chevy1500cht

I have a 1996 1500 with v6 4.3. The truck has a bad miss when accelerating in the mornings but once it warms up the miss goes away and is.fine for the rest of the day. Will sit for ten hours or so while I'm at work and will.not act up in the afternoon. I've changed fuel filter, air filter, throttle position sensor, spark plugs, wires, cap, and buttom. I'm stumped please help.

Allan In NE

Put a pressure tester on the radiator and see if it will hold 17 lbs or so.

Allan

NeedMoTools55

As I recall that is throttle body injection. When you start cold you are in open loop as the computer is running the engine on preset specifications until about 118 ? degrees it switches to cloosed loop and can adjust based on senser imputs which will then cover up some problems as the computer see the extra air because of the O2 sensor reading the results compared to fuel (pulse width input). I suspect a good cleaning of the throttle body and drop a can of BG fuel system cleaner in a full tank will make major mprovements. You may need to pull the throttle body to clean properly. Otherwise I would spray a little cleaner around the TBI housing base to see if the RPM flares. If so you may have a leaking base gasket. I found one was actually loose. Replaced the gasket and it corrected the issue. Once I proved the gasket was the issue I went back and then did the cleaning otherwise I would not have known which was the root cause.

chevy1500cht

Thank you for the help I will check radiator pressure and check for throttle body air leaks then take off and give a good cleaning. Will post back my results soon.

chevy1500cht

I found no leaks around throttle body removed cleaned and put back with new gasket still need to check pressure on radiator. Will see if problem continues in the morning and let u guys know.

chevy1500cht

Forgot to mention no CEL on and in mornings truck will idle perfect and go wide open with no hesitations

oleblue92

Does this truck have a Plastic intake manifold? I had a 96 with a v8 and it had a crack in the manifold causing a slight miss on acceleration, although it did this all the time, not just when cold. My 96 also had smpfi (sequential multi port fuel injection), which is quite different from tbi. Hope this helps.

chevy1500cht

I drove this morning still bad miss and jumpyness when cold but did seem to not be as bad. Should I try sea foam spray that cleans the intake by spraying through throttle body while running?

chevy1500cht

Also when tightening throttle body bolts Haynes manual says 18 ft lbs. Is this correct because it bolts into plastic threads?

chevy1500cht

And oleblue yes it is the plastic manifold and I have sprayed hot or cold and does not detect a leak. I let truck sit this morning and started up this afternoon and no misses. I am assuming it has something to do with the cooler weather I'm stumped