Engine problem

[alc4819]

I’ve got a 350 with a turbo 400 trans, it’s having trouble starting and ides high sometimes, also when a load is put on it backfires and won’t downshift. Anyone else had a problem like this? the engine has a smog pump which I think might be the problem or the carb

 

[Bextreme04]

Need more details. Pics?

Sounds like potentially carb issue, timing issue, vacuum leak, low battery.... could be lots of things. When was the last time you set the timing and idle mixture screws. What carb do you have? Have you checked vacuum at idle? Have you looked for vacuum leaks?

 

[alc4819]

Here are a couple pictures, I haven’t had the truck long so I haven’t set the timing and idle mixture screws, I’m not even sure how to do that on this truck, it’s a quadjet carb and I haven’t noticed any vacuum leaks

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[born2Run83]

When you’re driving it, and is under a load or higher rpm and doesn’t downshift, what do you eventually have to do so it will? Or how does it come to a lower idle and stop to shut the engine down?

 

[alc4819]

Usually when it will not downshift I have to shift it into second. Sometimes I’ll get in to go somewhere and it’ll run perfect plenty of power and no problems at all. I also went to shut it off today and it kept hitting on a few cylinders, thinking it may be a carb issue

 

[1973c10]

Welcome to the site

 

[Shorty81]

Welcome, nice looking Chevrolet

 

[Rickf]

Is the "downshift" switch hooked up to the gas pedal and tested for power?

 

[Snoots]

Check the vacuum line from the metal tube to the modulator on the tranny.

 

[Babs]

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[78C10BigTen]

Usually when it will not downshift I have to shift it into second. Sometimes I’ll get in to go somewhere and it’ll run perfect plenty of power and no problems at all. I also went to shut it off today and it kept hitting on a few cylinders, thinking it may be a carb issue

Dieseling.... sounds like the timings off.

 

[Corvette Ed]

Welcome aboard from East Tennessee

 

[Craig Nedrow]

Dieseling.... sounds like the timings off.

Retard the timing, sounds like too much advance. Rotor viewed from the top turns clockwise, so loosen the dizzy clamp and turn clockwise just a little if you do not have a timing light.

 

[ballencd]

I'd start with a full tune up before I messed with the carb. You need to know where you are starting from.