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Discussion Starter #1
OK heres how it is, my unleaded 1987 Falcon XF EFI, has been up to some really strange things lately. When the car is left in idle for a bit, and has warmed up or is hot, it goes absolutley bursurk, really rough idle, loss of power, and really rich burning fuel smell, it almost seems like it isnt getting the correct fuel to air ratio.....now what happens is when I drive it around (which is obviously what you do with a car) I drive around, and the engine is warm/hot, and it will be perfectly fine, now when I stop at the lights or anywhere else for even just 1 minute, it starts doing it, then if i drive about 3 to 4 km with about half acceleration (pedal pressed about half) then it clears up and drives normal again, but if I stop and idle again, it will come back.

It only seems to happen when the engine is hot (it sill happens on cold days), and it happens a lot faster on warmer days.

And it doesnt just happen at idle either, even when I am just cruising around the suburban streets at about 30km/hour.

The most weirdest part of it all? I could drive all the way to Phillip Island on a 35 degree day (its about 1.5 hours from my house), and as long as I dont stop/slow down it will not do it at all.....it stays normal, but the minute I stop for about 2 minutes at the traffic lights it starts it.


Can anyone provide a diagnosis on this? It baffles even the pros, or so called pro's at Ultra Tune and mechanics etc. Anyone had/has a similar problem?
 

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I had a very similar problem on my unleaded carby XF - i.e. it would drive fine but would not idle. In the beginning the problem was intermitant but became worse very quickly. After trying everything (spark plugs, leads, fuel pump, carby overhaul, etc) and suspecting a burnt valve someone suggested taking the rocker cover off and watching the engine idle. By doing this I was able to see very clearly that one valve that was not operating fully. I pulled off the rocker, removed the pushrod and then pulled out a very mushroomed hydraulic lifter. A secondhand lifter cost me $2.00 from the wreckers. But this is only probably a short term fix as CAM wear is the most likely cause. So I can probably expect the lifter to wear out again or the CAM to wear down to the point that it is round. I hope this helps.
 

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Two SC 61's = trouble
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Don't know much about that model.But i'd check cold start or air temp senser, water temp senser as well..Map maybe R.S if it has one.Make sure vacuum line to map is not leaking...Check t.p.s...Air cleaner...
 

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Discussion Starter #4
Thanks mongoose, but I dont think it is that, as if it was it would be idleing really rough even when I first start the engine, and wouldnt come and go with the heat, long idleing etc....

There are three things which I think it may be:

1) The temperature control sensor is faulty.
2) The vane meter sensors are gone, and the whole unit needs to be replaced.
3) The computer chip (the one in the passenger kick panel) is faulty.

It even does it if I don't even drive the car, I can start the car, leave it in idle in the driveway, and if it idles for about 10-20 minutes, it starts....if its hot weather it happens even quicker.....

Anyone?
 

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Pursuit Reincarnation Dog
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I like the lifter idea because at idle with hot oil the lifter will bleed down more easily. Then when you rev the engine again and the oil pressure increases the lifter gradually bleeds up again. Judging by the other symptoms I'd be guessing it was an inlet valve lifter (the lifter and cam wear is very common on the XF engines).

I make the above statement assuming the current mechanics have checked the fuel system regulators, valves, purges etc.

One other thing, the EFI engines will run rough and cough and splutter if there is a crankcase air leak. You can prove this by loosening the oil filler cap whereby the engine starts spluttering and will sometimes eventually stall. Check the crankcase seals such as opil cap, PCV valve seals etc etc.
 

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Also, my experience with the lifter is that it wore more on one side than the other. So, at times, when the lifter rotated in its bore to its good side the engine would run fine. Sometimes it would run fine for hours. This why I found it so hard to diagnose the problem.
 
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