Rough and shaking 350 after changing spark plugs

[newguy11]

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Attached is a vacuum diagram for a 1985 305 it may be of some help. The pic is of the EFE / Distr , tvs (grey thermal vacuum switch on the waterneck) and the egr / purge TCC, TVS ( black thermal vacuum switch that goes right into the manifold water passage)

These switches supply vacuum to various features at different temperatures. If you’re having problems when warm may be relevant. For example if you removed smog related parts and the engine os supplying vacuum to that circuit you may have a vacuum leak.

Can you tell us more about what engine work you did over the winter? How did the vehicle drive prior to the work ?

 

[newguy11]

by the way, anyone here who can tell my what that thing is for? saw that there is a cable attached on it which was loose, i think wasn't pinned in for a long time because its quite dirty in there

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I’m pretty sure that that brown thing with the 3 vacuum lines on the side of your air cleaner housing is part of your air temp setup. When is senses cold air it provides vacuum to the vacuum motor ( it’s just a door ) on your air intake that takes warm air off of your passenger side exhaust manifold

 

[Trucksareforwork]

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Attached is a vacuum diagram for a 1985 305 it may be of some help. The pic is of the EFE / Distr , tvs (grey thermal vacuum switch on the waterneck) and the egr / purge TCC, TVS ( black thermal vacuum switch that goes right into the manifold water passage)

These switches supply vacuum to various features at different temperatures. If you’re having problems when warm may be relevant. For example if you removed smog related parts and the engine os supplying vacuum to that circuit you may have a vacuum leak.

Can you tell us more about what engine work you did over the winter? How did the vehicle drive prior to the work ?

This is what came to mind for me too.

I rebuilt the exact UHJ system in your picture. If recall, The TVS that goes to EFE allows vacuum when cold and then closes when hot. Assuming the same or similar system, this should not be the OP’s problem.

The TVS that supplies the EGR allows vacuum when the engine warms up. I would check that set of circuits for problems.

I guess there is a chance it’s bad plug wires that increase resistance as they heat up, but I think this still sounds like a vac leak.

 

[Rustisbest]

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I don’t think this is your problem but it should be connected to your electric choke if you still have one

Might be the problem if the choke isn't opening. Making it run really rich after it warms up.

 

[Dave15]

hey guys, thanks for the new possible error sources, will check them today in the evening.
took out that brown little.."thingi" and looked closely there is no metal contact or pin inside which would connect to the losse cable.

related to newguy11 questions, all i fumbled around over the winter was changing sparkplugs, Airfilter, Oil&Filter change, resealed the leaking steering pump and took the opportunity to change all 4 belts.

 

[GTX63]

I picked up an 80 GMC 350 sb last year in between some other projects, so it mostly sits. The guy said occasionally it would cut out and sputter, mainly during wet weather. Ok, so I drive most project trucks for a few weeks to get a feel for them. No issues. Then one day it starts choking out; the cab is eye watering from the fumes and it will hardly idle. Plugs were sooty. The carb was new, the distributor was new, no vacuum leaks. It jerked so hard at idle it was like releasing the clutch with the e brake engaged. I'm about to pull valve covers for valve train damage and run a compression check when, for the heck of it, I pulled the cheapo Chinamade plugwires and put some on from another truck. The engine immediately smoothed out.
In 40 years of turning a wrench, I have seen bad plug wires, but not all 8 and not failing at about the same time.
Rule of thumb-never eliminate the simple and obvious until you check the simple and obvious.

 

[Gilmore]

Also worth check that during your tune up you didn’t loosen the distributor and it moved on you after you check the plugs wires and vacuum fittings as everyone correctly called out first.

 

[410 John]

What brand spark plugs? Use AC when possible and never Champion.

 

[ChrisGMoney]

Put a set of plug wires on it. The "wires" are nothing but carbon impregnated strings. You broke one or two when you pulled them off.

 

[Dave15]

hi guys, back after a weekend break, unfortunately i had no time to try search for the issue.
needed to spent some time with my lady.
tomorrow i will check the gaps and vacuum lines again.
i attached this pic, maby someone can tell me if these parts are a good quality.
@410 John , right now i have NGK plugs, as far as i could find informations on these the NGK´s are gapped to 0.035

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[410 John]

The NGK’s should work in a GM product. I use them in my Bug. As mentioned above, check them wires over.

 

[Ricko1966]

Get a spray bottle,empty windez bottle or such. Fill it with salt water,when it gets dark start spraying,plugs,wires,distributor cap. I'll bet you find a bunch of lightning,make the lightning go away and your truck will run right.

 

[newguy11]

Get a spray bottle,empty windez bottle or such. Fill it with salt water,when it gets dark start spraying,plugs,wires,distributor cap. I'll bet you find a bunch of lightning,make the lightning go away and your truck will run right.

I’m still of the mindset that his problem is vacuum related. Why are others pointing toward wires? He said the problem happens when the truck warms up. Does heat or expansion complicate the ignition system? I’m genuinely asking

 

[Ricko1966]

I’m still of the mindset that his problem is vacuum related. Why are others pointing toward wires? He said the problem happens when the truck warms up. Does heat or expansion complicate the ignition system? I’m genuinely asking

The reason I'm going with look for lightening is he said when he bought it the previous owner said it sputtered etc. when it was wet. Now what he has messed with is ignition,and his problem has gotten worse. You may very well be right he may have knocked a vacuum line off and created a new problem. But on day one it sounds like he had an ignition problem,we need to take the ignition out of the equation,before we start on a new equation. Also he said at speed he feels a rhythmic miss,a vacuum leak wouldn't be rhythmic a steady misfire on 1 cylinder would. He still should check for vacuum leaks,but after he has eliminated ignition from the equation. I don't want him hosing carb cleaner everywhere,just to find out it was ignition as it lights off.

 

[Dave15]

The reason I'm going with look for lightening is he said when he bought it the previous owner said it sputtered etc. when it was wet. Now what he has messed with is ignition,and his problem has gotten worse. You may very well be right he may have knocked a vacuum line off and created a new problem. But on day one it sounds like he had an ignition problem,we need to take the ignition out of the equation,before we start on a new equation. Also he said at speed he feels a rhythmic miss,a vacuum leak wouldn't be rhythmic a steady misfire on 1 cylinder would. He still should check for vacuum leaks,but after he has eliminated ignition from the equation. I don't want him hosing carb cleaner everywhere,just to find out it was ignition as it lights off.

i think you messed up the infos with GTX63 post, i never mentioned something about the previous owner or sputter when wet

anyway, i realy appriciate all your input and possible suggested solutions.
i ordered a new coil, distributer cap, rotor and wires and will change them, i also gonna check all the vacuum lines and thinking about buying new hoses and change all vacuum lines
just to make sure the old lady will run for the next years.

the ignition parts will come end of next week
meanwhile i will give a bit of attention to my mustang

does enyone know which sizes/diameters all the vacuum hoses have?