I recently purchased a 86 Grand National 38k miles, having power, shifting issues, backfires, one had white smoke out of the oil dipstick tube, rough shifts. previously owner stated a tune up was in order, could that be a reason for this turbo 6 running so badly, or it is the rings, and/or transmission/turbo?

Shifting issues could be trans, white smoke could be a bad headgasket, tune would help, but most probably not cure the issues. Start with a tune up and go from there. I'd have a local mechanic look it over for you to see what the problems are and you can determine if you want to fix it yourself.

These engines need to be always TUNED. new air and fuel filters, fresh oil and filter. or turbo will suffer. I would change the transmission filter, and fluid. put a magnet in the pan, use a new gasket for tranny pan. always check fluid for metal shavings, smell of being burnt, foaming, etc. let your mechanic inspect your white smoke issue, head gasket could be problem, but lets move on, replace your OXYGEN sensor, every year, are your spark plugs and wires good, replace them, these engines need to be just right, no guessing. ALL sensors work together in case one fails. that being said, the most critical sensor is the MAS, MASS AIRFLOW SENSOR, if bad, you got problems. powerloss, shift issues, lack of performance, etc., etc., www.cardone.com can refurbish it. DONOT BY AFTERMARKET, GARBAGE ! it must be replaced with same. No substitutes !!!!!!! TPS @ THROTTLEBODY, (DRIVER DEMAND SENSOR) make sure its tight, and works properly or replace. MAP sensor, most overlooked, I experienced a problem with mine, when I was at a higher elevation above sealevel. ( believe it) this deals with atmospheric pressure, among other things. GET TO KNOW YOUR SENSORS, like your sex partner ! kapeesh ! if u know what makes them tick, your almost home, half the battle, yes ? I own a 1987 buick gn, bought it new off showroom floor, still have it, its been a great relationship, garage kept, seen no winters, ever !!! a beautiful machine !!! now, back to yours, change your oil to inspect it for coolant in it, (a head gasket, maybe). a blown head gasket would sound like an exhaust leak, with a pc of hose, 3 to4 feet long, with engine idling, go around base of heads. with your ear @ other end, listen for leak. next, make sure your fuel pump operates properly, hows the fuel pressure regulator @ throttlebody ? replace with same. REMEMBER, you don't know how this past owner treated this car. young guys just screw them up !!!!!!!! they must be cared for. they can take a beating, but, you must show them the love!! get this engine right, then get your tranny checked by a professional. not a thief, a good trust-worthy professional ! your fuel pump also has a relay, replace it. check all fuses. you bought this car as is, so, now you have to make it right, process of elimination, do u understand ? wonder how your coil pack is working, I replaced mine entirely. all the sensors, coil pack, etc., go back to the ecm(computer) which runs everything. the crank sensor is known to go bad, if hard-starting and backfire thru the throttlebody occur, these r syptoms. you also have a camsensor, so you see, a lot to swallow, yes? after your get this engine tunedup, take it to a buick dealer to hook up to an analizer to see what is working, and what isn't. $135.00 could be the best money you spend before you go all out. good luck my friend, KEN

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