This one is driving me nuts, 1st no idle adjustment, removed and tested AAV=good
Cold start Jonas loda told me to plug AAV and see what idle was=750 RPM. UnpluggedAAV. 1100rpm, now the fun started. As engine warmed up the idle began to drop but then suddenly went up to 1700 for about 1 minute, then the idle began to surge as the ecu started doing its job. Vacuum leak right? All new hoses, now idle is 1100 and not adjustable- and she steadily begins to climb in rpm’s as it warms up. Removed the vac adv and engine settles to1100. Put vac back on and 1700 and begins to surge.
What I have done: proven AAV is good
Replaced vac lines
Set throttle plates to .002. Sync linkages
Throttle bushings
Proven SAV and hose is working
Reset ECU
TPS set to .34 v and tested to WOT 4.97 v
Eliminated vacuum line to cabin controls
PCV good
Crank case breather good
Sprayed intake and throttle bodies while running and no change
Distributor cap. Check vac advance and weights
Vacuum line to trans modulator - good
Line to ecu good
Vacuum advance holds vacuum but when connected raises the rpm’s to 1700
23000 miles on this car she sat for 5 years we got her running and driveable but the idle issue always bothered me.
The stickers for routing houses are useful but I don’t necessarily know the exact names of the parts.
Sorry for the long post.
Is there anyone that has an idea or seen this issue before?
Does anyone have actual photos of the vac lines connected properly? This is a USA car
THANK YOU FOR ANY HELP
Harold
Sounds like a vac leak still. A dicky PCV valve possibly. One of the symptoms of a failing PCV valve is over revving.
I’ve not vacuum checked it. I just rattled it. And plugged it while the car was running. And no change.
Thank you for the reply
That much increase doesn’t sound right to me.
Mulling required.
What’s your base timing set to? SB 18º at 3000 rpm
Is there any chance the mechanical advance is sticking, perhaps not consistently? I’d be inclined to triple check
With AAV plugged you should come down to 400 rpm or so
Did you clean the throttle bores?
What happens if you disconnect the linkages rods? Does the problem change in any way
Cheers
DD
Thank you, I’m going to go after the distributor tomorrow and take a much slower look. Timing was my next job. Although I am not sure how it would change.
Linkages off is the same.
Is there a site that has comprehensive photos and explanation of correct routing of vacuum lines?
Check also the overrun valves.
Disconnect all vacuum lines plug all ports and see what happens.
Maybe you forgot to plug something?
This doesn’t sound correct to me either.
Maybe the delay valve, solenoid or something in that circuit is leaking?
How did yo test the advance capsule?
To have 1700 rpm idle you have a big leak.
Check also the Supplementary Air Valve and the Cruise Control.
I will plug all lines going to overrun valves this afternoon and try that. Thanks
I have gotten "lost a bit on the vac lines as there are more components under the hood than I can find online. The stickers under the hood are not legible. This is why I was hoping someone had photos of their good running XJS with the correct routing. All hoses are connected.
I pull vacuum on the advance and watch the capsule move, I also add vacuum while its running and the idle goes up.
SAV was removed, hose to air box removed and checked, solenoid checked with voltage input and vacuum applied.
ugh…
I’ll check the Cruise bellows later also
Thank you Bob, I have this one, BUT The full throttle switch has a T in it that goes back through the fire wall. That isn’t shown here.
and it seems as though I can’t locate the “solenoid vacuum valve” which i am assuming is electrically activated after 45 seconds.
Is the “full throttle solenoid” blue and white? 2 wires connected at the back of the A bank?
and are the “Thermal Valves” located low on the A side in the coolant rail
I have longer lines on it just to make it easier to find the correct routing, they will be trimmed and properly put away when I’m done.
On my '87, there are three vacuum hose diagrams on the bottom side of the hood. They ought to be close to how your '89 is supposed the be plumbed. Hope they help.
This is my issue. My 89 has a 3 line thermal vacuum valve that is not shown. As well as the 2 post electric solenoid vacuum valve. As seen in my picture in above post.
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So…… that’s what those labels are supposed to look like. 
. Here’s what I did today,
Removed distributor cap and checked all internals= good
Reinstalled and check leads were in the correct order= they were
It seems I had 3 things wrong with my work…… 2 delay valves were backwards.
1 vacuum reducer was not inline.
Started and checked vacuum at the ECU=12”Hcg ( is this right?)
Idle was 1000 climbed to 1200 as it warmed up.
Connected vacuum advance and rpm’s went to 1400…. I’m getting closer.
Plugged overrun valves. No change
Went through the throttle linkage settings again from the beginning…. 800 RPMs!!! Reconnect advance and now I’m at 900 rpm’s. There is no vacuum at the AAV intake but the screw is out 1 turn. No difference if I turn it in BUT there is a difference If I open it. (Yay)
While checking in the trunk(boot), I found a very small hose end staring at me. I pulled it out from around the fuel reserve canister. It seemed to not be attached to anything. It’s about 18 inches long. I thought there was only supposed to be one line in the trunk, ideas?. Tomorrow I’ll set the timing but man does she run nice now. Engine is not running hot at all. No hesitation and no pinging. Thank you for the legible labels. I now have printed them and put in my service file along with 100 other pages.
That small line in the trunk could be the battery vent line. Is yours hooked up to the battery. If you have an AGM battery, there’s nothing to hook it up to.
I don’t have the original typ battery. That makes sense. I read somewhere about a vent line