Rough idle and white smoke

[Avengingyj]

I have a 1998 TJ, and it has a rough idle ONLY on startup. Rev the engine/give it a little gas a couple times and it smooth right out for the rest of the ride. While it has a rough idle it also has whitish smoke coming out of the tailpipe, but it doesn't smell like a coolant leak. Any ideas?

 

[Chris]

White smoke? Sounds like you’ve got a blown head gasket. Does it blow the white smoke the entire time you’re driving, or just at start up?

 

[K0LCB]

I agree with Chris

 

[Kiwi TJ]

Found this.. Top 4 reasons for white smoke

1. Condensation - especially in cooler climates
2. Coolant leak - may not go away after it warms up
3. Piston ring or valve seal leak - can be blue smoke too
4. Bad fuel injectors - could be a good time to change them out

https://cartreatments.com/petrol-engine-blowing-white-smoke/

 

[06lj]

Coolant will smell sweet and is rather unmistakable. If you are not loosing coolant I would start looking for a misfire. Unburned gas can give you a white'ish exhaust. A good sniff of it will generally burn your eyes a bit.
Do you have any codes?

 

[Ct_tj]

Sounds like a leaky injector, its letting fuel in to the engine after you turn it off. Once it fires up it has to burn/blow out that extra fuel causing the white smoke and rough idle

 

[dbbd1]

Sounds like a leaky injector, its letting fuel in to the engine after you turn it off. Once it fires up it has to burn/blow out that extra fuel causing the white smoke and rough idle

So, the OP may be able to do a fuel pressure check, to see if it bleeds down? (I know this does not guarantee that it is the injector though)

 

[Indy]

Sounds like a leaky injector, its letting fuel in to the engine after you turn it off. Once it fires up it has to burn/blow out that extra fuel causing the white smoke and rough idle

X2. Also check your spark plugs. They can often tell you what's going on in the cylinders.

 

[Ct_tj]

So, the OP may be able to do a fuel pressure check, to see if it bleeds down? (I know this does not guarantee that it is the injector though)

Chances are is it's a slow leak taking a few hours to leak enough to notice on start up. You're going to see some pressure bleed off regardless of the integrity of the fuel system. The best thing is to pull the injectors and set up a rig to bench test them. If the OP has any race shops in the area hopefully they can do it if the OP is not comfortable doing it. The easiest thing however is to just pull the plugs and look at them. If one has a ton of build up on it, that's probably the problem cylinder. A black plug would indicate rich/possible leaking injector. White or grayish chunky buildup would point towards an oil burning issue though

 

[Goatman]

White smoke means water. Black smoke means oil. This was the mantra when I was in college. Sweet smell means coolant. Perhaps you have condensation in the exhaust and the white smoke is a non-issue. The initial stumbling could be some water settles in the fuel tank and is injected at start up. But stumbling (on a carb) meant fuel issue. Normally too much. Not nearly as straight forward with injection and computers. But I would have to agree with the above points about injectors. Perhaps a real strong injector cleaner will fix it, but only if the problem is not severe.