2001 Chevy Van Rough idling

2001 CHEVROLET VAN
85,000 MILES • V8 • 2WD • AUTOMATIC
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ZDUTKO
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Lately I noticed, that my Chevy 350 Cutaway truck/van has been idling rough. I attempted a tune up, new plugs, cables, distributor rotor, body and cap, but still the same. Took it to 2 different mechanics. Both find cyl #5 misfire about 137, and cyl #7 about 35 times, all others are good. Compression test shows same, #5 lowest, # 7 better, all others good.
The truck's performance is poor, burns more gas, and
I never got a clear prognosis from either, they said they will get back to me...never did.
Any idea what it could be?
Oct 2, 2009 at 8:44 AM
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MATHIASO
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do you mean c3500HD 1 ton P/U 2 WD 6.5 turbo diesel 8 cyl ?
I can't find chevy van cutaway truck/van 8 cyl.
get back to me if it is the first one.
Oct 2, 2009 at 6:16 PM
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ZDUTKO
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No, it's not diesel. Sorry about the bad description, it's a Chevy 3500 TK (that's how it's listed on the registration card...to me it's a Chevy van, with a box in the back, tool compartments on the sides.), 8 cyl, 5.7 liter, and it shown on the picture attached.


https://www.2carpros.com/forum/automotive_pictures/354002_Chevy_3500_2.jpg

Oct 3, 2009 at 7:25 AM
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MATHIASO
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This is the firing order of the van, look at the cylinders that are misfiring carefully.


https://www.2carpros.com/forum/automotive_pictures/46384_firing_order1_1.jpg

There are many sealing points withing the combustion chamber that must operate properly to provent lost of power. Spark plug gasket or seat: that is unlikely for two adjacents cylinders. Iintake valves, Exhaust valves, unlikely for two adjacents cylinders. Piston rings, unlikely for two adjacent cylinder. Head gasket: most likely for two adjacent cylinders 5 and 7 .
Oct 3, 2009 at 7:50 PM