Chevrolet Repair: suburban sudden poor running, chevron techron, clean as a whistle

Question
QUESTION: Hi
A few weeks ago my 1989 suburban half ton 4x4 (350) started
to hesitate during my regular calm excelleration. Then, one day on my way home it totaly got very ruff and a couple of minutes later it stopped running all together and would not restart. (engine would not even turn over). Towed it home ($120! for 1 mile tow). Checked cap and rotor, they were worn and had some light condensation. Replaced them. Also replaced plugs and wires. Engine will start now but takes over 5 seconds in the morning to fire (didn't used to) and settles into a ruff idle that smoothes out after driving. And as far as driving goes it still does that thing like its going to die on me again. I.E seems to be ok then runs very ruff wont excellerate smoothly at all. When I park it and punch the gas the engine spins up perfectly! It's not bad gas as I've added that Chevron techron stuff and gone to a different gas station and the problem just keeps getting worse. I did notice that when I changed the "coil" wire   alot of white powder fell out over the coil... But could the coil really cause all this? Maybe the EGR valve? If so, where is it? I'm told it's probably not the fuel pump because my 89 doesn't require much pressure to run. Vacume leak? Where should I look?
I appreciate you taking the time for this.
Tom.


ANSWER: Hey Tom,

Two things you need to do first.  Make sure that that coil tower is clean as a whistle and put dieletric grease on it with the new wire.  The spark generated from it should be sharp and blue not fat and red.  You should hear an audible pop when cranking it over with a test light on ground and the pin end about 1-1/2 inch from it.  The spark will jump to the test light and it must be sharp and blue!
 Even though your system fuel pressure spec is 9-13psi the pumps fail all of the time.  There is no Screader valve to check pressure on those so an adapter has to be used at the filter by the tank or at the back of the throttle body.  
 The egr should come off its seat easily (tuck you fingers under the cap and pull up) Those EGR valves are pulse modulated and have an internal relief and they have a tendency of lifting of their seat too much when you put the vehicle under light load.  They can fall flat on their face when they get really bad.  Remove the two 13mm nuts and take the valve off and make sure the pintle is seating properly.  If it is leave the valves vacuum line off and take it for a drive.
 This is gonna be the last and the toughest thing to check.  The distributor shaft reluctor magnets have a tendency to crack and spin backwards affecting the ignition timing.  Take a very close look at them (the little wheel that the pickup senses under the rotor) and see if there is any cracks near the spline of the distributor shaft)  If you bring the motor up to TDC on a cylinder the little triangles should line up almost perfectly) I am leaning towards this because of the description of hard to turn over.
  Hope this info helps and good luck!

WAyne


---------- FOLLOW-UP ----------

QUESTION: Thanks for all the info. But, I'm afraid I am a bit of a lunk-head when it comes to tech stuff.
What is a "pintle"? And what is "seated properly"?

As far as the coil test goes, is there an easier way (for dummies) to see if the coil is OK. I just don't have the skills or ingrediants to perform this.

I'm, in my ignorence, edgeing towards egr or coil. When I
accelerate hard it sounds like the engine just doesn't want to, like something is impeding power, even when it is actually not trying to cut out and die on me at the time. Like spark isn't happening correctly. (I did the wires right, one at a time). I never smell gas if that is any help. Also, there is an audible pinging where there used to be none. I'ts not an octane thing, it just started with all the other symptoms...I miss my swell runner.

Don't worry, I'm not going to hang around forever bothering you. And again, thanks for your time.

Answer
Hey,

 That pinging may hold the answer to your problem.  A detonation ping happens when the air fuel mixture is ignited too early and flame prorogation hits the top of the piston before it gets to top dead center.  Its like running at a wall that is coming towards you.
 If you have a variable timing issue with too much advance I would have your ignition timing checked and most importantly mention about the slipped reluctor ring that is common for getting cracks mounted on the distributor shaft.

Wayne