Misfire when you accelerate

2001 CHEVROLET ASTRO
230,000 MILES • 4.3L • 6 CYL • AWD • AUTOMATIC
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DPSTITES
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I have a 2001 Chevy Astro that has 230,000 miles on it. I been having a misfire and chugging going on for a while, so I took it to a shop and the mechanic said it need a map sensor so I replaced it, which did not fix anything. I took it back to them and they said I needed a tune up which I had them do. Replaced fuel filter, air filter, distributor, plugs and wires still nothing changed. Paid $560.00 for repairs still no change. Took it to a second mechanic, he did a compression test and some others fuel pressure, electrical and he found one of the wires that the first mechanic put on arcing so he replaced a couple of bad wires, but still nothing changed. Then he told me I needed a crack sensor and a ground wire fixed this was done also. The second mechanic said that I should just get rid of the van after charging me $532.00 repair with no avail.

I am at the end of my rope with this now and would like to get some help if anyone has had this problem. Thanks for your help.
Mar 13, 2016 at 11:12 AM
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JOHNNYT73
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It could possibly be a clogged catalytic converter. A mechanic can do a back pressure test in the exhaust system if he has the equipment.
Mar 13, 2016 at 2:04 PM
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DPSTITES
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Thank you for a quick response. I took the van into the shop to day and both catalytic converter replaced. The van runs great good power but still dealing with a 4th cylinder misfire. I drove it today and the check engine came back on so I took it and had the code read and it is a misfire 4th cylinder. I replaced a lot of parts on this van. Any other ideas will be helpful.
Mar 15, 2016 at 6:41 PM
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JOHNNYT73
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Check the plug. Swap it with another cylinder and see if the misfire follows in that new cylinder.
Mar 15, 2016 at 6:43 PM
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DPSTITES
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You are awesome, thanks, I will try that. Great idea.
Mar 15, 2016 at 6:46 PM
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MIKE H R
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there may be a number of things but, check the fuel pressure, has the fuel filter been changed? Also with the enthonal in the gas now a days the screen that is on the fuel pump may be getting clogged with junk the ethenol produces. Happened to my wife's Firebird.
Mar 16, 2016 at 8:18 AM