I need some help. I have some limited mechanical knowledge, but I'm new to the XJS.
My V12 runs fast at about 1,200 RPM when hot. It can run over 35MPH Without touching the gas peddle and is hard to hold at the stop sign. I tried to adjust the AAV, but I did not see any difference. Is there anywhere else to adjust the RPM?
The car has about 66,000 miles.
Any help would be appreciated.

 

enter the XJS Guru's.....

 

Thanks Jim!
I meant to ask. Should the AAV only be adjusted when the engine is hot!

 

Here's an AAV primer from another site........hope it helps!

Jaguar Auxiliary Air Valve

Sometimes a light "tap" a few times on the AAV is all thats needed.

 

Also check that the throttle valves are adjusted properly and the throttle bushes are in place! .002" clearance.

 

Thanks, any place I could read more on the throttle valve adjustment? I guess I know less than I thought? My experience is limited to carburated engines in Camaro's and Corvette.

 

I also read on that same site about a place to use an Allen key to adjust the trottle. So is there 2 places, the AAV and the Allen bolt or is the Allen bolt on older version of the V12. Mine is a 1990 and I have had no luck in locating it.

 

I think there was an allen key adj on my XJ6, III 4.2litre.

Here's more....V12 JAGUAR THROTTLE LINKAGE ADJUSTMENT / AJ6 Engineering

Make sure ALL your vacuum pipes/attachments are ok and your x-over pipe is tight on all three attachments with no leaks/crackjs in the rubbers.

 

Still at it! Found a few clamps loose on the vacuum lines. I also noticed on the back of the right hand air filter, the supplementary air valve is fitted in the air filter with electrical tape around it. Should there be a rubber grommet there? If so where could I find one and what is the part number?

 

Finally found the problem. It was the Auxiliary Air Valve. I warmed up the engine, took the left filter out and plug the input to the AAV and the engine RPM dropped to about 800. I couldn't have solved it without the forums posting on file. Thanks.

 

Brayon, just curious, how well does it cold-start with the AAV plugged? My AAV is broken...I've rigged up a replacement that adds about 200 RMP during warm up. I then have to remember to shut it off (my 45 second timer is kaput too).

Thanks,

John
1987 XJ-S V12
63,000 miles

 

John, how did you rigged that? The test I found on the internet said to test when the engine was warmed up, so I never tried it cold. Temperature here is the 80's, could be different than in Indiana. I should try that. There is serious suction when you plug it. The other issue would be how would you adjust your RPM.

 

Brayon,

First of all, I lied :-), or rather, got confused. My AAV is questionable, but my SAV was definitely kaput. The car never had a problem starting during the warm months, but now that it's cold again I really had to work the throttle for about 30 seconds or so to keep it going.

My temporary answer is pictured below. This is a pic of the right side of the engine compartment. You'll see a hose coming from under the large silver piece (part of the cold air inlet). The end of the hose you can't see attaches to the large port on the bottom of the right hand throttle body. The hose "tees" into an electric air valve that is supposed to go into a Mazda. At the other end is a yellow filter which is open on the right side to let engine compartment air in. The whole arrangement is somewhat sloppy, but those are the parts I had on-hand.

Since my 45 second timer is also broke, and I've removed the cruise control with no intention of ever putting it back in, I've wired the air valve to the cruise control on/off switch. This is just a temporary expedient until I come up with a 45 second timer.

I've found that with this arrangement I get about 200 more RPM right after start with the air valve open. Having said that, I have also found that I get about 300-400 more RPM by just having the the hose open to the atmosphere, i.e. no air valve or filter. The air valve may be a little small...not letting enough air in...and when I redo this modification I'll use a larger air valve and a larger filter.

As I said, this is a temporary measure until I can come up with something more automated. If your 45 second timer still works you can use it to open/close the air valve.

FYI, when I had my AAV out, I soaked it in cleaning fluid and had it working pretty well...when I'd stick the bulb end into hot water I could watch the piston move as it's supposed to. I could be that it's just about worn out, in which case I'm happy being able to get some extra air into the engine with the makeshift SAV, otherwise I'm not sure what I'd do.

Thanks,

John
1987 XJ-S V12
63,000 miles

 

John,
Great solution. I like to see how different people find different ways and different parts to solve a problem. Thanks for sharing your work around solution. I found a new AAV at JAGUAR Parts and Accessories | JaguarMerriamParts.comŽ , but they cost close to $400 for my 1990, I think it was around $300 for before 1989. So, I'm still trying to get my AAV working again.

Good luck!