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73-87 Chevy _ GMC Trucks => Performance => Topic started by: Tazman on February 09, 2011, 07:16:33 am
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After testing and/or replacing everything from the fuel pump to the ECM I still have an uneven idle at times.I start it and it runs great,next time it will be uneven.I checked everything for leaks even put gasket sealer on the gaskets for the throttle body.The only items that have not been changed is the MAP sensor and the EGR.With 160,00 miles I wonder if the engine is startung to wear our.Any ideas?Thanks
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I forget if we said this before but with electronics they have to be acting up for them to test bad. Make a list of the parts you changed and post that to help us out more
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have you pulled the TBI apart and checked the fuel regulator diaphram?
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No I have no done the fuel regulator,my neighbor who is a mechanic said since the fuel pressure is where it is supposed to be that the regulator is fine.Could he be wrong about that?
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Yeah he could be wrong. The fuel pressure is fine up to the regulator maybe, but not necessarily after.
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yes, the one on my burb the spring was broken in 4 pieces. I had to replace it and all the regulator parts. My pump was putting out 15lbs, when you turned the switch, but bled off immediately when the pump stopped. Are you checking the pressure before the regulator or after?
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Bought the rebuild kit installed,checked for leaks and let it run for about ten minutes.During that time it ran fine,yet this morning it did the same thing.I start it up it runs fine for a minute or so and then the idle fluctuates bad enough you think its going to die.Frustrating.
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You rebuilt the regulator?
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No just replaced the spring and gaskets.Thanks
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Only the idle is effected? Did you disable the EGR system to verify that's not causing the issue? Does it do it at cold start up or only when it's in closed loop? Any DTC's? Did you check the TPS and associated wiring? Have you checked the distributor pick up coil and make sure the pole piece isn't moving around?
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Yes it is only the idle affected,did disconect the EGR no change with it.Yes only when cold and then not all the time.It ran great today but when starting tonight it did it from the start.The TPS has been checked and is fine as is the wiring,and the pick up coil was changed a month or so ago..Please forgive me but explain DTC's and pole piece?Thanks
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correct me if im wrong but a bad sensor lets say the egr will cause the engine to act up almost like its not there at all (egr) so if you unhook it and the problem still hasn’t changed then it still getting the same signal almost like it not there. But if you unplug the tps which you know is good it will act up cause it not getting that signal anymore. Are you still with me ??? So this being said (egr+engine= messed up idle) or if you disconnect the egr (egr-engine=messed up idle) then the problem should be the egr. Now since I said that like I said I could be wrong so don’t go out and buy a new egr wait till vile or someone else back me up so they can share the blame if im wrong. It just the way I test sensors almost like trying to find a dead plug/wire when you have a miss fire you have the engine running then pull #1 wire if the engine changes that means that that plug was working so you plug it back up and move on to #2 till you find a plug that doesn’t change the idle once you unplug it
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So you are saying the EGR could be bad,the only way I thought to check it was to unplug it and listen for a change.That has not happened.Is there another way to check the EGR?Thanks
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That's what I was saying. If you go to a engine that's running fine and unplug a sensor or egr then the idle will change.
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Irish,
I don't get what you are saying. The EGR isn't a sensor ??? it's an output actuator. Unplug the vacuum hose going to it and plug it. Hold the idle speed up around 2,000 RPM and manually open and close the EGR a few times. This should help clear any debris if it is being held open.
Did you check the coolant temp sensor?
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see that’s why I said wait till someone else agrees lol I know it worked for sensors just wasn’t sure about egrs
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Earlier today on this site I saw an article about a book that is helpful if you own a 73-87 Chevy truck.I firmly believe that books are a great way to learn,I have three that I depend on.Yet experience can not be measured by what you learn in a book,learning by doing just can not be beat.For this reason alone I have to say thanks to each person who has given me advice on the problem I had with my truck.I just tested the EGR vale and found it not to hold pressure,replaced it and can now drive and enjoy the truck I just love to drive,wash,polish and wax.Thanks again.you all are the best.