Retarding the timing will cool the combustion which will lower the Hydrocarbon number,it will run bad but after a passed e test put the timing back to an advanced state which may help with the stumble.
SOURCE: adjust timing on 1998 GMC K2500 pick up 5.7 liter
It has to be done with a scanner. You can adjust this distributor, but there are no timing marks to watch as you move it. There is a timing mark on the balancer and on the timing cover for referencing Top Dead Center #1 cylinder only, but it is only used for dropping the distributor in to get the engine up and running. A scanner is needed to properly adjust the timing. Connect the scanner and look for a data parameter labeled ‘cam offset’ or possibly ‘cam ******.’ It will be listed in degrees. Start the engine, and bring it up to 1500 rpm. Note the reading. If the timing specification is not within plus or minus two degrees of zero, you need to move the distributor. You can move the distributor with the engine running but the timing will not change. After you move the distributor, the ignition has to be cycled off to let the computer learn the new timing spec. Restart the engine, bring it up to 1500 rpm and see what the new spec is. You must repeat this procedure until you get the timing into the specification as mentioned above. Once you have it set to spec, the code should clear.
SOURCE: 1995 GMC JIMMY
I had a problem just like that on my blazer and it turned out to be the wire harness on the fuel injectors. It could also be your fuel injectors, had to replce mine at 85000
SOURCE: 1991 gmc med duty truck with 454 tbi ,backfires, no power.
By module do you mean computer? There's nothing wrong with it. Yea, replace all ignition components with new ones. New cap, rotor, wires and spark plugs.
SOURCE: Misfires 96 gmc sierra 5.0
I suggest you have the injectors tested by the dealer, the sludge buildup will not cause a miss fire. to clean the throttle body use carberator spray while holding the engine idle high.
SOURCE: fails idle emissions test hc
High HC?
****** ignition timing....this will lower HC but raise other values during test.
Do you have room to increase other values?
After test return timing to the most advanced position without spark knock under load for best MPG.
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*re-tested WORSE, not "worst" like I originally posted - WTH?
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