Chevrolet Repair: loss of power, chevrolet s10 blazer, s10 blazer 4x4

Question
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Followup  Hi Van, Thanks for the advice. I cleaned the egr, when this did not help, I replaced it. This seemed to correct the problem at first. But it returned. When it returned I plugged the brake booster vacuum line, This did no good. Then as before it corrected itself. I then covered the egr inlets with gasket to block it off. The egr came from a discount parts store and I was not sure it was good. This seemed to help the most, the problem did return but did not last as long, only 2 or 3 minutes. Any ideas?   Tony
Question -
I have a 92 chevrolet s10 blazer 4x4 vin Z with the 4.3 liter v6. I started to experience power loss and rough running engine. It escallated into rough idle and no power. When it is running rough there is a bad smell from the exhaust. I replaced the plugs, plug wires, rotor button and distributor cap. This fixed the problem for about 10 miles and then it happened again. After stopping and idling rough for 5 minutes it changed and suddenly had power again. I suspect a bad coil or cadiletic converter. Am I on the right page?
Answer -
Hi Tony,
A plugged cat usually won't fix itself. I believe you are smelling the exhaust from the cat, but it is probably doing its job, and burning a rich exhaust.
I would check for a dirty or sticking egr valve. That would act like a vacuum leak, but could sort of clean itself.
A vacuum leak from a hose will normally remain there, but a leaking vacuum brake booster could be intermittent.
Heater-a/c controls that are vacuum operated could possibly change if the control lever is switched.
But I would check that egr valve. It is supposed to be cleaned occasionally.

Van

Answer
The EGR valve may have been closing on flakes of carbon, and that is what was holding it open for a while.
If your engine is loaded with carbon, it is entirely possible one of the valves in a head is also occasionally closing on some carbon, and allowing it to not seal.
Do a Google search for Sea Foam, and check this link.

http://www.automotiveforums.com/vbulletin/showthread.php?t=283211

Van