Split second Acceleration loss

[G. Lantern]

Howdy,

So, I've recently experienced a problem with a split second, but complete, loss of acceleration following a solid pop/click noise in my engine compartment. It happens more often at hire speeds. My 84 is a second (fifth) hand Blazer with a generous mixture of Jimmy labeled products, as well as an engine I can only describe as a science experiment, of which I could provide pics if it'll help.
Other possibly relevant info-
The Carb has no EGR valve,
The timing has a previously been an issue
I just replaced my power booster, as it completely cut out.
The previous owners either took no care of it, or threw as many cheap parts at it as it took to make it run.

If anyone can give me suggestion that i'd be able to address myself, I'd greatly appreciate it.

 

[6872xtc]

I am going to guess that the noise that you are hearing is a back-fire into the carb. It would also result in a stumble, or loss of power.
What did you do for the previous timing issue? Do you feel that the timing is correct now?
A lean condition of the fuel mixture can cause a back-fire into the carb.
So how does it run otherwise?

 

[G. Lantern]

I was in another state, but a mechanic had to tinker an awful lot with it to get it to pass emissions. I have my doubts the timing is properly addressed. Also, do you think that replacing the chromed out carb with one that can take an EGR may help?

 

[6872xtc]

It has been a long time since I had to mess with EGR and a carburetor. But I don't believe that you need to change out the carb, maybe just work on the tuning.
Did you change elevation? That can have an effect on what the ignition timing and tune of the carburetor do for the engine.
If you have to meet emissions now, it may force you to either find someone in the area to tune things for you, otherwise you can take the time to learn more about the techniques of making it run right.

 

[G. Lantern]

No change in elevation, but I'm driving more now. I don't have to get emissions, so I do have time to learn. Is it safe to drive until I get her tuned correctly?

 

[6872xtc]

I would imagine that it is safe, annoying however...
I don't know how to explain how to check some of the items, at least not right now.
Maybe someone can think of how to explain stuff.

Sorry, I know how to help when it's hands on, but I don't excell in this scenario.


@diesel4me
Can you help out?

 

[G. Lantern]

Good to know.

 

[diesel4me]

Need more info--like just when does it "cut out" and for how long,and does it do it 100% of the time,or only when it feels like it ?..

First thing to pin down is if it is fuel or ignition related--or timing..

Some wild guesses would be maybe its losing the electrical connection somewhere,like corroded side post terminals, or a failing battery cable,poor grounds--that can make it lose power momentarily when a load is put on it..
A bad pick up coil in the distributor or a failing ignition coil could do that too..but so can a lack of fuel pressure or a faulty injector..

Pretty tough to diagnose these issues from my desk top--especially when I have no clue what year the truck is,what engine it has,if its fuel injected & computerized or has a carb !..

 

[6872xtc]

He already posted that it is a carb, in an '84.
The pop/click in the engine compartment is what I figured was possibly a lean pop into the carb , since he said that it happens at higher speeds.

 

[diesel4me]

OK,I must have missed that..

High rpm misfire/bacfire thru the carb...eeewww...every time I had that symptom,it was a flat camshaft lobe......hope it's not that!..

Easiest way to confirm a flat lobe is to pull off the valve covers and watch the rockers with it idling..
(oil will squirt everywhere so be prepared!--I have cleaned the rockers off with carb cleaner and used duct tape over the push rod oil holes to run the engine long enough to diagnose it without getting soaked and making a huge mess under the hood)
--the rocker (s) that's not going up & down as far as the others has lost its lobe...on all but one of my engines that ate cam lobes,it was the #1 exhaust valve that failed most often..

When an exhaust valve cant open fully,pressure builds up in the cylinder,and it escapes thru the intake valve when it opens..thus creating a backfire or "poof" in the intake....one 454 I had threw flames out of the carb above 3000 rpm,,it set the air filter on fire one cold snowy night...