Idle problem '89 xjs

(sloth) #1

Engine starts fine and warms up around 10K rpm… then when warm it goes to very lumpy idle like needing more air (or fluid). Before I start pulling the air valve what simple area should I investigate? The bolt on the air valve is doing nothing either fully in or out.

Second issue…Where is the buss bar on my '89 xjs…?

(scrimbo) #2

on firewall behind valve covers…encased in vinyl with exposed ends…be carefull.

(Paul M. Novak) #3

Have you checked the condition of your throttle shaft bushings and are your throttle butterflies properly adjusted?


(Greg) #4

I’m sure you have checked, but, based on symptoms…what about Coolant Temperature Sensor?

(DavetheLimey) #5

Type “Testing AAV” into the archives. There you will find at least 50 responses. That should help.

(Robert King) #6

Read the thread I started titled “45second timer”, may help you with things to try. Greg suggested the CTS, simply short the connector terminals together for the ECU to think engine is at operating temperatures.

(sloth) #7

Thanks for the info. I checked the CTS and used your suggestion…When back at the ECU I could not find the 13th and 17th terminals since there was no numbers as a reference.
But I kept checking continuity and finally located enough contacts to show the wire was solid and would carry a signal.

Still no smooth idle after warm-up. I replaced AAV, and Cts.
When replacing CTS I noticed no liquid in socket of old CTS. The book I have indicated a loss of fluid when removing old CTS…There was none there…Why…?


(Paul M. Novak) #8

It sounds like the air on your engine was not properly bled out and you have air trapped in your engine. Perhaps this is contributing to your idle problems.

Kirby’s book covers how to bleed the air from the coolant system. The XJ-S ROM also covers and I am certain that the archives have lots of post about this. The general technique is to elevated the front of the car to purge trapped air through the air bleed pipes.


(sloth) #9

Thanks Paul:
I just thought of this idea…could my thermostat (one or both) be frozen shut and not allowing water to bath the CTS and do it’s job???

(Paul M. Novak) #10

Hmm…I don’t think so because both of your thermostats should have the little jiggle pins at the top and so bleed air all the time.

I recommend that you properly bleed the air from your coolant system as described in Kirby’s book or in a more complicated method as described in the ROM.


(sloth) #11

Hi Paul
Where is the best place to test fuel pump pressure?