Truck sputtering In gear.

[Bowtie1216]

Hey guys, Just a question, When my 72' is in parks it idols just fine, but when i put it in drive it start shimming and shaking and sputtering? i changed my plugs not too long ago, and it still has power when i press the gas but it hesitates. Im out of ideals and i figured i'd ask you guys
Thanks a bunch

[NW_Ryker]

Mine does the same thing. Usually if I don't give it time to warm up or throw it in gear as soon as it starts. Interested to see whats causing this.

[68gmsee]

Non enough info but some things to check. If all of them check ok than it may be in the transmission or converter.

Timing. If you have an HEI start off at around 10 deg adv and play with it for proper response. Check for total advance also.

Vacuum leaks. Check around the carb, transmission modulator, power brake booster.

Choke adjustment.

Idle air screw adjustment in carb. Adjust for highest rpm or highest vacuum.

Check vacuum advance for leakage and make sure it's working properly. It should move with mouth suction and it should move freely.

[Bowtie1216]

Thanks guys, i'm pretty sure that its my timing, but its getting progressively worse, Started it up this morning let it warm up and it died about 3 times.

[68gmsee]

You mentioned that it still has power when you press on the gas pedal. Does it mean that the truck runs okay after that or does it die?

Reason I ask is my old 69 did that on me once and it turned out to be the fuel pump not pumping properly. Had a tear in the diaphragm.

Remove the coil wire to distributor and check to make sure the pump supplies at least a pint of fuel into a platic jug in 30 seconds or less. If you can get a pressure gauge, that would be better way to check for around 4 to 4.5 psi of pressure give or take a slight amount.

[fastwillie 696969]

check for vacuum leaks

[John Fabris]

Change your plug wires. For me, anytime I have had a engine run good in Park/Neutral (translation, no load on engine), and then run crappy and misfire in gear, is has been the plug wires. As you put a load on the engine, more voltage is needed to fire the plugs, and if wires are going bad, they will misfire or discharge onto nearby metal instead of the plugs. Try running your engine at night, with no lights, and have someone put it in gear and stand on the brakes and rev it up while you look at the engine in the dark. If you see a lightning show, them is bad wires.

[ChevLoRay]

We are assuming you have an HEI. If you're still running points/condensor, then beyond the obvious cap/rotor/wires.....you have some more things to check.

If you do have an HEI, then be sure your cap/rotor/wires are in good shape. Have you had a lot of rain? If so, moisture could be an issue....wires or within the cap. Look for arcing, carbon tracking within the cap, etc.

If you suspect a vacuum leak, remove the air cleaner ass'y. Place your hand(s) over the carburetor air horn. If the engine chokes down, you probably don't have a vacuum leak. However, if your attempt to smother the carburetor doesn't keep it from running and it (in fact) smooths out....you need to find the vacuum leak. I've used starting fluid sprayed along the junction of the intake/heads to see if there is a vac leak. A leak will make the engine race. Be sure that it isn't getting into the carburetor....keep the air cleaner on while using the ether. Some people have drizzled 30-wt oil at that same gasket area, but that creates a mess.

Vacuum advance on the distributor is another vague possibility. Make sure yours works properly. With that idea, there's the choke pull-off that may be leaking. It works off of vacuum.

If you don't know how old your vacuum lines and hoses are....might be a good time to change them all. Vacuum modulator on the transmission is another possibility. Vacuum lines to the heat/ac should also be checked.

But, if it is missing...it's ignition, vacuum or fuel.

[Autoblueprint]

Originally Posted by Bowtie1216

Hey guys, Just a question, When my 72' is in parks it idols just fine, but when i put it in drive it start shimming and shaking and sputtering? i changed my plugs not too long ago, and it still has power when i press the gas but it hesitates. Im out of ideals and i figured i'd ask you guys
Thanks a bunch

Originally Posted by Bowtie1216

Thanks guys, i'm pretty sure that its my timing, but its getting progressively worse, Started it up this morning let it warm up and it died about 3 times.

Check your readings: