my xj is smoking :(

I have a 1993 xj, it smokes a bit when i start up and then continues to lightly smoke. what do i need to do to get it to stop. It has 167000 easy miles on it.

What colour is the smoke?
Does the engine run well or does it run poorly?

Black smoke = rich-running engine -> bad O2 sensor, bad CTS, bad IAT, plugged cat
Blue smoke = burning oil -> worn rings or valve stem oil seals
White smoke = steam -> leaking head gasket, cracked head, cracked block

my xj is smoking

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You could send it for a course of acupuncture to help it quit.

is the smoking coming out the tailpipe or from the engine compartment?

the smoke is black but its not a heavy smoke. and its only coming from the exhaust.

creed4017 said:

the smoke is black but its not a heavy smoke. and its only coming from the exhaust.

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Ok, that narrows it down to the following:
Black smoke = rich-running engine -> bad O2 sensor, bad CTS, bad IAT, plugged cat, vacuum leak, bad fuel pressure regulator, thermostat stuck open.

Check for each of these items. There's a 99% chance that your problem is one of them:

1. O2 sensor. If the output from the signal wire is stuck near 0.0v and there's black smoke coming from the tailpipe (ultra rich), the sensor is falsely telling the engine's computer that the engine's running lean so it adds more fuel when it isn't needed.

2. Vacuum leak. Check the intake manifold vacuum at idle. It should be at least 16"Hg. If it's much less than that, look for leaks.

3. FPR. Check the fuel pressure at the injector rail. It should be 30-31psi with vacuum connected and 39-40psi with vacuum detached.

4. Plugged cat. While the engine's idling, partially block the tailpipe with a potato or something similar. If the cat's OK, the increased backpressure will cause the engine to struggle, backfire, or even stall. Bang on the cat with your fist (only when it's cold!). If it sounds like marbles rattling in a can, replace it.

5. If the resistance across either the IAT or the CTS is infinity, the engine's computer will think that the engine's cold and it'll run rich (akin to a carbed engine's choke being stuck closed).

6. A thermostat that is stuck open will cause the engine to run too cool. The engine's computer thinks that the engine's still warming up and it runs the engine in "choke" mode. Start the engine from cold and let it idle. Keep your hand on the upper radiator hose. When the t'stat opens, the hose will suddenly harden and become hot. Check the coolant temp. gauge at that point and see what it reads. It should be at about 3/8 if you have the OEM 195* t'stat. If it's at 1/4 or less, change the t'stat.

thanks ill start checking this afternoon

Check engine light on? Maybe try pulling codes.

Mike

MDMIKE said:

Check engine light on? Maybe try pulling codes.
Mike

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Good idea. Even if the CEL doesn't come on, nos. 1 and 5 on my list should trigger a fault code that's stored in the PCM.