Good morning and happy new year,Compliments for the forum

I hope you can give me a suggestion….no one can help me in Italy.

My Jaguar XJ5.3C 1975 has an idle ever too high.

I already change the auxiliary air valve with the stainless steel upgrade but the idle is even at 900 rpm when the engine is hot and if accelerate in neutral, the idle come back to 1.100 rpm!

After accurate tightening of the hoses I find the vacuum leak: on the Air Box of the B bank, the hole connected to the idle valve suck air.

The car doesn’t have a PCV valve on the airbox of the B bank and the breather cap is connected through an hose, directly to the idle valve and not to the airbox.

The question is: very early fuel injected V12 doesn’t have a PCV valve but only the breather cap?

if I put my finger on the hole, the idle goes at 700 (with idle screw completely closed).

I think the hole in the B bank airbox is useful for overpressure from the crankcase, through the breather cap, so the air should be enter in the airbox instead of exit from it.

Thank you in advance for your support!

Enrico

 

Enrico
Can you post a photo of the pieces and area of the engine you are describing?
The pre HE engine does have a pcv , as shown in this photo, but exactly how it is connected I do not know. Grant will be along soon, and he will!:


https://www.ebay.co.uk/itm/277527797...Bk9SR86Ynf_xZg

 

Got it Greg.

Oh Boy, I will think 1st, it will be long, so maybe a PDF, as this system can "time out" the replies sometimes.

I will suggest to the Mods to move it to a thread of its own, as the OP is a 6cyl, and yours is a V12, and there is enough confusion already.

Back later Aust time.

 

Good morning Greg and Thant you for reply,
your picture perfectly explain my doubts: the pre HE has a different path for the hoses, with the cap breather and without the PCV VALVE and n. 4 connection at the Idle valve:

 

Problem solved:
- new oil vapors valve
- new gasket





the idle speed, when the engine is hot, now can be settled at 750 rpm

when the engine is cold the idle speed doesn’t give up, even if I changed the auxiliary air valve, but this is not a big issue.