Engine runs ehh not good

[LFR]

Everything has checked out in my 86 k10 swb with 305. The truck only has 47000 original miles on it. But it runs horribly. I don't think the plugs or wires have ever been changed but even at 140 degrees f it sputters and dies going into any gear but once it reaches 175+ it's just fine. Why does my engine run so bad. I mean Ik plugs and wires, cap, rotor need changed as they never have been but I have a darn good feeling that that won't fix it all. Idk maybe it will but I'm super skeptical about it. The carb probably needs rebuilt but it sounds like it needs the ignition timing advanced. any one have some thoughts

 

[Skweegle89]

A tune up sure wouldn't hurt anything.


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[Boone83K10]

Check the choke, should be fully open when hot and fully closed when cold.

 

[chengny]

2X BenBoone's suggestion. In MI during the winter -on a cold morning the choke plate should be fully closed after a prolonged shutdown. The plate should be in this position:

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After the engine has started, the choke heater coil will immediately begin opening the choke plate. Within 5 minutes or so, the choke plate should be fully vertical. Like this:

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If either position as shown above is not obtained, the engine will run poorly. No choke when cold is hard to start and warm up. Fully choked when warm starts easily but runs poorly until it is open (the choke is usually sticky and pops open all at once after driving awhile).

Sometimes it is just out of adjustment. Setting the choke is wicked easy. But if you haven't done it before, it should be done in small steps over the course of a few days.

Loosen the three screws indicated in the image below and adjust the choke by turning the black plastic coil cover. I don't always remember which way to turn it but you'll figure it out as soon as you move it.

If, on a cold morning, the choke is open (when it should be closed) - loosen the screws and rotate the coil cover so that the choke plate closed firmly. Rotate it back the other way and bring it to the closed position again. This time however, instead of bringing it over hard - rotate it gently until it just barely seats. Lock the position with the screws, start the truck and drive away normally.

The next cold morning (or after a couple of days), pop the air cleaner cover and check your work.

If the choke plate is closed when you do the initial check, it may be the case that it is not opening fully or quickly enough (or it is just sticking closed). The following adjustment is the opposite of above - i.e. it should be made on a warm day (or in a heated garage) after the engine has been drive and is all warmed up.

If the choke plate is found to be closed on a warm day - with a warm engine - just release the 3 screws and rotate the coil cover whichever way make the plate open. Do the initial setting as above. First bring the plate open firmly, back it fully closed and then bring it back to wide open again (but gently this time).

In my experience, a choke that does not open (or is stuck closed) makes the engine run worse than a choke that does not close at all.

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[79K10]

yeah ^^^^ cap, rotor, wires, plugs, time, spray carb cleaner - tune carb, time, tune carb. lol
... post pics!! and/or video lol

 

[LFR]

So does the choke automatically come off full choke cause it did this summer once but when I started it cold it never came off do I have to pump the pedal once or what? Thanks for the help guys

 

[chengny]

So does the choke automatically come off full choke - Yes, if it is working correctly.

Also, while it would open by itself eventually - just by virtue of the fact that it is near the heat of the engine - most carburetors are equipped with an electric choke assist to speed up the opening rate. This is an inductive coil (it's under that black cap - the one described above to adjust the choke close temperature with) and it is supplied with 12 volts as soon as the engine starts and oil pressure is developed. The power is applied when the contacts in the oil pressure switch close and it is led over to the choke assist heater via a light blue lead. The end of the wire and the connection to the coil is shown here:

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but when I started it cold it never came off

Not really a question - but I'm sure you are asking why the choke didn't open.

hard to say without looking at the situation. You are aware that the choke plate opens at an extremely slow rate - even with the electric assist - correct?

IOW you can't detect the opening by watching it. You have to walk away and let the engine warm up and the choke heater do it's job. It still takes about 5 minutes.

If you mean it didn't open and you waited and watched for an hour or so - it was probably stuck. Very often all that is required to get a choke operating freely is a good wash down with carb cleaner.

do I have to pump the pedal once or what?

It is good practice to pump the gas pedal at least once before a cold start.

Fully depressing the accelerator pedal before a cold start does three things:

1. It strokes the accelerator pump which sprays a shot of gas down each venturi. This aids in starting the engine when it's cold.

2. It allows the automatic choke to close the plate

3. It sets the idle to high, via the high idle cam.

 

[Boone83K10]

You are confusing the choke with the fast idle. Tapping the throttle when it is idling high is only dealing with the fast idle. The choke is controlled by a 12 volt source and heat. A choke should open as the engine warms.

 

[PrairieDrifter]

You definitely need a full tune up and get the carb rebuilt, I bet it will run perfect. It's honestly not very expensive

Fuel filter
Plugs
Wires
Cap
Rotor

 

[Skweegle89]

What kind of carb are you running?


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[LFR]

There's my problem. I think I never let it open enough, see I started it and ran it for about 2 minutes and I thought it was idling high. Put it in gear and the thing moved fast. I admit my wrong doing but didn't know since I had just got the truck so I technically neutral dropped it. But I respect squares so it won't happen again. What confused me was I started it on about 50 and it backed off. Started it in 20 temps for 3 min and it didn't back off. That was my confusion is it backed off fast when it was warm but below freezing it didn't. Thanks for the clarification. What type of carb kit should I get for this q jet. Hmm thanks for the help

 

[PrairieDrifter]

I'm not really sure on a good brand for rebuild kits on a Rochester, but they are one of the best working carbs when they are tuned and fresh. I would also get your timing adjusted.

 

[shortboxchevy77]

Everything has checked out in my 86 k10 swb with 305. The truck only has 47000 original miles on it. But it runs horribly. I don't think the plugs or wires have ever been changed but even at 140 degrees f it sputters and dies going into any gear but once it reaches 175+ it's just fine. Why does my engine run so bad. I mean Ik plugs and wires, cap, rotor need changed as they never have been but I have a darn good feeling that that won't fix it all. Idk maybe it will but I'm super skeptical about it. The carb probably needs rebuilt but it sounds like it needs the ignition timing advanced. any one have some thoughts

Just so you know my 83 with a 305 has a slipped harmonic balancer, time it using the timing marks and it runs horridly. Time it by ear and its great, common issue with them.

 

[PrairieDrifter]

Timing it by ear isn't always as accurate as it should be

 

[350runner]

For a kit to rebuild your qjet I'd check out cliffs high performance. If your balancer has slipped I'd get new one or use a vacuum gauge at least

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