- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Back in the good old days, engines had various vac hoses that controlled other devices including the PCV valve. The idea was to use one of the vac hoses to pull SeaFoam directly into the intake and help clean deposits off the intake valves. Today's engines have very few such hoses. And in your case, the problem is probably dirty injectors or the throttle body itself. So I would put the seafoam in the gas tank, but also check the throttle body to see if it is gummed up. You can use spray carb cleaner if it needs to be cleaned.
check all vacumn lines and make sure they are all properly hooked up and none are pinched or cracked. i also had i similar problem on a 96 blazer also with the 4.3 and ended up being the throttle cable somehow got frayed from how it had been set aside and was getting caught up at the cable end could be another option for you
Here is a detailed summary on the procedure of how to replace the intake manifold gasket on a 1996 gmc jimmy;
REMOVING THE UPPER INTAKE MANIFOLD(PLENUM)
Disconnect Battery (may not be absolutely necessary, but a good practice to avoid shorting a positive wire to ground).
Remove serpentine belt.
Drain the coolant.
Remove air cleaner ducting and disconnect wires.
Disconnect throttle linkage and bracket.
Disconnect cruise control cable.
Remove brake booster vacuum hose at manifold.
Remove PCV hose.
Remove ignition coil and bracket.
Remove purge solenoid and bracket.
Relieve fuel pressure at test port.
Remove fuel lines and bracket.
Remove upper intake manifold.
REMOVING THE LOWER INTAKE MANIFOLD
Remove the distributor and label the spark plug wires.
Remove heater hoses and bypass hose.
Remove upper radiator hose.
Remove EGR valve?
Remove sensors and bracket on right side.
Remove EGR tube, clamp and bolt.
Remove PCV valve (and replace).
Unbolt A/C compressor and move it aside.
Loosen compressor bracket and slide forward, but do not remove it.
Remove alternator bracket bolt (or remove alternator and set aside)
Unplug all vacuum lines from intake manifold.
Unplug all electrical connectors from manifold.
Take note of the intake manifold bolts and mark the location of the bolts.
Remove intake manifold bolts, and manifold.
Clean mating surfaces
THE MAIN INSTALLATION
Set the new gaskets in place and apply silicone to flat areas on front and rear of engine block.
Apply thread locking compound to manifold bolts.
Install the manifold and tighten bolts to 35 ft-lbs, in proper sequence.
Install the distributor.
Install the upper intake manifold.
The remaining installation procedures are basically the reverse of removal.
In the engine compartment, locate black vacuum hose that runs from brake booster check valve to intake manifold, there will be a small vacuum hose attached to check valve at the power brake booster check valve. This is the vacuum line going to the heater control unit,check the hose all the way to the firewall, repair any leaks you find. And that should take care of your problem.......GOOD LUCK
You may have to dig deeper for a vacuum leak. It's possibly the intake manifold gasket. Try spraying some starting fluid around the intake manifold. Also try disconnecting the brake booster and plugging that hose, the diaphram in the booster could be ruptured, causing a vacuum leak. Check the PCV valve and hose too.
mine is doing the same, it's your pcv receptor on the manifold. that hard plastic cover is actually part of the intake itself, if it "came off" it would cut your intake in half. that seem seals the two halfs together. you gotta pull the whole intake off and replace it... or jimmy rig it.