Was the idle ok before the tune-up, or was there no change before and after tune-up?

It was worse before i think, a little better know. Any other suggestions?
thanx
jim

It's probably not the fuel filter since you did not say anything about the engine bogging down under load while at highway speed, for example, climbing a hill.

Make sure that all vacuum lines are in place, none pulled off.

Check the ohmic resistance of the ingnition leads. Don't forget the high tension coil lead too, if present.

Check for an EGR valve stuck open.

Don't burn you hand doing this check! With the engine idleing, place your hand over the exit of the exhaust pipe. You may wish to put a rag in your hand, or use some other object to restrict the exhaust pipe. For a proper operating engine, you should feel even exhaust pulses. If one of the pulses tends to "suck" instead of blow, that exhaust valve is leaking. If one or more pulses are much weaker than the others, suspect a leaking intake valve or other valve train problem.

Check the valves. Run a compression check. If the compression is low, test to find if the lowered compression is due to valves or rings. To do this, add about 1/2 teaspoon of oil to the offending cylinder(s) and retest. If it was worn rings, the compression will improve.

Test for worn valve cams. One cam worn more than its mates will cause an uneven idle. All cams worn down will cause reduced power.

You mentioned a rotor kit, so I presume that your engine has a distributor. Check for a worn distributor bushing. A rotor shaft running off center will cause the engine to lope at idle but is not noticeable above 1000 rpm. This condition is best seen on an oscilloscope ignition analyzer. Set to display all ignition firings on top of each other. If all are equally spaced in timing, all will be on top of each other, but if they vary in timing, it will be obvious. I have seen timing variation up to 8 degrees due to a "wobble" of the distributor shaft and/or out of round distributor cam. Look at the parade of ignition pulses. Is there an obvious difference in one or more of these?

Check for a leaking intake manifold gasket.

I wish you luck. Tell us what you find.

This may be a dumb question, but how does one check for vacuum leaks???
thanx
jim

How to check for a vacuum leak? Not a dumb question! I don't know all of the tricks either. There are others out there like John_g who knows a lot more about this than I do. For what it's worth, I offer my tips.

1. Run a vacuum test with a gauge. Follow the instructions in the repair manual. Compare readings against the published normals. Start with the vacuum reading at idle. Also note if the reading is steady or has a pulsation. A restricted exhaust system will cause a low vacuum reading and may drift around. An intake leak will cause a low reading. Bad valves or valve train problems will lower the vacuum and may show a pulse if one valve is much worse that the others.

2. Visually examine the gasket-line between the intake mainfold and the head. An inspection mirror will be useful here. Look for out of ordinary appearances.

3. Are you mysteriously loosing coolant? And do have a V6 engine? If so, pull the dipstick and examine the condition of the oil. GM V6 engines have coolant passages through the intake mainfold between the heads and are known to develop leaks if the intake manifold is made of aluminum. Coolant can leak into engine oil pan. Engine oil contaminated with coolant may have a brownish color. A leak here may be accompanied with an air leak elsewhere.

4. After a road run at 35 mph or more, go back to your garage. Minimize the amount of time spent at idle since we wish to examine the sparkplugs after running at load. Remove the plugs and lay them out in the same pattern as in the engine. Are there any differences between the plug tips? Is one plug more white or slightly burned? If so, that cylinder is running lean and that may be due to an air leak nearby.
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At 223,000 KM (138,260 miles), worn valve guides are possible. A worn valve guide can allow the valve to tip sideways and break seal from forces of the valve actuator.

My truck doesn't have a rough idle just lack of power up hill...But I did have to replace 1 of the injectors on the throttle body before that did cause a rough idle...I would think you would have a throttle body and check to see if both injectors are spraying even..one might be working and the other just dripping ...just a thought to check...

There are a number of different ways to test for a vacuum leak, which BTW comes under the broader description of an improper air/fuel ratio and that can occur for a number of reasons.

Your task in searching for a rough idle is to first confirm if the rough idle is happening to one or more individual cylinders, or if it's totally random through the engine. By using a four gas analyzer I can measure the exhaust gases and find out if the computer actually has control of the engines air fuel ratio. Plus my engine analyzer also makes it easy for me to determine if the rough idle can be narrowed down to which cylinders are firing poorly. You will have to pull plug wires (off the cap to reduce getting shocked), or find another way to ground out the ignition for each cylinder as you search for the affected cylinders.

Now once identified if possible, you can concentrate on the causes. "Assuming" this is indeed a vacuum leak, one of the routines I use is to add propane to the likely areas and see if the extra fuel cleans up, or worsens the engines idle. You need to remove the PCV valve from the valve cover and shoot propane into the crancase to check for the most common leak in this engine, the intake manifold gasket. A second way to check for the intake gasket is to block the breather hose with one finger, and then use another finger in the PCV grommet to seal the crankcase. If there is an intake gasket leak, you will feel vacuum building in the crankcase, and you may even notice the engine start to smooth out once that happens.

Another way we test for vacuum leaks is with a smoke machine. By plugging this machine into a manifold vacuum line, and pumping smoke into the intake manifold, we can see leaks easily by following the escaping smoke.

The scan data from the computer showing fuel trim adjustments, combined with data from the four gas analyzer is used to determine if the injectors are feeding fuel at a correct ratio. Part of the testing here would again include the use of alternate fuel such as propane, to see if one of the injectors is restricted. By adding propane to the throttle body on the injector side that is leaner, it's possible to clean up the idle, and then while monitoring both the fuel trim data, as well as the four gas analyzer we can confirm if injector issues exist.

Remember, fuel ratio problems can exist for many reasons, EGR leakage, intake valve seal leakage, improper injection by either too much or too little fuel per pulse can be taking place, the cannister purge system could be faulty, etc.