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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: greenmonster on February 17, 2010, 06:59:34 pm
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My truck isn't running right.It idles a little rough and it shakes when I give it the gas but it cruises fine until I get to 60-65 mph then it start shaking.
I put new plugs,wires,cap,rotor,vac advance,fuel pump,fuel filter and fuel lines.I have a 1 1\2 old edelbrock carb.I tore it down and every thing looked fine.
I,m lost ,any help or ideas would be great.
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Sounds like an ignition miss. Pinpoint which cylinder is causing the missfire.
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How do I do that.
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pull a plug wire at idle if it doesn't change its you bad plug or wire. if you pull it and it gets worse its not your problem. did you change everything before the problem or after?
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I changed everything after the problem.I changed the coil too.
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what year is this
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75 with a 350
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pinpoint the cylinder that is causing the problem. Set the idle at 1,000 rpm. Short one cylinder at a time and measure the rpm drop. If each cylinder dropped it to 800 rpm for example except for say #3 cylinder, then investigate #3 cylinder. Are you sure you didn't cross #5 and #7 spark plug wires?
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Ok I'll try that.The pluges aren't crossed because it was running fine,then I didn't drive it for 3-4 days and when I drove it the problems started.That was before I put all the parts on it.
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I still can't figure out what cylinder is misfiring.I did a compression test just because and it was 145-155 psi,so I think that is ok.Could the module cause this or maybe the pickup.How do I test those.
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What carburetor are you running?
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Edelbrock 1406 about 1 1\2 years old.
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I put a vacuum gauge on it today and it was moving about 2 in real fast. Is that normal.
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Clarify what you are saying... ???
Take the air horn off of the carb. Clean out the inlet and remove the sock filters. Check inside the bowl area for crap. Check your float level and float drop. Make sure the needle and seat are working without sticking.
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If you are talking about the vacuum reading,it was moving 2in/hg back and forth fast.
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2inHg with it running like crap wouldn't make me think mechanical. Check the carb
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Ok I'll check the carb.One more question,can you hear spark knock with a loud exhaust.Today I advanced the timing to get the highest vacuum and it gave me alot of power but it is hard to start when hot.
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Cleaned the carb out last night,but haven't put it on yet.I pulled a plug to check the spark,it was jumping the gap and it would arc to the side of the plug.I never seen that before,is that normal.
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No it's not normal
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What would cause that.
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THE CERAMIC COATING ON THE PLUG MIGH BE CRACKED CAUSE IT TO JUMP LIKE THAT
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I'll check that.The problems started,then I did a tuneup and it still runs the same so Idoubt it's the plugs unless I got a bad plug.
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I checked the plugs and they are ok.The problem I found is a weak spark.The spark is orange.Any ideas!
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How's the coil and your connections?
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I have tried 2 coils,an accel and a factory.The power wire is fine but I cant find a ground wire.I assume it grounds through the dist hold down clamp.I pulled the dist and the clamp was dirty.I cleaned the clamp and the inside of the dist but haven't put it back in yet to see if it made a difference.
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No there should either be a ground wire under the cap cover or a ground strap.
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If you are talking about the ground wire for the coil it's in there.The plug that plugs into the cap returns to the dist. so the dist. has to ground out some where.The clamp is the only way I see to ground the dist. unless I am missing something but it was running fine the way it is.I'm going to put the dist. in later,I will let you know if I figure anything out. THANKS
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It all sounds good but you can take most the parts to the parts store and get them tested. Are all plugs that way or just one
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All the plugs are orange.
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I tried a different distributor and still have an orange spark.I even grounded the distributor body to the battery and it made no difference.Any more ideas.
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How are you checking for spark? What's the gap? What is the voltage to the coil while cranking?
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.035 I didn't check the voltage to the coil,is that the power wire going to the distributor.
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yes
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I would take the guts to autozone and get them tested if your sure its grounded out and all they also have a book that tells the Resistance the parts should have
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I'm going to check the power wire.I don't think autozone can help me,I have try a distributor from a friends drag car and it does the same thing
(orange spark)
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yeah i guess that would eliminate the distributor than, have you check the voltage yet? also run a jumper wire from your battery strait to the dis and see how that looks
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Any more ideas.I hooked a ground to the body of the distributor and a power wire to the battery and it didn't help.I really appreciate everyones help.
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How are you checking for spark? What's the gap? What is the voltage to the coil while cranking?
And use a spark tester to check for spark. It should be able to jump .080"
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It will arc from the plug to the block about an inch.It seems to be strong,but I don't know why it is orange.Is an hei suppose to have a blue spark.Maybe I'm going in the wrong direction.
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If your battery voltage is weak your spark will be weak but I do believe you are barking up the wrong tree at this point.
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Did you ever pull your plug wires one at a time and note the rpm drop as suggested earlier?
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No I didn't.I should try that.
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Do you think the timing chain could be worn.