XJ6 & XJ12 Series I, II & III 1968-1992

A little rough on idle

 
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Old 06-19-2014, 11:19 PM
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Cool A little rough on idle

hi
Finally got our XJ6 1986 back today. running well but is taking a little to start and running rough seems to settle after she as warmed up. fuel is more than likely stale so I give it good run once i can fill the tanks. should i run normal 89 or run 91 for a bit.
 
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Old 06-20-2014, 03:22 AM
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I was advised here to run 95 or 98, It does idle rougher on 91. But no real difference between 95 and 98.
I have run a few tanks of each and have settled on 95,seems to work fine.
It does idle better at 600-650rpm in drive,books suggest as low as 500-550 in drive but I find this too slow,giving a rough idle.
It may different with your car as I think it is fuel injection isn't it?
 
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Old 06-20-2014, 05:01 AM
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yep fuel injected. the car has been sitting a while so I plan to do about a six months to tease out any issues. i think i might have to tweak the air flow meter too as it come out of the 1984 model. I am hoping a good run with new fuel and change the fuel filter will make a difference.
 
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Old 06-20-2014, 06:25 AM
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Agreed.

Nothing but our 98 for any of mine. NO Ethanol, EVER.

I would change the spark plugs (if not already done) as well, and make sure the gap is as specified. I THINK???? 0.30".
 
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Old 06-20-2014, 10:47 PM
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I cannot buy any fuel where I am that does not have any sort of blended fuel, what is the ethanol/gasohol or whatever other ecofreak stuff gonna do to my 83 4.2L.
 
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Old 06-21-2014, 12:41 AM
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Thanks Guys.
Just need to wait till we have the money. price of fuel is about 1.80 per ltr here now for 98.
hadnt thought of changing plugs good idea. I'll do it after the first tank load to flush everthing out.
 
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Old 06-21-2014, 04:27 AM
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Just got reminded by Son.

In the boot, behind the rear seat trim vertical panel, sort of to the the right of centre, in an impossible location, is the fuel ECU, and on the side of the ECU is an "idle fuel trim knob".

It can be reached by FEELING in from the left side, and the ECU will be readily felt, then wriggle the hand around and the knob will be felt. It rotates on a "Click" ratchet, and I think? 13 clicks end to end.

Once the beast is WARMED up, give it a twirl, SLOWLY, and see if that "sweet spot" can be dialed in.

His was 4 clicks out, and once dialed in, sweet as.
 
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Old 06-21-2014, 04:46 AM
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Wow did not know that. I'll check that.

Thanks Grant.
 
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Old 06-21-2014, 09:54 AM
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Originally Posted by brianbill View Post
I cannot buy any fuel where I am that does not have any sort of blended fuel,

Been that way up here for as long as I can remember...20 years or so at least.


what is the ethanol/gasohol or whatever other ecofreak stuff gonna do to my 83 4.2L.


From a running/driving standpoint nothing horrible will happen. You'll lose about 3% fuel economy. That's about it.


E10 can be a problem if moisture gets into the fuel tanks, so be very aware of that.


Many insist the E10 dries out rubber parts and has a corrosive effect on some metals. I'm not convinced that this is a serious or widespread issue.....real world experiences vary so greatly.... but there is tons and tons and tons of debate in the archives. Some blame E10 for everything from a drippy fuel hose to their wife getting pregnant

Cheers
DD
 
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Old 06-21-2014, 10:01 AM
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Originally Posted by Grant Francis View Post
Just got reminded by Son.

In the boot, behind the rear seat trim vertical panel, sort of to the the right of centre, in an impossible location, is the fuel ECU, and on the side of the ECU is an "idle fuel trim knob".

Very interesting!

I wonder if this is one of the differences in USA vs. ROW spec cars? I don't recall ever seeing an external ECU adjustment on our Ser III 4.2 cars. The idle mixture is tweaked at the AFM.

Or maybe I just never noticed?

The USA V12s had an external ECU adjustment, though, just like the others.

Cheers
DD
 
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Old 06-24-2014, 03:54 AM
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Checked today, no ECU adjustment. Fueled up today added bottle of injector and fuel cleaner in each tank. Trip home she started to sound better and smoothed better at idle. Purchased fuel filter and plugs.
 
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Old 06-24-2014, 04:49 AM
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Doug,

I reckon you are right. Another '84 S3 6cyl stopped in today, so I clambered in the boot and dug around, NO adjuster.

Challenged the son. He was still convinced it was on his '85 S3. MORE challenge, and I reckon he is thinking of his S2 V12 D Jetronic. AT a stalemate at the moment.

Apologies for any false info I may have posted. I will attend the "naughty corner" with a fresh JD and ponder for an hour or 2.
 
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Old 06-24-2014, 06:42 AM
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No probs. it is always a challenge with jaguars even individual cars of the same year mobley can be slightly different.
 
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Old 06-24-2014, 09:25 AM
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Points:


1. I read the other day that E85 is sold at some locations here in the USA. What I did not realize before is that it is not 15% Ethanol, but 85% Durn near all alky!! And that some very late cars handle it well or at least somewhat.


2. E10 is the fuel of the day around here. No options that I am aware of. My cars do OK with it. My 2 cycle lawn engines and generator not so much. The 4 cycle Honda powered lawn mower does Ok with it as does the Honda knock off predator powering my chipper/shredder.


3. Fresh, clean fuel is the key. Octane to match engine needs. At about 9 to one engines do fine on 87. More #'s and higher is needed.


4. Some engines are octane happy and others not so much.


5. Way back when,. I rebuilt the engine in my 69 FJ40 Toyota land cruiser. I used parts of the 69 engine and parts of a 74. Result, flat op pistons and a small volumn head. Lottsa #'s, but needed 98 to be "happy".


Same with my Edelbrock headed flat head Ford V8. Not happy with less than 98!!




I wonder what my WWII vintage Tecumseh powered generator will think of E10!!


Carl
Carl
 
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Old 06-25-2014, 05:16 AM
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Getting slowly to the problem. Heading to my mechanic tomorrow, we going to run a fuel pressure test, indication is could fuel regulator problems. Getting it up to speed and she runs like dream. Go to turn around and shift gears and it stall starting produces black smoke and struggles to start.
What is every thoughts on the fuel cooler on the aircon. We have had the whole aircon replaced and found out today that they did not add back the cooler.
 
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Old 06-25-2014, 06:27 AM
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I dont use that cooler at all. Never have.

No issues so far.
 
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Old 06-25-2014, 07:46 AM
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Originally Posted by Mad Matt View Post
Getting slowly to the problem. Heading to my mechanic tomorrow, we going to run a fuel pressure test, indication is could fuel regulator problems. Getting it up to speed and she runs like dream. Go to turn around and shift gears and it stall starting produces black smoke and struggles to start.
A flakey pressure regulator is certainly possible. Here are a couple other possibilities:

XJ6 Series - EFI Rich Mixture


If the black smoke/rich mixture seems to occur only when the engine is cold, consider the 'cap mod'...

XJ 6 Series III 4.2 - Cold Start EFI Overfuelling


What is every thoughts on the fuel cooler on the aircon. We have had the whole aircon replaced and found out today that they did not add back the cooler.
Over the years I've noticed that the majority of experiences mirror what Grant has said: don't have it, don't seem to need it, nothing bad has happened without it


Cheers
DD
 
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Old 06-26-2014, 04:29 AM
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Found the problem just by accident, checking all the sensors. And found that the two wires leading in to the temp sensor where just pushed into the plug. Grab the plug from the spare and temp hooked the wires up. Problem solved. Whoop whoop, on to the next thing. Thanks guys for all your input. As for the cooler I won't stress now if others have had no issues.
 
 
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