86' C10 Engine Hesitation upon Acceleration

[tsmith]

Hey everyone, I was wondering if I could get some advice on a problem I'm experiencing just recently.

I was riding in my C10 yesterday and all of a sudden , it started the hesitate when I went from idol to acceleration. It idles perfect and when I get up to speed it's great, but between 0-5mph I'd say, it lacks power and I can hear it rev up a little and then back down. It's hard to explain. It sounds like a vacuum issue as it did this one time before and I found one of the vacuum lines disconnected. This time however, they all look to be in order.

I'm not sure if this has anything to do with it, but I just had long tube headers put on it about 2 weeks ago. I don't see how that would affect it. Just some info.

What should I check? Should I replace all the vacuum lines? I cleaned out the carburetor.
I'm still learning on these trucks so any input is greatly appreciated!


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[Eastonfrench]

Just because all of your lines are connected, doesn't always mean you don't have a leak.

Try taking carb cleaner and spraying it around any place that you think you could have a vacuum leak. if there is a vacuum leak, you will hear the motor react to the carb cleaner (usually the motor will rev up momentarily.

Good Luck

[tsmith]

Awesome, thanks for the advice. I'll do that as soon as I get home.


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[tsmith]

So I sprayed some carb cleaner on various vacuum hoses connections and when I got to (I think) the intake vacuum fitting, the engine started to rev. I removed them and I'm gonna get replacements.


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[Eastonfrench]

Sounds like you're on the right track.

[tsmith]

Okay so, after replacing the vacuum lines, I am still have the hesitation. And I may have understated it a bit. It seems to be doing it randomly throughout acceleration all the way up to cruise speed. I am wondering about the carburetor now.  I have a Weber 4 barrel. I have never worked on carbs before so I'm trying to learn. Also what are some other things to look at? Accelerator pump? I'm thinking it needs a tune up, but it's throwing me off because it was running fine a week ago, and  a day after I got my new long tube headers installed, it started this. Not to say it has anything to do with it, because it ran fine initially.




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[tsmith]

It also seems that I have a ton of vacuum lines. I took a picture of this one in particular because I have no idea what it is. It goes to that sphere in the right side of the engine bay.



Thanks for the help, I'm learning as I go.


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[AZ87V10]

That's the vacuum storage ball for your HVAC system and the factory vacuum actuated cruise control. You need that for the system to have enough pressure to operate all the blend doors correctly so the air goes where you want it from the control head. Are you sure you're not getting cross fire on those plug wires? They look awfully long and jumbled together.

[tsmith]

Okay gotcha. And no, they were all neat but I moved them when I took my valve covers off. I just took of my distributer cap and found that my HEI advance is seized and the weights are the only thing that moves. This could definitely have something to do with it right? I got an advance curve kit to replace the weights and springs but now I'm wondering if I need to replace the entire distributer.


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[AZ87V10]

It looks like you may have just found your culprit. I would at least replace the parts that are bad, clean up your plug wire routing and check your firing order, then check and reset your base timing. Timing and vacuum leaks play a large part in hesitation issues.

[tsmith]

It feels pretty good to have (possibly) found it! After researching. I saw that some people spray penetrating oil in there to free up the seize. It seems to be pretty stuck.


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[bd]

Okay gotcha. And no, they were all neat but I moved them when I took my valve covers off. I just took of my distributer cap and found that my HEI advance is seized and the weights are the only thing that moves. This could definitely have something to do with it right? I got an advance curve kit to replace the weights and springs but now I'm wondering if I need to replace the entire distributer.

I recommend against just spraying cleaner and lubricant into the mechanism while it's on the vehicle.  The solvents can attack the enamel insulation on the pickup coil.  The distributor should come out so you can remove and disassemble the shaft to clean and lubricate the reluctor and advance mechanism.  Replacing just the weights and springs will not gain anything by themselves and could actually introduce a new performance problem by altering the advance curve.  Be sure that the advance mechanism rotates freely before setting the base timing.

Tips:  Set the engine on TDCC #1 cylinder and make a mark on the intake manifold exactly in the direction where the rotor is pointing.  Additionally, make a mark on the intake where the advance can is pointing.  This will make stabbing the distributor and establishing base timing easier before initial startup following the repair.  Once you have the distributor out, there is a dimple on one side of the distributor gear just below the roll pin that retains the gear to the shaft.  During reassembly before reinstalling the roll pin, make sure that the dimple faces the same direction as the distributor rotor.

[tsmith]

Thanks a lot for the advice! I am going to take a break today and get back on it tomorrow. The advance  is reallllly stuck.


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[Eastonfrench]

A stuck advanced will sure do it. I have seen degreaser or Kroil sprayed in there to free it up. Definitely needs to be fixed.