I have a 1988 XJS. I have 2 main issues with it. first, it starts great when the engine is cold, but once it warms up, it takes up to 4 or 5 seconds to start up. And second, Once running, if the temp isnīt at least half way up, when I press the gas too fast, the engine stalls and I have to let it go slowly until I find the point where I can slowly rev it up again. Sometimes even when warm, Iīll press the gas a bit fast (like to pass another car) and it wonīt stall, but it will take a few seconds for the revs to start catching up. What could there problems be?
Iīve already changed injectors, injector connectors, fuel pump, vac regulator, dump valve, Lucas electronic ignition assistance module, speed control module, vacuum hoses and filters. Also cheched the timing and it seems ok. Itīs been improving with every part weīve changed, but my mechanic is stumped now and canīt find the cause of this.
Any help would be greatly appreciated.

 

This might be kind of dumb, but you've changed a lot of parts that could be the culprit without any luck. Could it just be carbon build up? Have you read the section of Kirby's book about the Italian Tune Up? Read his book, but basically really run it hard a few cycles and see if that "cleans it out".

As for starting hard after warm up, there was a thread here a while ago with some causes. A jag mechanic recently told me it was due to ethanol in the fuel now days. My car didn't do it, but he warned me if it did not to worry too much and that was likely the cause.

 

Have you tried pressing the throttle part way while cranking? This is contrary to conventional wisdom with respect to starting a fuel injected engine but it's specifically called out in the owner's manual.

Worth a try?





Could be a fuel delivery problem, quite possibly a clogged screen in the fuel 'sump tank'....the small fuel tank that feeds the fuel pump. It's a pretty common problem.

Might also be a dead spot in the throttle position sensor. This is easily checked with a volt meter.

Details in the archives, or just shout back

Cheers
DD

 

OK, reading a few times what you have done.

I see NO fuel filter replacement??

This may be causing issues, and I say MAYBE.

The TPS (Throttle Position Sensor), under the central capstan is a known issue with these same complaints. Old age is simply getting to them now.

Fuel tank venting is also a concern. Go for a run with the fuel cap OFF, and note if anything alters.

Yes, Ethanol fuel can cause issues in some markets.

Dirty throttle body bores also cause hot start issues, and odd/rough idle.

The CTS (Coolant Temp Sensor), located on the rear section of the LH thermostat housing is a well known concern, as is the wiring to it.

You have 2 ignition coils, one in the "V", and one out the front on the LH side, so a test of spark quality would be a very good idea. You a looking for a FAT "crack" of a spark, Blue is colour. Do the test when cold, and again when hot, as heat does degrade the spark quality significantly, as does old age.

 

OOPS.

Didn't see Dougs post, oh well some repeats do no harm.

 

honduras?? Do you use your AC?? Fuel may be getting overheated causing the starting issue

 

Thanks a lot for the responses. Iīll try as much of that as possible this week and Iīll post results.
P.S. Sidescrollin, Yes Honduras, Yes I constantly use my A/C. How can I determine if fuel is overheating and if so how can it be corrected.

 

Nice. Honduras. I was just down in your neck of the woods. I used to go and work in San Pedro Sula, but this time I was relaxing on Roatan. And when down there I was wondering if there were any XJS' down there

 

As far as I know, at least in Tegucigalpa, I know of only 4 XJS. One Gray (silver?) and one green 88 Convertibles, 1 brownish 87 coupe and my red 88 convertible, out of which I believe only mine rolls around the streets, the others are mostly parked and forgotten.