Ok, new 1988 XJS owner. Car ran fine when I picked it up and drove home. Started it a couple days later and it would only start with heavy throttle opening and then just run at 1200 rpm very roughly and smoke (black I believe) heavily.
After running for a couple minutes the exhaust was making the popping noises as it cooled; strange for just a short running time. Any ideas?

 

Mmmm, you are new, welcome to our side.

OK, an '88 is Lucas ignition, good at the moment.

A few things come to mind, so basics first, it usually sorts them and costs near nothing.

The CTS (coolant temp sensor), which is located in the rearward section of the LH thermostat base. It has a plug on top the SAME as the injectors, and is well known for overfuelling. The 2 wires inside that plug also can cause issues.

The FPR's (fuel pressure regulators), of which you have 2, also fail, and raw fuel is drawn inside the engine, and overfuels badly, usually stalling eventually. Remove the small vac hose from each and observe fuel presence, or fuel odours. The lack of fuel, or odours does not give them a 100% pass, but is a quicky test. Old age is not being freindly to them now.

The catalytic convertors are possibly the crackling you hear, as they have ingested huge amounts of fuel, and possibly came very close to catching fire.

 

i have a pair of newish FPRs for sale, as well as catless downpipes

 

Thanks Grant, you nailed it. The CTS was unplugged. Neither of the FPRs had any fuel or gas odor. Reconnected the CTS and it fired up and ran fairly well. I'm sure there are many maintenance items to get to on this car to make it a reliable driver.
Thanks so much for your help. It is very much appreciated!
Don

 

Hmmmm...wonder what shipping would cost on those...

 

Bloody good fix.

Told ya, simple cars, with simple problems.

ENJOY

 

You seem to have a lot of experience with the XJS. I'm wondering why a 5.3 liter V12 with 11.5 compression is only making 262hp and if giving it a real exhaust system, say 2.5 inch with single good flowing mufflers on each side would release some power?
That it makes that 262 hp at 5000 rpm yet has a 6500 rpm red line seems to point to the car being choked down......

 

Yep.

We run 12.5:1 comp on the HE in our market.

The USA cars were detuned, that has been going on for decades.

Ours make 300HP as is. The cats dont help, the smallish exhaust dont help, the pollution rubbish chokes the hell out of it. We missed a lot of that stuff until about '89.

My V12's (PreHE and HE) all have:

2.25" exhaust all the way, with sports type mufflers.
NO AAV on the rear of LH head.
NO balance pipe.
NO over run valves.
71mm throttle discs.
Foam air filter elements (home made).
Cold air intakes, right down the front under the bumper.
Vac advance ONLY on the distributor, as versus the retard/advance we did have.
Thermo fans (Ford), and 1 "V" section cut off the front pulley (lighter, goes fsater)
Full mechanical FPR, no vac signal.
High energy single coil.

Lots of other little goodies I did in the 16+ years of ownership of the XJ-S.

It goes like stink, cruises effortlessly, and snaps real bad when needed for overtaking on the highway, awesome beast. Economical as well.

 

If I can decipher all that you did I should be able to duplicate it with the exception of the 12.5 compression as I'm stuck with 11.5 cr. Some pics of the cold air intake would help. Along with details on your various mods. Thanks!

 

OK, I have many papers of what I have done over the years.

I tried to send you a PM to get your email address so I can send them to you, not allowed, maybe due to your newness???.

Some are BIG, so I trust your IP mob have the goodies to accept them, some do not.

So let me know your email details and I will sort and send all the relevant papers I have.

 

please send to will33382005@yahoo.com and thanks!!

 

probably more than my asking price on the pipes. lol