I’ve followed at times, discussions on this “quaint” device.
Removing the mystery eluded me for a time. But, I think I got it. It merely adds air to a cod engine. What does that do? It increases the idle speed.
Why? Driveability. Fire up, drive away, no warm up needed. No stall provided.
Older USA carb critters had a fast idle cam on the throttle shaft Engaged along with the chole valve. Mixture enriched and more of it to make a cold engine driveable. As the enmo went upo, the choke opened and the cam was disengaged.
EFI seeks to do the same, but in a different manner.
I’m tempted to temporarily replace the AAV with a cable pull heater valve. That way I could adjust the air like an old school choke. Does anyone know if this has been attempted before?
I don’t know about you, but when I get to the point where I want to modify the design in order to make it work. I stop for a bit regroup; then reassess.
Have you checked the system for intake leaks other intake leaks (not associated with the AAV)? My Not so good deal - '86 Series II had intake leaks pretty much everywhere. I’d close off the air source; and it kept on running - go figure.
@MLee, I’m thinking of using the manual valve as a troubleshooting step before buying the OEM part. I’m afraid I could replace the valve and then discover another issue. I’m not sure how to gauge if the engine is worth putting more money in it.
Money and Jaguars…
It’s a losing battle. I picked up a '86 XJ6 for $400.00 didn’t run. Interior really dry but decent. body straight no dents minimal rust in the usual places - not enough to scare me away.
I got it running by replacing the coil. engine is a bit rattley. Popped off the cam covers to discover the timing chain was loose. OH, and the previous owner had the battery hooked up backwards, so when I tried to start it; it cooked the factory radio - bad day.
What else?
suspension bushes front and back
master cyl
rear brakes ( might as well do all of them)
head liner (sagging)
tank switch broken
Right passenger door won’t open from the outside
rear springs sagging
That’s just off the top of my head. my point is these cars are a money pit; if you’re not handy, and don’t know where to look for parts. Most of the normal wear and tear items can be had from rockauto.com & partsgeek.com. Other parts I get from everydayxj.com and terrysjag.com, xks.com, jagbits.com, sngbarratt.com. Find a local Jaguar club and join. there is a wealth of information available via the members.
These cars are a labor of love and foolishness. I say foolishness because they will suck the money out of your pockets faster than a teenager. Like teenagers you love them cause their your kids, I can’t put a price on my kids or my Jags.
from reading this thread it sounds like you’ve tested it and it is working as advertised on the bench. get a can of carb cleaner or ether. fire it up, and systematically squirt the cleaner / ether around the intake area. if there’s a leak, the RPM’s will temporarily run up. then back down. my '86 XJ6 the $400.00 one had intake leaks all around the fuel metering system as well as the throttle body.
I have 4 XJ’s and 3 XJ-S’s the mostly clapped out cars that I’ve saved from the crusher. Not one have I had to deal with the AAV. Seriously consider OTPubs.com order the XJ manuals. under supplementary documentation there is a training guide for all aspects of the car. I have found the training guides to be worth every $$$.
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The AAV is basically an automatic cold start devise, Adam - also ensuring that the engine doesn’t stall early in the warm-up phase…
Doing it manually; when starting, you have to get the opening correct, relating to engine temp - if not; the engine will baulk. In theory; slightly opening the throttle will have the same effect - getting it wrong; the engine will baulk. So the AAV is there to eliminate driver error - strict ‘feet off’ is called for…
Basic test of AAV function; with the engine hot, verify the AAV and set idle to spec/liking - let the engine cool. Start engine and observe rpms - it should be 200 - 400 rpms higher than hot set idle (somewhat dependent on actual engine temps - which decides slide opening). Idle the engine while watching rpms - which should gradually drop as engine warms up, settling at hot set idle…
If this is so; any starting issues is not due to the AAV. If AAV is malfunctioning; the first step is to ‘massage’ the slide manually by moving it repeatedly with a small screwdriver. When pushed open the slide should spring back to original position - some CRC may help to clear motion.
While the AAV is a ‘non-repairable’ item; it can be dismantled for cleaning by drilling out the 4 rivets. After cleaning, it can be reassembled using screws…
There is no point in replacing the AAV unless it is verified faulty and unfixable - and manual control is not encouraged…
I fully understand your frustration with new problems constantly appearing. It is important that faults are properly identified, before remedial actions are taken - one fault at a time, always bearing in mind that identical symptoms may have entirely different causes. Nor does it help that while testing and accessing; the ‘fiddle factor’ rears its ugly head - you inadvertently touch something sensitive. Or the repair is inappropriate - not addressing the real fault…
I tested the AAV off of the vehicle. The slide moves smoothly but it doesn’t seem to respond to cold. I put it in my freezer for a few hours and slide was in the same position when I pulled it out as it was when I put it in. It reads 22 ohms across the terminals and I believe it’s supposed to be around 30. So I think it’s safe to say that the valve is bad. It seems to always be in a half open position.
Adam,
Then the faulty AAV is the reason that you have been having hot start problems. You said that you tested it and it was always in the half open position and when warm it is supposed to be closed. So I believe that the mixture was too rich when the engine was started warm. In addition to causing warm start problems the rich mixture would decrease fuel economy and increasee emissions due to over fueling. Do you live in a location that requires emissions tests? If you do it is likely that your hydrocarbon numbers are higher than they should be.
Paul, wait, am I missing out on something?
The AAV provides metered air to compensate for drag; wouldn’t it simply give higher idle and less engine braking (unless adjusted with the idle screw, then messing up… mostly cold starts I guess?) and not influence mixture?
I think the ECU gives longer pulses when the sensor says cold, so enriching the mixture, and of course there’s the cold start injector.
I have two bad Aux Air Valves that I need to replace. Searching on the web hasn’t been very helpful for finding a replacement. I found a few used ones and a few sites with back-ordered valves. I was wondering if I could use a newer AAV that Bosch makes. I found this one on Amazon:
Adam,
The Auxiliary Air Valve (AAV), also called the Extra Air Valve (EAV) by Jaguar sometimes interchangeably in the same document, is Jaguar part number EAC3883.
If you search on eBay like I just did you will find at least 5 of them for sale ranging in price from $60-500 US. The most expensive one is new, the rest are used. You will have to use a search like “Jaguar XJ6 air valve” to find them because sellers call them different things in addition to the correct part number EAC3883.
If you don’t see anything you like there I recommend that you try David Boger at EverydayXJ. David is a member of this list and a Jaguar enthusiast. As a part time job he buys up Jaguars, takes them apart, and sells the parts on eBay as well as through his own website. David lives in North Carolina USA and is a great guy. If you don’t see what you need on his website send his an email. He gets cars all the time so he probably has what you need even if it isn’t listed on his website. I have purchased dozens of parts from David and I have always been pleased with the parts and service that I received. He has a full time job otherwise and gets busy sometimes so if he doesn’t get back to you right away just be patient, he will.
I think that trying to use an EAV/AAV other than the one that was originally specified for your car is opening up Pandora’s box to a host of unknowns. I wouldn’t recommend it, especially with the original correct parts available.
When slide has reached some position ‘cold’ - it doesn’t move much further when cooled further.
Ie; ‘open’ at ambient temps, open a wee bit further from the fridge - and then unnoticeable further from the freezer. The gist is that when put on a hot kettle lid from either situation - it will gradually move to ‘closed’…
If it does this; it is fully functional - and not the cause of your problems.
The gist of it is that with the slide closed; it plays no part in starting the car. AAV only plays with the engine ‘cold’ - when it must be open…
And the AAV plays no part in mixture control! That is the domain of the ECU and CTS combination. With some independent fuel delivery from the CSI/TT…
@Frank_Andersen and @Paul_M_Novak, thanks for the feedback. I tried to cool the AAV but not heat it up. If I understand you correctly, “open” doesn’t mean 100% open it could mean 50% open. However, “closed” should be 100% closed. Is that accurate? Also, the hoses to my AAV are old and brittle needing replaced. Can they be replaced with standard vacuum hose or does it need to be replaced with the original tubes?
I didn’t try to heat up the AAV. I’ll do that today and see what happens.
The EAV/AAV closes not only due to conduction heat from the coolant raIL but also from the heating of a resistance coil inside by 12V DC. When I have tested them I have used both methods, as well as cooling in my small garage refrigerator to make sure that the slide closed and opens.
Those two hoses (EAC1596, EAC1471) are modeled rubber shaped like a twisted L or W. I don’t think off the shelf straight hose would do well in this application, especially with the hot engine bay temperatures. Those hoses are readily available for about $20 US each from a number of sources. I am certain that someone has probably used generic hose and maybe it even worked. But I would personally use only the correct molded hoses especially since they are readily available and not that expensive.
I wanted to update the post for the benefit of the group and anyone who is having similar issues with their XJ6 not starting well. Thank you to everyone who offered advice and assistance.
Below is the final resolution to the problem and everything I tried to fix the issue in the order of execution.
Checked compression (125 - 130 PSI on each cylinder using a cheap 20$ compression gauge).
Verified fuel pressure at the injector rail.
Changed the Coolant Temperature Sensor (CTS)
Verified Thermotime switch and Cold Start Injector (CSI) was working correctly.
Replaced all spark plugs, wires, cap and rotor.
Gapped the throttle body (.002 inch)
Verified functioning Auxiliary Air Valve (AAV).
Replaced both rubber hoses on both sides of the AAV
Verified a good ground on engine and frame.
Replaced the installed coil with a PerTronix 40511 Flame-Thrower Coil.
Tried to adjust the timing.
Swapped the OEM distributor with a Pertronix D177600 Flame-Thrower electronic distributor.
As soon as I replaced the distributor all my starting issues disappeared. The XJ now starts immediately on every try and seems to run much better than before. I didn’t know how to effectively troubleshoot the existing distributor. I read so many great reviews on the Pertronix and my frustration level was very high so I decided to go for the complete swap.
The only issue I still have is a lumpy idle. I’m not sure how to start troubleshooting that issue. The car runs great going down the road with plenty of power. However, the idle is lumpy. I think it could be related to poor performing fuel injectors. Any thoughts on troubleshooting a lumpy idle?
Adam,
There have been many posts about idle issues on this list. One lister did a thorough investigation and posted about his work. Search the archives for “lumpy idle Ted Macklin” and you will find a lot of helpful information.
Injector cleaning might make a lot of sense if it’s not false air.
We have a very competent lister who cleans injectors but I‘m afraid I forgot his name.
