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Post by tuns0ffun0 on Jun 19, 2009 17:06:27 GMT -5
hey guys i own an 86 chevette, daily driver. I recently have started getting terrible gas mileage and now when i get to and/or cruise at 70mph it starts to buck and lose power. Generally, i can slow down to 60ish and it kinda stops the bucking. I have taken it to several mechanics around where i live and nothing is different. it has been getting harder to start over the last few months before the bucking started and now its starting to buck at lower speeds. It doesnt start at a specific RPM range either.
here is what i have replaced: fuel pump(different reason) fuel filter, plugs, plug wires, distributer cap and rotor, air filter, the main computer box(transfered over the prom chip), O2 sensor, and just because it was time changed oil and oil filter.
i have no cat. converter, i have sprayed carb cleaner in carb, used fuel treatment.
we checked the distributer for play, checked the springs and weights(everything was fine).
i am at a loss and am stuck cruising about 55-60mph on the interstate everyday going to work. Any and i mean any input or help will be greatly appreciated.
thanks for your time.
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Post by hydroli on Jun 19, 2009 17:16:35 GMT -5
Do you have power brakes? It could be a leak in the booster brake or another sort of vacuum leak.
Did the mech checked compression? It could be a crack or a leak in the head and head gasket area.
Do you hear valve train noises? I experienced a similar problem with some of my chevette engines, oil pressure getting lower, lifter would discharge and engine hardly reving up.
Did you replaced EGR valve? It may be the cause of rough idle when it is deffective, maybe affect high rpm range too...
If you can tell precise details about how the engine runs I could come up with a better diagnosis.
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Post by tuns0ffun0 on Jun 19, 2009 17:21:01 GMT -5
no sir
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Post by hydroli on Jun 19, 2009 17:26:34 GMT -5
I modified the last post...
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Post by tuns0ffun0 on Jun 19, 2009 17:33:11 GMT -5
it idles rough. i have an exhaust leak which i havent fixed yet. the mechanic did not do compression check almost positive. the only noise i get is when it starts to do it and its kind of a...wokawoka when it starts to buck. i had looked at my chiltons and looked at the egr but havent replaced it yet.
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Post by tuns0ffun0 on Jun 19, 2009 17:55:12 GMT -5
also check engine light has been on for about 9 months. one mechanic told me the diagnostic had probably went out and i was having no problems at the time...when i replace the computer the check engine light stayed on. i tried to do the diagnostic and it still wont give me and error code,
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Post by hydroli on Jun 19, 2009 18:14:40 GMT -5
I suggest you to manually check the engine parameters; taking a remote mechanical oil pressure gauge, an infrared thermometer, a volt meter for the O2 sensor... check the compression and block the EGR valve.
It's all I can think of right now.
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Post by tuns0ffun0 on Jun 19, 2009 18:22:45 GMT -5
awesome i appreciate your help man. i will try those things
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Post by hydroli on Jun 20, 2009 9:34:14 GMT -5
You're welcome. Please come back to let me know what it was.
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Post by tuns0ffun0 on Jun 24, 2009 23:15:04 GMT -5
just figured i would add this...drove it and it started doing it again of course so i got off the interstate and took old highway...got a few more miles then died and wouldnt start...wasnt getting gas spray into the carb. thought sweet my three month old fuel pump was defective and causing the problem the whole time...replaced it...wrong did it again today and the severity and frequency are getting worse. gonna try and replace egr tomorrow...i love my chevette but its getting close to being someone elses chevette
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Post by hydroli on Jun 25, 2009 8:45:01 GMT -5
have you checked the color of the plugs?
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Post by hydroli on Jun 25, 2009 8:48:05 GMT -5
this way you can have a clue if it has something to do with the gas supply. White means not enough gas, black, too much. White spots on one or two plugs tells you that you have a coolant leak inside the combustion chamber.
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Post by hydroli on Jun 25, 2009 8:53:32 GMT -5
check for oil presure too!.. if it ever starts again. I had these problems with an engine that had not enough oil presure and too much gas presure. It could be one of these reasons. And of course, check for spark. I suggest you to go see an engine mechanic if you cannot test your engine.
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Post by tuns0ffun0 on Jul 13, 2009 19:14:44 GMT -5
well 400 dollars later...after replacing the fuel filter two weeks before it happened it turned out to be the little plastic thing in the fuel filter...angering...thanks for your interest.
150 of that btw was putting my brakes at 100%. mechanic was scared to drive it even though i had been driving it for 3 months the way they were.
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