Rough Start

[SilverXJ]

I have a rough cold start issue on my 4.6 stroker, 2000 XJ. Occasionally it gets so bad that it throws a mis fire code. All other times it is fine except idle where there is a ever so slight misfire, not enough to throw a code, but you can hear it a bit. I am running NGK plugs, one or two heat ranges colder than stock IIRC, ZFR6F11 gapped to .040". I also have the stock injectors, but it runs a good AFR at WOT. Its only for the first 30 seconds of start up or so. The rough start doesn't bother me. What does is the engine light by the mis fire. Any ideas?

[Flash]

Put a fuel pressure gauge on it and see if fuel pressure bleed off after you turn it off for 10 minutes

If the pressure drops more then 5 psi......you might have a leaking injector that dribbled down to the intake valve and puddles on the piston when started...........

My be too cold of a plug

Injector o-ring sucking air when cold

Flash

[SilverXJ]

Could be injectors, could be plugs, could be the coil rail. So far I have only noticed it on cylinder #2, the mis fire that is. Can't if that is the only cylinder that starts rough or not. If it is a injector bleeding down, wouldn't it take a few cranks to build fuel pressure?

[Flash]

Could be injectors, could be plugs, could be the coil rail. So far I have only noticed it on cylinder #2, the mis fire that is. Can't if that is the only cylinder that starts rough or not. If it is a injector bleeding down, wouldn't it take a few cranks to build fuel pressure?

Not necessarily, the fuel pump will cycle on for several sec.when you turn the key on.

You could also get some spair o-ring, in case you cut one removing it, and swap injector, and see of it changes with cylinder set the misfire code.

Sense it is only on cylinder setting the miss fire, remove the plug and check for a cracked poclein.............Could even be a spark plug wire that is shorting out when cold.

[Flash]

SilverXJ,
When it sets a miss fire code(check eng light come on).......is it sylinder #3? And does it make/ have this same problem when shut off for ten minutes or so, after you have run it for a will and shut it down?


Flash

[SilverXJ]

No, this isn't the TSB issue. I've had it twice so far on cylinder #2. It has only thrown a code twice. I have the heat shield TSB for the hot start and the PCM programing for the cold start. On the previous engine the cold start issue was fixed by the reprogram. This is something different.