Chevy Equinox hesitates at 40-60mph in top gear

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Old 10-04-14, 06:41 PM
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Chevy Equinox hesitates at 40-60mph in top gear

Chevy Equinox hesitates at 40-60mph in top gear. This is my dads car and I barely drive it but hear is what I know. When on the highway accelerating thru 40mph it starts bucking a bit, lay off the gas and it smoothes out, hit the gas starts bucking again. This is all in drive. I tried driving it in I (I on the gear shift) which I believe eliminates overdrive and it seemed to stop bucking. My questions, i have heard that the plugs and wires can cause this type of bucking-hesitation, any feedback would be suggested. Truck shifts fine otherwise, can it be that the top gear is messed up and the whole trans would need to be rebuilt to fix this issue or is there a overdrive repair? Some overdrive control? AWD, V6, 35,000 miles, my Dad babies this thing. Thanks or your help.
 
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Old 10-04-14, 08:01 PM
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A year for that car would have been appreciated.
But you likely do NOT have plug wires.
Common causes are fuel pump, vacuum/air leaks/EGR valve/dirty air filter. Air filter is the easiest to check on so start there.
 
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Old 10-04-14, 08:20 PM
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It's a 2007. Fuel pump will work fine unless under pressure ie highway acceleration? It does not hesitate off the line when you hit the gas at all. Shifts fine through the gears etc. air filter seems to easy.
 
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Old 10-05-14, 09:08 AM
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Yes, you do NOT have plug wires, you have solid state coil packs per each plug.
See, something is not ENOUGH for your engine in high gear. When you take off in 1st, gears ratio does not require full power from engine. Whilst cruising in high gear, say - overdrive, which is normally gear 5 or 6, depending on your transmission set up, you need a lot of "torques" to giddy up. That places load onto engine=fuel supply=oxygen supply.
Hence, my thinking that fuel pressure - or its supply - is not adequate; or, oxygen supply is not adequate; or, they are both adequate, but fowled by exhaust gas back flown from EGR. Fuel pump may be missing just that upper edge, fuel injectors may be clogged some, spark may not be the best for demand, EGR sticky shooting exhaust back into combustion chambers. Air/vacuum leak somewhere, changing air-fuel mix ratio.
It needs deeper digging, in, you know.
If filter checks out, do simple test. Have engine warmed up and running. Have can of brake cleaner with straw inserted handy, and start shooting quick cleaner bursts around the throttle body, air intake hose, and valve cover gasket. If at some pooint engine bucks - you have something going on there.
Otherwise, you are getting into things like leak tests, pressure tests, and such, with specialized equipment to be rented. If I were you, I'd have EGR removed and cleaned just for the heck of it, as in 8 years it's likely not quite clean anyway. And clean throttle body intake inside. Easy do. There are small passages inside of it, that get clogged by backflow gas from EGR quite easy.
 
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Old 10-05-14, 07:04 PM
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Thanks for the info on needing more power at higher speeds. Makes sense his peak horsepower on a engine is achieved usually at higher rpm's. Are you saying this truck does not have spark plug wires? FYI it does. Seems like it has a coil type distributor with plugs leading to the cylinders. I have changed coils before, I know what they look like.

Will check filter, run some fuels injector cleaner, check egr, spray for leaks, maybe pull a plug and see if its ok. Most likely plugs are fine at 35k miles but you never know. Come to think of it my dad does mainly city driving and I would imagine most trips the engine does not really get up to temperature and probably not a good thing
 
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Old 10-06-14, 08:01 PM
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As was mentioned it could be a few things but I would start by pouring some Seafoam into the tank to aid in cleaning the injectors, and have the OBD2 read for fault codes. A clogged EGR is a known problem with your 3.4 engine so I would have that cleaned up as was mentioned. Is the CEL on? (picture of engine seen on the guage cluster after startup). There could be a leaking plug wire also despite the low mileage due to vehicle age. I don't think your vehicle has a replaceable fuel filter as it is built into the tank so that can be ruled out. If it were my vehicle, and also own one of these, I would clean the injectors, scan for codes, and clean or replace the EGR. You could also spray clean the MAF sensor using the correct spray.
 
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