had a cold “fast idle”, too, but not my Jag! Now, however, it does!
I bought a used AAV and dismantled it just to see how it was put together, cleaned up the inside bore and piston, and reassembled it. Maybe if I use it in the future I’ll have an actual Jag. fast idle!
( what is LADA (VAZ 2103 )?
Best, Dave.
The only other thought that just crossed my mind is that my car never sees really low temps. Maybe if I started it at 32 degrees or below I’d HAVE a fast idle! (Edit)

From 3 AAVs on my car I can conclude that nothing of significance happened upon swapping the original (and working in hot pot) valve, with another known good used one, with a brand new EAC2273 (cost less that the used one, but still slightly over $200)

I have a suggestion – if we are going to discuss AAVs, let’s do it here:

or here:

Best regards,