I'll have to mull that for a minute

Yes.

It's just that ECU/computer failures are a bit unusual so most of us are reluctant to go there until all other choices have been checked and eliminated to the greatest extent possible/practical. Low demand means used units are reasonably priced, though, so replacing as guess is not too painful.

Cheers
DD

 

do you know where the computer is, I think I saw somewhere its in the trunk behind the rear seat

 

Correct.

Forward bulkhead of the trunk, RH side, behind carpeted trim panel

Cheers
DD

 

My gut feeling is that you are correct...but I'm just not sure. With the engine running things might change. others will chime in.

For example, your fuel injectors will show "+" voltage/power on both wires with the key on. But with the engine running the ECU grounds one of the wires to fire the injector. That wire then returns to "+" voltage. These are nano-second events, as you might expect.

Cheers
DD

 

thanks, I'm going to order a computer Monday if no one else has any ideas


I found one for $80 close to me so it shouldn't take long to get

 

i got another computer and that didn't help at all

 

Clamp the cold start injector's fuel line. Any change? Stuck open or leaky CSV.

Has your air flow meter had its top popped off?

Have you looked at the aux air valve? May be plugged up inside.

Hmmmm

 

I had unplugged the wiring from the cold start injector and that made no difference

the top is off and I adjusted it but it made no difference


where is the aux air valve? I will check that out

 

Which suggests there is no electrical malfunction. However it could still be stuck open, hence the idea of clamping it off






Bolted to the underside of the water rail....funny looking aluminum casting

Cheers
DD

 

That is highly suspect. No adjustment will improve the AFM and any existing alterations from a PO are almost impossible to undo. Swap with a known good unit is the only practical option for confirming proper function.

 

I don't know much about jaguars but would this make it run bad just when the engine is cold

 

It would affect it at all temperatures. But your issue is directly relatable to the ECU altering the fueling ( increasing ) to compensate when it senses a cold engine. If your AFM is mis-set then it's misinforming the ECU as to how much air is passing through it. That could contribute to the condition.

Anything that affects the air/fuel mix is suspect.

I think you have inadequate air to burn the additional fuel when cold. And that is more likely the AAV not flowing air when cold, but it could be contributions from multiple slightly off-spec components as well.

 

Agreed, a 'stack up' of faults.

I'd try a known good AFm and, if no joy, go right back to square one, methodically checking ignition system, all fuel injection relays and connections, grounds, etc.

As for the AAV, FWIW, once I drove a Series III for about a month with the AAV removed from the car and the hoses plugged. It ran fine. The only hitch was an occasional stall at idle after a cold start...ambient temps in the 35ºf - 40ºf range.

Letting the engine warm up for about a minute with the throttle held to about 1200 rpm took care of that.

Cheers
DD

 

I clamped off the line to the cold start injector and no change


is there a way to check the AAV to see if it is working

 

There's no convenient way

You'll have to remove it from the water rail so you can look inside the air passage. There's a disc in there that rotates to increase/decrease the amount of air passing thru. More air when cold, less when hot.

Removal is a little tricky as one of the AAV hoses is under the intake manifold. But, the hoses need to be check anyway, right?

Cheers
DD

 

right, I'm going to tare that off as soon as I get a chance


thanks

 

I got it removed, I'm not sure if I broke the hose getting it off or not but either way its brittle and needs to be replaced, how do you get to the other end of the hose, do I need to remove the intake?


I can move the wheel in the aav with a screwdriver, do I just hook power up to the plug to see if its working?

 

Lord no ! That's a huge job.

You gotta get under the car....in just the right position....and you'll see where to disconnect it.

The hoses is a different diameter at each end as I recall. You'll need to order one from a Jag supplier

Note the position of the slot in the rotating disc at room temperature. Then put it in the freezer for a bit and recheck. It should be open wider. The hook it up to the connector and.......

I can't remember offhand what powers up the internal heater. Not sure if simply turning the key 'on' will do the trick, or if if gets voltage from the fuel pump circuit, or what. Others will chime in.

Cheers
DD

 

Looks like voltage comes from the white/green wire of the fuel pump relay. Ground comes from the ECU on the white/pink wire.

You could rig up a bench test easily enough

Cheers
DD

 

I put it in the freezer and if it moved it was a minimal amount, I'm guessing it should open up pretty much all the way


with power it did nothing so I'm guessing its bad