stick with 87 octane, it will not improve anything to use a higher octane, (it will however, improve the amount of money in the gasoline seller's pocket :-)

the 4.2 engine was designed to run fine on 87 octane.

sounds like a bad Cold Start Injector, I hope a new one fixes the problem.

 

Drove 90 miles there and back yesterday, and she was lovely to drive. Same cold start problem, only a slightly lumpy idle though 700rpm in D with my foot on the brake at a red light, and 1000 if I shift to N even if very hot. A new CSI is in the mail to me. Probably a Pertronix distributor and coil plus new leads after that.

 

Good work on nailing the CSI.

I really hope you could check your fuel pressure regulator like Doug mentioned a few weeks back. On my friends 77 XJ12 I have been working on (ohh - over a year now), I went through myriad tests for isolating the lumpy, stinky idle - lights off looking for arcing, pulling injector/spark-plug leads, dialing in the throttle linkage with feeler gauges, etc.

Finally put a fuel pressure gauge on at the cold start valve hoses (not sure how you would tap in on your newer car) and one of the two regulators was flapping in the breeze as to pressure readings. I mean flapping, like 20-40psi six times a second.

Grant told me to try to clean the bad one out. I did, but bought a new one also. Flapping went down to maybe 5 psi swing with old but idle was soooo much smoother and the vicious rich stink was cut 90%. Looking forward to installing the new one.

Would be a bummer if you fixed your cold start issue and carried on with a tired regulator, if the culprit.

 

Good point, I forgot about that. Or rather, moved it to the back burner because I haven't a clue how to use a fuel pressure gauge. I'll google it now

 

I haven't checked the fuel pressure yet but this suddenly started happening: I pulled out of my driveway, the engine would cut out, then come back, then cut out...and listen to the new sound from my fuel pump.

 

sounds like an ignition cutting out issue more than fuel, check your ignition SWITCH, yes the switch where you put your key in ? if it happens again, inmediately grab and hold the key in the RUN position to see if the cutting out stops.

 

Good thought Jose but my switch is tight (I did try what you suggested). The car has <30,000 miles. Cap and rotor look new (the car had been used very very little for several years then had $4K+ spent on reconditioning it to pass a safety inspection)(not by me ). LOTS of parts are one year old. Except the spark plug wires. They look like the originals to me so I'll replace them. I also have a fuel pressure regulator and fuel filter on the way. Having trouble getting a cold start injector (plenty out there but I have been dithering), but that's a different problem from this cutting in/out thing.

 

I'll just keep updating, in case anyone is interested:

Doug, your hunch was spot on. Bob, I didn't test the pressure but I did replace the fuel pressure regulator. In summary, my car has four problems simultaneously:

1. black smoke is too much gas says Doug, and that's because one of my spark plug leads at the cap was squashed a bit (the brass end) and didn't fit the cap snugly. Also maybe there's something to the theory of filling up with 91 octane and going for a run to blow out the carbon.
2. cutting in and out, I believe now, was caused by low and/or inconsistent fuel pressure. When I say "cutting out", the engine didn't actually stop running but here's what was happening. I'd blip the throttle and revs would immediately drop by 500 then resume and let me accelerate. Replacing the fuel pressure regulator solved this.
3. Cold start injector or valve (CSI) still doesn't work, mine won't arrive for two weeks, so I will continue to have the cold start problem.
4. My fuel pump now regularly wails like a banshee, and in fact needed a thump to get going the other day. I shall install the new one this weekend.

Once the CSI and new fuel filter go in, I will probably discover other problems, not just these four. That's Jaguarship for you.

Thanks everyone for pitching in or following along. This 1986 Sovereign is a happier car thanks to jaguarforums.com

 

Finale: new cold start injector solved the cold start problem. New spark plug leads solved the missing/rough idle. Probably the old leads contributed to the black smoke issue.

The final remaining "problem" is that the engine still idles at 900-950 hot. The auxilliary air valve is working at least somewhat because it does slow the cold-start high idle after a minute of running. But otherwise, she's running sweet. Thanks to all of you

 

Asking here because it is the closest subject discussion I found . . . I have an 87 XJ6 6 cylinder that I purchased a few months ago. There are 95K miles on it and it is mostly original. I drive it about weekly for fun and to keep it active. I live in Florida where it is warm and sometimes humid and the car was previously driven in Georgia for a few years.

Often when I start the engine I get black spots and some water out of each tailpipe. The black spots are carbon soot and although not that much, they seem to track on my feet and make a mess. Although these spots are not near my largest challenge with the old Jag, I am venturing into trouble with the lovely lady of the house.

Please send along any suggestions? Many thanks!

 

I think you have more of an "internal combustion engine" issue than a "Jaguar" issue. The water (liquid) is just the result of the warm exhaust gases passing through the cool exhaust pipe and condensing the water vapor in the exhaust (just like a "moonshine still"). Normal. If you drive for 15+ minutes at road speed, the exhaust will get hot enough that it will no long condense the vapor into a liquid. It will then exit with the exhaust in it's gaseous form.

The soot drops/spots are most often caused by a rich air/fuel mixture or engine burning oil. If the inside of the tail pipe is black and dry/powdery (that's a technical term, in case you didn't recognize it) it is probably rich mixture. If it's black and tacky/tarry (another one of those) it is probably from burning oil.

Take a look at your spark plugs, are they black and sooty or black and oily? I am assuming your S3 has fuel injection, in which case I can't help you with particular trouble shooting, but there are some very experienced owners on this Forum that can.

Dave

 

You mentioned a fast idle. that could mean a vacum leak. In turn mean a hard cold start. lean mixture..

Carl

 

when I bought my 1984 in 1989, it did that twice. Black exhaust smoke and missing.
I took it to the mechanic (who knew the car), and he told me "that car has been sitting", "take it for a long drive". I did, and after that it never did it again.

 

Not sure if I ever mentioned elsewhere...I had blown the head gasket right where those two sooty spark plugs were.

 

the last couple of days my 86 S3 4.2 has been running great and then missing/stalling, replace coil and swapped over distributor and amp thinking it was ignition, thought all was good and went for 100km drive no worries, next day fine and then turned to crap, let it sit for an hour and then ran sweet again to get me home. start up today running like crap with fuel pouring out my exhaust manifold[also exposing a previously un seen crack leaking out fuel when heat shield was removed], front 3 plugs oily and rear 3 sooted up, cleaned plugs and all have a good spark when engine running. Any ideas where to start on the over fuelling?

 

Over fueling in general:
XJ6 Series - EFI Rich Mixture


This pertains to over fueling when cold but is a worthwhile mod on GP:
XJ 6 Series III 4.2 - Cold Start EFI Overfuelling

Cheers
DD