I inherited a 1983 XJ6 via a passing in the family. I have been pulling wrenched for 35 years. This is a very beautiful car, but does not run correct. Has the 4L straight 6 engine. Idles fine but will not pick up RPM's and hesitates. Once you get it up past 1500 RPM it picks it up fine. You break torque it and it hesitates and stumbles like the ignition system is breaking down. I'm going to list what was done to the car before i got it and what i have done to it.

New Fuel Pump & Filter
Siphon out old gas and replaced with new
new plugs, wires, coil, cap, rotor, Dist pickup, & Module
Reman Mass Air Flow Box

I used a LP bottle with a hose to check for a vacuum leak. None found so far. I dropped the exhaust at the manifold thinking the Cat was plug and ran it with the same performance results.

I would like to get this running correct and sell it. I would appreciate and advise on what I should focus on next.
I'm going to apologize now as I did search the fourms and have not found my answer it I happen to have missed it.

Thanks Sloanie

 

that all sounds like fuel pump, hot wire the pump so you know its getting a good feed. syphoning the tanks is not cleaning them, they may be full of crap starving the flow. new fuel pump may be faulty.
I had all the same problems that was fixed with a new pump. also check fuel line solinoids to make sure they are working and letting the fuel move correctly

 

Hooter, Thanks for the advise. I should have said I did hot wire the pump and even unhooked the fuel line after the filter and wired the pump to drain the old fuel. The fuel delivery from the tank through the pump and filters appears to be fine.
Last evening I played with the distributor timing as this does have an affect. With the vacuum advance unhooked I set the timing and it sounded great. Once I hooked the advance up it still ran good but then started breaking down again. I took the cap and rotor off and hooked my hand held vacuum pump to the advance and pumped it up just to make sure the advance was working correctly and not binding or hanging up.
Now, I am wondering, even thought the plugs have been changed by my uncle and since they are sooty black if I should change them. I wish I still had my Allen oscilloscope.

 

it may also be worth checking your injectors are spraying and not squirting?

 

Hootet, Thanks. I will have a look at the injectors.

 

I would change them or at least clean them. You sound like the type of guy who still has a spark plug cleaner clamped to the end of his workbench . I remember the days when cleaning plugs was S.O.P.

Anyhow......

If the plugs are become blackened again, consider this:
XJ6 Series - EFI Rich Mixture

And just for the heck of it double check that the ducting between the air flow meter and the throttle body is secure and leak free. Odd things happen when it isn't

An incorrect coil can cause weird symptoms as well. You need a coil with about .8 - 1.0 ohm primary resistance. Some parts vendors listings are incorrect and wrong coils are sold.

Cheers
DD

 

Yowee, I've one of those clamped 'temporarily' to my mobile brush/bash
stand. Not a real original, but a mere replica. Kinda reminsiscent (sp) of my old college days in the "full service station".


Nowadays, I use it when my yard engines fuss about starting:


1. Craftsman 4 cycle Honda powered SP lawn mower.
2. Ancient 4 cycle Lauson powered Rotohoe. A light duty rototill.
3. Middle aged 4 cycle Briggs & Stratton powered Lawn vacuum.
4. Decade of so old, two cycle Toro leaf blower.
5. Decade or so old 2 cycle Weed Eater.
6. Predator 4 cycle "Honda knock off" powered old Troy bilt shredder.
7. HF sourced 2 cycle power generator. Anti- hot spell black out duty!!
8. WWII vintage 4 cycle Tecumseh power power generator. Has run, but awaits a fix. Old style rope pull dangerous to males!!!


The two cycles tend to run best dirty, and deposits come often.


Son thinks it a danger to the health of any engine. Some sand will remain and mess up an engine.


Naah,. use the air gun and blow them clean before installation.


Ancient tech to "clean an oil fouled plug". Add a bit of fuel and light it up!! Done that, decades ago...


Carl

 

Doug, Appreciate the advise. Yes, I have a spark plug cleaner. I built and flew a Vans RV-6A & RV3B so I cleaned the plugs during the biannual. The plugs are sooty black and it would not hurt to clean them and gap them. Last evening I had the same thought about the air inlet boot from the new Reman MAF I installed and removed it and reinstalled it to assure it was on correct and no leaks. It all look good and went back together good. Thanks for the link. I was looking for these details earlier. I'm old school and new to the forums and still getting use to the search. Thanks Again.

 

I do have one more question. I have looked all over for a EGR valve and do not see one. Best I can tell from my research they didn't us EGR until the 90's. Is that correct?

 

Right, the USA-spec Series III XJ6 did not use an EGR.


Cheers
DD

 

OK, so over the week end I cleaned and gap the spark plugs. No Luck. Because it still seem to be running rich I changed the coolant temp sensor that controls the ECU. 3rd sensor back. No Luck.

One thing I have noticed is when I take the RPM's up to 2500 and drop it in gear it runs like a rape ape (Great). When I am setting at idle and drop it in gear and start pressing the throttle it starts bucking and snorting. I can make this better and worse by moving the distributor timing. I can never get it all out.

I have been struggling with the thought of the injectors causing this? But if need be I will pull them. Thanks for everyone patience. Sloanie

 

Many of the performance issues encountered with later 4.2 litre XK engine performance can be traced to the Lucas/Bosch L-Jetronic air flow meter.

Here is a link to an article by Roger Bywater of AJ6 Engineering in England:

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

Refer to page 3 regarding problems with the air flow meter.

 

NBCat, very interesting information Thanks! I was hoping since I installed a re-manufactured air flow meter and it didn't change a thing that that may not have been the issue.... I did make some notes to take back out to the shop and check. The throttle switch has me puzzled. I took it off and removed the cover. There seem to be two sets of contacts. Mine was all covered in fluid so I cleaned it in mineral spirits and dried it off. The next day I checked the contacts with an Ohm meter and it seem all good so I put it back on. No change in the way it runs. I don't quit understand the audible sound that your suppose to hear or how to adjust. Thanks again Sloanie

 

Other areas to check for unmetered air entering the engine and causing a lean condition is at the oil dipstick tube. The seal on the dipstick can perish and allow additional air to enter; especially at idle.

Another area I have encountered that can cause erratic performance with the later XK engines is excessive runout in the distributor shaft, which effectively changes the pickup gap at various RPMs.

 

NBCat Thanks once again. I had no idea the dipstick seal would have an effect. I agree on the distributor shaft. I have been thinking of pulling the distributor and going through it. I have to travel for work the next couple days and will have to deal with it when I return.

Funny, I travel for a Large Diesel Engine Company trouble shooting engines and this Jag is kicking my behind....

 

It happens to the best of us, the behind kicking....


I don't get what air into the sump at the dip stick would have to do with engine performance. It might be messy, but oughta run just fine sans the dip stick. Although, the engine has a filtered means of removing crankcase fumes and burning them.


Yes, loose distributor bushings and wobble do odd things, none good.
Been there on several critters...


Keep plugging, it will come...


Carl

 

Additional air entering through the breather system cannot be compensated for by the air flow meter, thus leading to a leaner mixture. This becomes more apparent at idle by causing intermittent misfires.

 

Guys, Thanks for the encouragement. This engine idles fine and runs fine at high RPM. Getting from idle to high RPM is when it hesitates and stumbles. Again, will not pull load if you brake torque.

I plan to pull the distributor. Question: there is no pump shaft or anything that can fall off and into the pan correct? I plan to mark the rotor and pull it and then put it back in the same location not disturbing the engine rotation while it is removed.

 

The oil pump runs off the lower part of the shaft and the design of the distributor and shaft allows the distributor to be installed in only one position.

 

Perfect Thanks NBCat.