I have been looking at extending warm up time on EAV by adding a 17 ohm resistor in series with power lead from Fuel Pump Relay. Currently AAV is 33 ohms and I get about one minute before the EA Valve begins to close from heating electrically. See Diagram below.

Question 1. What would be a acceptable resistor specification? 50 volt, 17 ohm, 5 watt ???
Question 2. Does anyone know why the "ground" wire goes to the ECU and is listed as a AAV (in) signal ?
Appreciate any thoughts from Arm chair Jaguar Electrical Engineers!
Rgds
David

 

For question 2, the air valve gets power from the ignition through the fuel pump relay when it is energized. The ground is through the ECU, so the power is an input to the ECU, when then turns on or off the ground path as needed. It probably ensures that if the fuel pump relay should stick closed when the ignition is off, then the heater in the air valve doesn't stay on.

 

Project update:
Installed 20 ohm 11 watt resistor in series with heating element wire to Extra Air Valve. Warm up time has gone from (1) minute to over (8) minutes at ~1250 RPM in Park.
Restart after coolant temps reached normal range, was with out extra air, and solid 725 RPM idle in Drive with brake on.
Warm up time is longer than I wanted, so have ordered a 10 ohm resistor and will install when received.
Installation is with spade connectors, so can remove in summer if need be.
Will update after next test.
Rgds
David

 

Hi David

Forgive my ignorance but why would you want to extend the warm-up time.

Probably a daft question but I'm not proud!

Cheers

Mark

 

Mark,
Could be just a quirk in my car, but stumbles off idle till needle gets to about 1/2 way on temp gage to normal. So, with one minute of extra air, I have stumbling and cut out for about 4 minutes at stop lights etc. Idle is in low 600s RPM until warm up (once warm is a solid 725 RPM). I normally start driving after start, when the Alternator needle begins to move. I let it idle for 8 minutes once resistor was installed, just to test time to close electrically.
Currently car responds nicely to low speed city driving just after start, but I think 8 minutes is too much.
I had switched from 20w50 oil to 10w40 for winter driving, but still had the the slow warm up.
Like several other Jaguar owners I know, I may just have too much time on my hands???
Rgds
David

 

Have you checked that your car has the capacitor mod in the wiring to the AFM? This is designed to improve running (especially idle) during the warm-up cycle. See details in this link:

https://www.jag-lovers.org/xjlovers/xjfaq/efiover.htm

 

Yes I installed, I saw that recommendation shortly after I acquired the car. I have not touch AFM itself, as I did exchange for an Overhauled Unit during recommissioning. ECU is original, have thought sending my spare to UK for reconditioning and updates, but haven't pulled trigger on that project.
Rgds
David

 

Project Complete:
Removed the 20 ohm 11 watt resistor (replaced it with a 10 ohm 10 watt power resistor) in series with heating element wire to Extra Air Valve. Warm up time (higher idle RPM) has gone from (1) minute to (4-5) minutes at 900 RPM in Drive with brake on. Very good for early morning stop and go driving. Will see how it feels this summer.
Rgds
David

 

Hi David,

Very interesting project, looks like its worked well!

I'm interested in how you were measuring when the extra air was fully closed, was this by noting when the idle got back down to a particular figure?

I'm considering a bit of a modification on mine because the bimetallic strip has become quite tired with age. It nether fully closes nor fully opens the shutter for extra air.
When warm I am still left with the slot in the shutter showing.

My modification would be adding of material to the shutter where it contacts the strip. Thus adjusting how closed it is.
It doesn't get too cold here, so I'm not overly fussed with the lost openness that this modification would create.
A little extra air when cold would be nice, and fully closed would be great when warm.

My thoughts are to modify it (in a reversible manner) so that the shutter is fully closed at the same temperature that the thermostat opens.

H.

 

"I'm interested in how you were measuring when the extra air was fully closed, was this by noting when the idle got back down to a particular figure?"

Harry,
Yes I was watching peak and low Idle RPMs to determine full range function of extra air valve. Mine seems to be free to move full travel. I considered injecting solvent into the rubber hose attaching to valve to clean internally, with a Hypodermic Needle, with engine running; but seemed cleaning wasn't necessary.
Internal cleaning may get you back to full travel.
Rgds
David