TBI, smoke and hesitation

[bp71k5]

sun finally came out so I wanted to do some hardware store runs with the k5.

Starts fine, but engine stumbles and misfires off idle and billows out smoke from the exhaust. Seems to get better or clear up at higher rpm when the truck has been moving. Then once I sit at a light idling, same misfiring. Then people give me the middle finger if they didn't get a chance to roll up their windows in time.

Any ideas where to look first? Haven't touched the thing in months. It's a TBI conversion, 350, no fancy go fast parts.

 

[6872xtc]

It has to be sucking oil somewhere, correct?
What transmission? A TH350 or 400 could let oil past the modulator.

I wouldn't think that a PCV valve would do that, but??

 

[ktmoutfront]

What color smoke? Blue means too much oil. Black is too much fuel.

 

[bp71k5]

What color smoke? Blue means too much oil. Black is too much fuel.

It's white smoke. Almost feels like a spark plug wire is off, but I checked all of them.

 

[bp71k5]

It's white smoke. Almost feels like a spark plug wire is off, but I checked all of them.

I thought someone was vapeing next to me until I realized it was me.

 

[Fordum]

Pull your plugs. The rusty one is the one with the cracked head gasket letting coolant into the cylinder. Better check to see if the oil is overfull, and how much milk you see under the oil fill cap.
Did you notice a slight hesitation in the cranking? If enough coolant is getting into a cylinder, you could hydrolock it.

Might be something else, but sure sounds like water getting into a cylinder.
Of course, unless you are running straight water, I would expect you to have noticed the sweet smell of burned antifreeze, so it might be something else.

 

[ktmoutfront]

Yep. He is correct. White smoke is water based.

 

[diesel4me]

Sometimes excess fuel makes whitish smoke too--if the engine has a fuel pressure regulator with a diaphram they can rupture and let raw fuel be sucked into the intake through the vacuum hose that operates it..
Could be 100 other things too of course..

 

[bp71k5]

Yep. He is correct. White smoke is water based.

Crud, that does sound like why it would hesitate and then clear up after the water got out. I'll check all the plugs. Looks like I gotta refill my rubber glove supply from HF and pull it apart.

 

[Fordum]

Crank it up one more time, and smell the smoke. Just don't inhale........
If it has antifreeze in the radiator you will smell the burnt coolant. If its gas, it will choke you down. Just make sure you don't have any open flames nearby.
If you are running straight water, you won't smell much, it will just be steam. Maybe some rubbery smell.

 

[bp71k5]

Sometimes excess fuel makes whitish smoke too--if the engine has a fuel pressure regulator with a diaphram they can rupture and let raw fuel be sucked into the intake through the vacuum hose that operates it..
Could be 100 other things too of course..

I thought about that too, but this has an electric pump and spring loaded regulator. I have had a host of water system issues so my fear is that those problems were just a warning about what just went down.

 

[ktmoutfront]

If it is running water or coolant in a cyclinder, that plug may be "new looking and clean". Water is a great cleaner of carbon.

 

[Fordum]

True, but if it sits for more than a day or so, that steam cleaned metal will rust. That was how I spotted the bad two cylinders in my Ford. The head gasket was leaking between them and letting water into both.
Both of them had rust on the spark plugs.

 

[ktmoutfront]

You are correct. A running and driving engine will keep them clean.

 

[bp71k5]

Pulled the plugs this morning and #7 let about a cup of water drain out. All the other plugs are dry and look similar to each other. At least it's a simple diagnosis.

Since I can sometimes see into the future, (where I expect to break off all the exhaust manifold bolts), are there any decent stock performance heads to replace the stock heads? Are the vortec heads worth swapping for these 69-72 heads?

 

[diesel4me]

You'll stand a good chance of getting all the exhaust manifold bolts out without breaking them off,if you cut or grind off the bolt heads and pry,wiggle and tap on the manifolds till they slide off the remains of the bolts...once the shanks of the bolts are freed from the casting,they usually will unscrew pretty easily from the cylinder heads..
I've removed many that way with my fingers--only a few needed vise grips or a small pipe wrench,stud remover to unscrew them that were rusted in the head--only have had to heat a few up to get them out..

I haven't had any experience with heads,I always just re-used whatever ones I already had--did a valve job,etc..never had one crack or fail and had to replace one so far..

 

[bp71k5]

You'll stand a good chance of getting all the exhaust manifold bolts out without breaking them off,if you cut or grind off the bolt heads and pry,wiggle and tap on the manifolds till they slide off the remains of the bolts...once the shanks of the bolts are freed from the casting,they usually will unscrew pretty easily from the cylinder heads..
I've removed many that way with my fingers--only a few needed vise grips or a small pipe wrench,stud remover to unscrew them that were rusted in the head--only have had to heat a few up to get them out..

I haven't had any experience with heads,I always just re-used whatever ones I already had--did a valve job,etc..never had one crack or fail and had to replace one so far..

Thanks, that's a decent idea.

 

[CK10]

are there any decent stock performance heads to replace the stock heads? Are the vortec heads worth swapping for these 69-72 heads?

Vortec heads are good but you'll need to change the manifold to match, not knowing what you have invested in that already you might be able to grab a new set of summit heads for less money in the big picture and gain more performance than the vortec head

 

[ktmoutfront]

Since you have already done the TBI swap, I would stick with what will run your existing tune. Changing head style may require a new tune.

 

[CK10]

Since you have already done the TBI swap, I would stick with what will run your existing tune. Changing head style may require a new tune.

By the time I replied I forgot this was about a TBI, I wouldn't mess with it unless you're gonna tune it. They're picky in stock tune and don't like to be messed with.