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Luke
Dodge Dakota
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6/13/2006
21:16:15

Subject: White smoke and rough idle.
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My Dakota is a 1993 4X4 Club Cab 3.9L. When starting the
engine cold, there is a puff of white smoke that comes out of the
exhaust. Also, it runs rough for about 30-45 seconds. After
that it smooths out. Power doesn't seem abundant lately either.
It has had new intake gaskets and new timing chain/gears/
tensioner.

A friend suggested that maybe it needs an O2 sensor because it
may be running way too rich from a bad sensor. Anyone had a
similar problem? It was using a bit of coolant before the new
intake gaskets and he said that has a tendency to ruin O2
sensors.

It burns no oil and doesn't lose any coolant so the white smoke
has to be gas from being a bit flooded.

Anyone have any ideas?



screwuphead
Dodge Dakota
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6/13/2006
21:30:48

RE: White smoke and rough idle.
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My friend had this problem of a "misfiring" in his BMW, we changed the coil, got new plugs and wires, yet it still "misfired" so i suggested the CO2 sesnor, fixed everything. So if it seems to be mis firing, it could be possible.



bludak
Dodge Dakota
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6/13/2006
22:47:07

RE: White smoke and rough idle.
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From my experience, white smoke means you are burning coolant. Maybe a head gasket problem. Never seen white smoke from a fuel problem.



Obio3
Dodge Dakota
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6/14/2006
01:35:43

RE: White smoke and rough idle.
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bludak is correct. White is always coolant. You said it does this after sitting all night. But you see nothing otherwise. this tells me it's a rather small leak. Don't forget, you have a reservor so it may be low by now but radiator still full.

So many problems .... So little time



Huggins
Dodge Dakota
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6/14/2006
21:56:20

RE: White smoke and rough idle.
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If it is coolant, a leak this small is going to be fairly hard to find... The best way I know to do a hunt down to this degree is to use some fairly hard to find tools unless you just so happen to know someone who has them or have them yourself... Keep in mind that just because it looks full doesn't always mean that it is... The two tools that you need to use are a boroscope "the hard one to find" and a radiator leak tester "it allows you to pressurize the entire cooling system"... What you will have to do is get the truck up to regular operating temp, while the engine is running remove the radiator cap "so you don't have the boiling presure spike if you had cut the truck off" and install the pressure pump "radiator tester", now cut the truck off and remove all spark plugs, pressurize the cooling system to a higher than regular spec "20-30 psi" and you now should be able to run the boroscope down each plug hole and look for any coolant seapage... If none is found leave it presurized and check back on it every 30 minutes or hour... Some leaks require very specific temps before they will leak or bypass the gasket, which may be exactly what you've got... These engines are kinda known to crack inbetween the intake and exhaust valve seats and leak coolant out through there, so you'll have to twist the boroscope around and look everywhere that you possibly can for the leak... Make sure to use a boroscope with a light on the end of it so you'll be able to see in the combustion chamber...

I also noticed that you had done some engine work on it, didn't use some cheapo gasket maker on it did you??? It's just that some of the gasket makers contain agents that will destroy o2 sensors... The agents get into the combustion chambers via pcv and crankcase breathing apparatus's then move on to coat and destroy the o2's... BUT ussually when this happens the truck when run great for about 15-20 minutes after the repair then just absolutely misfire and run like junk, so it doesn't sound too much like this... Atleast not 100% anyway from what you had said... Could still be going bad from age and causing your symptoms, so you can't ellimenate them just because you didn't use a sealer as your friend pointed out...





cuzindoug
GenIII
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6/15/2006
00:07:11

RE: White smoke and rough idle.
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Yeah, what he said, also, the O2 sensors don't "kick in" until after the vehicle reachs operating temperature.

If it doesn't fit, force it. If it breaks...well...it needed to be replaced anyway.

Huggins
Dodge Dakota
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6/15/2006
22:36:23

RE: White smoke and rough idle.
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O2 sensors don't show any output signals for atleast a few seconds on newer vehicles after startup and for a maximum of 5 minutes on older vehicles after start up... The few seconds on the newer vehicles is due to the heaters that they all have built into them now, it allows them to reach an operational level much sooner... The older one's didn't have the heaters built into them which is why it may take up to 5 minutes on the older one's to reach their operating temp or the temp in which they will be able to seperate and rejister the oxygen molecules... You are absolutely correct there... However the fuel curves that are used during cold engine start up are derived from the previous operation of the vehicle... In other words the fuel curve that was set the last time you ran the truck, "when it went into closed loop" is the one it will run on and use during ALL open loop strategies during this next or occuring drive cycle... SO if the o2's were bad and making the engine run "out of the norm" all of the time, then that "out of the norm" fuel curve would be used during the next cold startup...

Hope this helps a little more... Sorry for the long postings...



Luke
Dodge Dakota
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6/19/2006
01:33:25

RE: White smoke and rough idle.
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Thank you all for the responses. They were very helpful. I have
mostly solved the problem. I found that my throttle position
sensor was seriously misadjusted. I had adjusted it and had it
right but must have messed it up when doing some other work.

Anyways, it was making the computer think the throttle was
partially opened when it wasn't. So, it was causing the engine to
run way too rich.

This was somewhat confirmed when a friend and I were messing
with his lawn mower. He pumped the primer 6 or 7 times
instead of 2 or 3 and loaded it up. When he started it, it poofed
out a white cloud just like my Dakota has been doing.

After I adjusted my TPS, the white cloud is almost non-existant.
I do believe it still needs an O2 sensor but it isn't as urgent as I
had believed. I will wait and replace it after the catalytic
converter is taken care of.

Again, thank you all for all the advice. It's most appreciated.



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