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Discussion Starter #1
Just want to know what you guys think the most common/first place to look would be. I have a 1993 K1500 Burb. It idles great when you first start it, but after driving for a while then driving around the parking lot when you let off the gas the idle will drop like it is going to die (it never does completely die) then comes right up where it should.

From what I hear it could be, EGR Valve, MAP Sensor, Fuel Filter, or Fuel Pump. I don't mind replacing them all, but am trying to save a little money this month and need to take it on a little trip for Thanksgiving. So replacing the culprit the first try would be nice.


TIA

I am hoping its NOT the fuel pump :grrrrrr: DON'T want to drop the tank!!!
 

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The most common issue with bad idleing around here is vacumm issues, so you can start there. Unplugged frquently reccomends using a can of starter fluid and spraying starter fluid on different potential culprits. If the idle runs up when you hit a certain spot, you found it. Beware, using this method could potentially be dangerous, so be careful.
 

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I would kinda doubt the fuel pump but fuel filter is a possiblity. Crawdaddy is right its probably vacumn leak. Good luck
 

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How does the performance differ between neutral and drive? Could be something as simple as a bad plug or plug wires. I recently picked up an intermittent stumbling idle after some recent work. It idles rough in gear and smooths out in neutral. I'm thinking I have to go back over the plug change I just did, but haven't had the time.
 

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Discussion Starter #6
I just replaced the wires, plugs, cap, and rotor. It did the same before and after. I am starting to think it is the fuel filter.
 

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Discussion Starter #7
Any new ideas? So far plugs, wires, cap, rotor, o2 sensor, fuel filter, and oil change. Still the same thing it will drop to like 100 rpm and idle all rough.
 

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You might want to try unpluging the IAC and MAP sensers when it is running rough. if theres a change in the idle u have most likely found your problem. It should kick in to default mode if u unplug either one for a short time.
 

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not to be an a$$ but have you checked the computer for codes? that be a good start. i just got a truck that a mechanic of 35 years told the customer the head gasket was junk and he wanted $2000 to fix it so they dumped the truck to me for free. i started it and the cat went to bright red on the pass side and it was boiling the heater hoses. i put the code reader on it and the ignition moduel failed it test. i replaced and all was good and i tried to give it back to the owner but they said it is yours and it is now going to the Youth group of our church for money for the group. sometime the computer will tell you wat is wrong (some times it does not but a good starting point)....mike
 

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moment you step of the case at a red light she would rough idle like she was going to stall and you want to keep the foot on the gas to keep her running ....

it's the o2 sensor going bad
 

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Discussion Starter #13
more info

Ok I have been posting about idle issues. I have replaced the cap, rotor, plugs, wires, fuel filter, IAC valve and rebuilt the fuel regulator. Now I think it is giving it too much fuel at idle. If I give it gas then let off it drops to almost 0 RPM then will kinda come back up. But I just did it and as it was dropping rpm I gave it a little squirt of starting fluid and it died immediately. Do you guys have any suggestions at all?

1993 K1500 5.7L
 

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you might wanna check timing, I always have when I mess with cap and rotor, just a few degrees off, and it will seem to run fine, and then stumble when computer is adjusting
 
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