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Discussion Starter #1
This 84 bluepra I picked up at auction Saturday has slight sputtering or spitting eminating from the exhaust. Engine idles very smooth until it warms up, then the spitting starts. Can definately feel the spitting holding hand over the tailpipe. Engine RPMs remain constant throughout despite spitting. Have not done compression test yet, but vacuum gauge shows a rock steady 21 in. Acceleration is smooth and strong in fact, seems to run great at any speed but idle. Starts on first crank every time, revs high, then settles back just like its supposed to. Spark plugs look OK and appear to be fairly recent bosch platinum tips. Have not yet checked resistance on plug wires but they don't seem brittle at all (says sumitomo on wires, not sure if they are original). Already swapped a new dist cap due to much corrosion on the tabs inside. Listened to each injector with stethoscope, they seem to be clicking in perfect rythm. EGR valve operates buts does not cause stumble so I suspect thats plugged so a leaky egr doesn't seem to be the problem either. Have checked all plastic and rubber intake plumbing and vacuum hoses thoroughly for vacuum leaks and don't appear to be any. Appears to have original cat - could that be partially plugged and cause this symptom? What else to check in what order?

Phil D.
 

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Phil,
If the plug wires are the original wires, there will be a year printed on them in White (1984 in your case). A newer set of OE plug wires will have a later year printed on them. The OE wires can be a real PITB to diagnose! The outer insulation may look just fine, but the inner conductor is made up of very fine wire wound around a silicon rubber core. The fine wire can break at any given point along the length of the plug wire and cause arcing to occur at the break inside the outer insulation, and out of view. The arcing eventually makes its way through the outer insulation to a good ground on the engine. The most common area for the fine wire to break is right at the plugs from someone disconnecting the plug wires by pulling on the plug wire itself instead of the rubber cap. :mad: Try checking for arcing to ground by running the engine in the dark and looking for sparks from the plug wire(s) to ground.
Did you replace the rotor when you replaced the distributor cap? 8)
 

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Check the gaps on the plugs as well to see if they are within spec. and not set too wide. Has the black cover or the seal plug for the idle mixture air screw on the AFM been removed from someone tweaking the spring or adjusting the air bypass screw?
 

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Discussion Starter #4
By golly, they do say 1984. Thats a useful tip. No arcing that I could see. But its a little quieter now than it was earlier in the day and as I was twisting the wires around to look for the year I could hear the telltale crinkling cellophane sound of the cores disintegrating. I've cut open a set of original wires before and indeed the conductors just turn to dust. I guess I wasn't expecting to see an original set still on the car after so many years. I do believe that whether its the problem or not, these wires have outlived their usefullness. I will try another set tomorrow off my parts car if they aren't original too and check the resistance on these.

Phil D.
 

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I wonder if properly grounding the engine and tranny would also help?

Hosam
 

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Discussion Starter #7
supraii said:
pdupler
Did you wash the engine before this happen?
thanks!
No and I don't think the previous owner ever washed the engine or anything else for that matter. BTW, a new set of plug wires made a great improvement in idle quality. Still needs much work as the valve stem seals leak and the EGR is plugged. Eventually will get around to everything.

Phil D.
 

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change the plugs. put some non resistor type copper plugs in. my 85 did the same thing when i got it and abunch of the plugs were fouled pretty bad. if the wires are that old, chances are they didnt change the plugs much if at all. set of plugs is less then $10
william
 
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