Ill try to be brief as I describe my issue, but it'll be hard. About a month ago I was pulling my horse trailer with this truck & went into town it ran fine until I shut it off and started out again when it started to act like it was missing. By the time I made it home with it it was running really rough and hesitating. I'm getting a grey smoke but there is a black fluid coming out of the exhaust (oil?) There is an intermittent sucking sound at the AIC part of the throttle body. It misses and runs rough through out the throttle range. I have no current codes and have changed AIC, TPS (did have a code for it at one point) and upstream O2 sensor and have pull and cleaned the throttle body and replaced gasket. The exhaust smoke smells of fuel but is more white or grey than blue. I'm not seeing any loss of coolant so I don't expect it is a head gasket, and I don't see any oil use at all. When you rev it it will still miss but with backfire, sometimes through the exhaust and sometimes out of the TB. It has 185,xxx on it and I am at a loss as to what to try next. I have searched the forums and the web in general and can't seem to find anyone with the same symptoms I have. Any ideas?

thanks,

 

How long since the sensors were replaced and did you remove negative lead on battery before replacing? PCM may not have learned all the new sensors yet.
Try a full tune up....plugs, wires, cap n rotor. New ignition coil while your at it.
Back fire is from valves being open/ closed out of sync when spark ignites.
I've had sooty water come out the exhaust on my 99 with high miles. Carbon residue and normal condensate. But mine was burning a lot of oil also.

 

New plugs and wires, new cap, haven't replace coil yet. This was done after problem started about a month ago. I only changed the upstream O2 sensor but have unplugged the other one and no change. Battery was disconnected during change ( I even pulled the plugs on the PCM to check for corrision or bad connection. The whole no codes thing is really annoying, my scanner does live data and I don't see anything to much a miss, but then again I don't know if I'd know or not. I ran some Blue Devil through it to see if anything changed, and the only thing that did was there was enough water left in it and it got cold enough that I popped a freeze plug, but with that back in there was no change. I always thought that backfiring in the exhaust and in the TB were caused by different things. I have head gaskets in my garage because everyone keep telling me the white/grey smoke is coolant, but it just doesn't add up. How could a head gasket cause a backfire in the TB? I could see in the exhaust if enough water were getting in the cylinder to keep fuel from igniting and then it fires in Cat or muffler, but not the TB. I just dont want to tear into the heads to find it's something I am missing.


Maybe someone can explain how the throttle body actually works. It appears as though the throttle (acc ped) only controls air flow. Does the pulse width of the injectors firing change as acceleration occurs? I ask because as I was troubleshooting I had my daughter turn key on to check voltage on a sensor while I had the TB off and she accidentally cranked it and it fired and went full throttle. It didn't seem to smoke or sputter then though she shut it down in a hurry, but that also lead me away from a head gasket, because if it was that I should have had smoke/sputtering then, right?

 

Yes, pedal controls air flow via TB, and TPS sends throttle position signal to ECM, which then controls injectors.

 

Time for a compression check, or better yet, cylinder leakdown test. See what the numbers look like.

As it started all at once though, I would almost suspect cam, or crank sensor..... cam sensor controls when, and which, injector fires. That being bad would explain some of your symptoms...... crank sensor just tells the PCM when to fire the coil, that part seems to be working ok.......

No codes is rather suspicious though...... if it has been running that bad, for that long, the PCM should have something to complain about by now...... The fact that it is not...... well, that leads to other questions.

 

Maybe you got a bad IAC or the pintle isn't seating properly. O-ring? This wouldn't explain your main problem, but shouldn't be making sucking sound.

 

Did you ever find a solution? I have the exact same symptoms and have replaced many parts/sensors and still nothing... anything helps!

 

I would agree with the Crank sensor MAYBE STARTING TO GO BAD.
When that damn thing dies (codeP0320), that's it you are Parked until replaced.
The only upside is it is a 20 minute fix if you are able enough to lay on/hug the engine and reach back there to switch it.
(when doing mine 2 days ago I had to lay my hip on the top radiator brace, hand on chassis next to the oil filter/exhaust manifold to keep balanced, and my shoulder on the passengers inner fender)

ANYWAY LET ME GET TO THE MOST LIKELY ANSWER FOR THIS ISSUE

I was thinking as I read the All the commentary, The problem is sorta obvious to Me.
The wandering backfire, sometimes intake, sometimes exhaust, then the rough idle, power loss/hesitation, all screams that the timing chain is stretched out of the acceptable limit.
With 185,K+ miles it would be of NO surprise if it was shot. That would be enough to throw the valve timing out of whack,and wander in and out of the correct zone.

[IMHO] I would be worried about it wandering far enough to have a Piston Dome collide with an open Valve and bombing the heads.

I replaced the water pump on mine even though was not leaking. I was looking to track a odd scraping/squeaking metal on metal sound. To Me the scary yet amazing part is even though the water pump did not leak, I could grab the Fan and rock it in any opposing direction with 1-1 1/2 inch of total travel (with serpentine off).

 

So, it seems for a little bit of insurance, you might want to carry a spare CPS.