Hello People,...Series 3 car was stored indoors almost 20 years. Has about 43,000 miles on it. Idles rough, occasional intake back fire when accelerating, and has generally poor performance and does not smoke.
Replaced so far:

• All injectors (including cold start)
• thermostat (runs @ 85c)
• Plugs, wires
• air filter
• fuel pump and filter(twice)
• fuel tank screens
• thermotime switch
• coil
• ignition module
• air intake bellows hose and related
• Numerous other stuff unrelated to performance

Performance and idle settings info after warm-up:

• 700-750 RPM in "Drive" is rery rough
• 950-1000 RPM in "Park" sort of rough
• 18-19* BTDC vac hose plugged
• 25* BTDC vac hose connected
• Plugs amber colored electrodes set at .035"
• 140-145 PSI on all cyls after 3 revolutions
• 16-17" vacuum @ manifold
• Throttle body flap gap set at .002"
• Idle speed adj. screw completely bottomed out to lower RPM.

Also note... Smog/Air pump, etc. has been removed, vac line plugged @ manifold, and head ports plugged. Fuel tanks have been "in-car" flushed twice(Very rusty).

Next to do:

• ??????????

Thanks, Jim

 

I'll toss out some random ideas

- Carbon tacking on the inside of the distributor cap causing a misfire? Visually inspect.

- Fault with injector harness causing one or more injectors to not fire consistantly? Use a mechanic's stethoscope to listen for even clicking from each injector.

- Excessively lean mixture at idle. Any sign of someone altering the AFM mixture adjustment screw? (There's a plug that must be removed....they might've left some witness marks)

- Ground wires at rear of water rail clean and tight? These are the fuel injection grounds

- All wiring at the coil in good shape?


Cheers
DD

 

Thanks Doug,
I'm hearing allot about vacuum. Is the 16-17" enough to eliminate that possible problem?

Coil wires look clean and secure, as do the injection ground wires.
Injectors sound steady.
Mixture screw had no plug over it. With engine warmed up, in Park, at about 1000 rpm, as low as I can get it, I turned the mixture screw in almost 3 1/2 turns until it bottomed out. No change in rpm or steadiness. Turned it CCW 4 turns with no change.

Haven't got to the distributor yet.

By the way,.... Something I keep failing to mention. I have a noise in the front area of the motor that sounds like a few small rocks rattling inside an empty beer can. At first I thought fan clutch, but doesn't appear so.

Thoughts???

 

oops

 

More suggestions.......

- Engine earthing strap, down near the bellhousing
- Vacuum line for heater valve
- Vacuum line for brake servo
- Air flow meter (a difficult one as only swapping with a known unit can show a fault)

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

 

Not sure if I understand the question but 16-17" isn't especially bad. We'd like to see something more like 18-20" at idle with a sweet running engine but you're not that far off.




I forgot to mention (although you may already know) that any adjustments here have to be made slowly. It take a few moments for the engine to respond.

But.....

Since you noticed no change of any kind it's probably because a bigger problem is masking the results of the adjustment. This mixture adjustment is just air bleed or 'bypass'. I think you have another air bleed elsewhere that bigger then the range of adjustment of the mixture screw. The 1000 rpm idle tends to confirm that notion.

Have we talked about the Aux Air Valve?







Which reminds me. Try backing down the timing just a wee bit. The spec is 17ºBTDC. You're a bit high. Probably insignificant....but ? It may help bring your idle speed down if nothing else.




Water pump/alternator/air injection pump bearing?

Might be a loose timing chain as well. A slightly loose chain with rattle make noise as you describe. Typically it goes away or is reduced when the engine is hot. Not hard to adjust.

Cheers
DD

 

Hi Guys, Well it's been a long day,....
Distributor cap and rotor looked clean and fresh.
All the vac hoses/lines I can see and trace look good and secure. I've yet to tackle the AAV and related lines under the manifold.
Is there a normal pre-set for the idle speed and air mix screws. The speed screw increases RPM as I back it off, so I left it bottomed out. As mentioned, the mix screw makes no change at all.

I appreciate your time and advice. I've been learning a great deal.

Thanks again, Jim