Hi all,

My 1998 XJ8 has been performing very well until the snow and cold arrived!!
When left out during the day I have trouble starting her. She turns over and fires but only revs momentarily to about 800 RPM before dying. Usually after a few attempts I can coax her into going with foot on the floor gas pedal but I am getting worried we might get stranded.
Any ideas which of the usual suspects I should check for?
Thank you,
Michigan.

 

Check these things, your ground terminal in the front of the car, test the alternator (often goes out), and go to an autozone to see if you battery is still good.

 

Try this the next time, turn the key on and count to 10 before you crank to start. See if that helps and let us know.

 

I tried counting to 10 before cranking but that doesn't seem to make any difference..I also switched the fuel pump relay for another but again no great difference.
The engine cranks as normal and fires as it used to but it only revs to about 400 then dies, same next time. I am getting better at trying to use the gas pedal and pumping to "catch" it just right with the gas pedal near the floor to get it to stop from dying!!
Thanks,
Michigan.

 

Do you have a check engine light or any warnings or OBD codes?

 

No check engine lights, I should add that once warm the engine will restart after I've driven it a bit just fine, but when I park up at work and it gets cold for half a day (remember it's below freezing here outside all this month) the same starting problem occurs.

 

When were the plugs replaced, TB cleaned, MAFS cleaned and the filter replaced? I would also check that the breather stub is open and clear. If they have all been done recently I would be looking at a fuel additive like BG 44k. This activity sounds like a fuel presentation problem and all the above should help.

 

I know the spark plugs are new and have just replaced the battery. No joy, still fires but doesn't start when cold. Looking at the JTIS disc I'm thinking ECT sensor, any simple tests or as it is an inverse resistance sensor can I disconnect it before start up and reconnect it after start up or is that just a VERY STUPID IDEA?
The car is garaged but it has been very cold outide (-20C last night) and the JTIS disc suggests that the ECT sensor keeps the injectors on sightly longer for a cold start and this sounds logical, I thought it might be something to do with the choke cycle but any ideas are greatly appreciated, as ever.
Thank you,
Michigan.

 

I looked at your post and listed a few things in an effort to pull it all together. I am not familiar with the procedure you are speaking of so I will refrain from commenting on it for now. Not sure on the next step but will give It more thought I feel it is fuel but what part. I hope others can step in and help.

Recap,
1998 XJ8 performing well until cold weather
When left outside in cold turns over fires up revs momentarily 800rpm then dies.
Can coax car to continue to run with the gas pedal.
Attempted delay start no change.
Switched fuel pump relay no difference.
Now only revs to 400rpm.
After engine runs for a while it will restart normally Note; engine hard to start after cool down.
No engine light and no OBD codes.
Plugs are good, battery replaced

 

Hi Mich,

I hope I can offer a baseline and maybe you can spot an easy difference.

I'm in Novi, MI and my XJ8 sits outside full time. This morning it says 9 degrees F on my thermometer outside and while mine cranked slower than in the summer it still lit off after about 5 seconds. Once started the engine came up to a base idle of 1100 rpm on the tach right away. After it warmed up to operating temp the Idle dropped to around 700.

Assuming your car is not belching black smoke it's likely you are to lean when it's really cold. Sounds like you might be onto something with the sensor.

Here's what I know about my car:

144K on the odometer.

No mods to the drivetrain.

Engine is original. Only internal work is tensioners and chains.

10w-30 oil. (I'd prefer to use a 0W-20 Amsoil synthetic but the VVTs are noisy when I do)

On super cold starts like today I make sure the Auto Head Lamps are off and the Heater Blower Motor is off to minimize load on the battery.

Battery is 1 year old.

I run Premium fuel all year long. I almost always buy from a major brand. BP is in the car now. I don't dump in any additives.

Hope this helps a little.

Ken

 

I replaced the battery and the ect sensor and had to do an extended cylinder wash start procedure as the engine was flooded. Managed to get it finally going after about an hour and left it to warm up.
It now runs very very rich and doesn't lean out. I am afraid to take her on the road to a mechanic shop.
What should I now be looking for assuming that I can restart her and she again just runs (idles) rich.
Thanks to all for advice so far.
Michigan.

 

What makes you think it is running rich and do you have any codes?

 

I don now have a check engine light but can't read the codes myself, at this stage I want to get it running to get it to a mechanic (!).
The exhaust smells very rich after I let it warm up and runs rough when revving it.

 

What is a cylinder wash start procedure? My Jag wouldn't start today, and I'm going to work on it in a couple hours. It seemed to fire norally, but I let go of the key a split second too erly and it died. Subsequent attempts sounded strange, like a weak battery.

Thanks

 

I have a happy ending to report!!
Having replaced the battery and the Engine Coolant Temperature Sensor (My JTIS disc gave it as a reason for firing but not starting when engine cold, which was my problem) I then flooded the engine trying to start it.
Last night I did the cylinder wash procedure as listed on this web site, took for ever, but stuck with it.
When the engine did start I left it running in the garage with the door open, but I think the exhaust build up in the garage must have affected something as the engine seemed to run richer and richer, I was scared to even take her around the block for fear of breakdown. Engine warning light was on and so I feared the worse...ie towing to a mechanic.
Today I came home from work and decided to take out the new ECT sensor to measure the resistance against the old one in case I had been sold a dud and was ready to trade the car for a golf cart or something reliable when I thought I'll just see if she starts before beginning a total strip down.
Well she fired first time, (in the cold) and immediately settled to proper idle. I took her around the block, no problems and decided to risk it to Autozone to have the codes read and cleared. Well after a few starting cycles at stores on the way the check engine light went out (I imagine the sensors readjusted themselves) and we are back to perfect starting again!!
So; the ECT sensor must have broken or gone out of range so the engine began to fire but not start in the cold, I managed to start it using the throttle to 'catch' the revs just right a few times but the 13 year old battery (original) struggled. New battery helped but last Saturday I failed to catch the revs and must have flooded it with the known problem with that engine..cylinder wash.
When I did manage to restart it the fume build up in the garage threw every sensor astray but once cleared today it seems to be fine again, I should have pulled it out into the open air. The ECT sensor was the original problem which was solved for $14 the rest was circumstances.
For those of you reading this in the warm, last Sunday morning it was -8F or -22C !!! and even though garaged, (not heated though) the cars need that extra fuel injector time on start up, as do I at those temps.
Thanks to all for the advice, fantastic as ever.
Michigan.

 

I am so pleased that you got it running and that you found the problem. I must tell you that I was not sure that the ECT was the problem, you proved me wrong. Good Job!

 

the new replacement of the sensor more likely threw off the fuel trims tremendously at first startup. After several engine runs, the trims self-adjusted, and those error codes (reduced performance perhaps?) were probably from too lean/rich conditions...whatever it was, and do turn themselves off when self-corrected. When making a huge fuel/air/spark change such as what you did, I recommend a hard reboot with the battery to clear the adapted engine management curves, and start from scratch. You got that way, though just took longer than necessary.

 

where exactly is the ECT sensor located on our cars? is that the same as the intake air sensor? i've been searching JTIS for the ECT location and have had no luck...

 

Here's where mine is, the brass coloured thing just beside the bulgy looking hose.

 

This is showing the same thing.