Hello Scotty,
1987 Pontiac grand Am, 3.0L v-6 engine 2 dr LE, 318,000 miles, my mechanic told me that 3 cylinders were black carboned after using a camera, compression test indicated those 3 were low at or around 50 lbs indicating either worn rings or valves not seating properly due to carbon build up from improper fuel combustion. He had replaced the TPS based upon advice I received from a former GM service mechanic because engine has had a severe hesitation problem when starting out from a stop, but not when cruising or accelerating after starting out. Mechanic said it could have resulted by me using the wrong brand of plugs. Replacing spark plugs and there's a myriad of them available.... he recommended AC Delco or NGK. Now do I go with hotter plug or standard or iridium or what? Car does not smoke. But one can smell gas fumes. It was also discovered both exhaust manifolds are cracked and leaking. If I replace them, how can we avoid broken studs in the head? I have always changed oil between 3 and 4,000 m. Plastic timing chain and alum/fiber gears were replaced at 185,000 with steel chain and gears. Bought the car new of course in '87. One person told me to run half can Sea Foam in oil and the other half in fuel tank to clean engine. Fuel injectors never replaced. No knocks or weird noises. Also would a good radiator/engine flush be ok or could it cause some leaks? What recommendations can you give me and other tips to keep this old timer running and running better and what should I NOT do that would hasten its demise? Want to restore the car too. Thanks for all your videos and advice, I've told many friends about your videos.
compression test indicated those 3 were low at or around 50 lbs
It is very likely the engine is toast in which case the car should be scrapped. Do a wet/dry compression test to determine if piston rings are worn. A leakdown test will pinpoint valve problems.
Thanks, i was wondering how you could make the determination. Engine still has good zip. Had sat for a long time. Only the twice a month start up and warm up and short drive off road. Inspection ran out.
I would personally get the value pack of ATS cleaners… here’s the link… it includes an oil engine flush… and fuel system cleaner you put in the gas tank… it’s 60$ but trust me it’s worth it… I’ve done it on all my cars and it cleans up carbon deposits ALL inside the engine… as Scotty mentions in his videos quite many times… these guys who designed this spent 1 million dollars reviewing and studying carbon deposits… ones a computer engineer and the other a master mechanic… the carbon in your fuel system and in your oil are two different types of carbon and both require different treatments in order to remove them. Just trust me… use this product, and it should improve the performance of your engine… but after you use it. Keep buying fuel injector cleaners at your local auto parts store until you notice it fully fixed… (get the ones with PEA the other fuel injector cleaners are like snake oil products they aren’t effective) do this before you dump any expensive money into the repair of the engine…
https://www.atscarbonclean.com/product/2-pack-fuel-oil-pour-in-treatments/
Good morning new poster!
Do me a favor and break up your post into individual question threads. It will reduce confusion and make it easier to get direct answers for you.
Thanks
remedy for it.
replace vehicle
Manifolds cracked for a long time
[Camera reveals blackened cylinder walls. ( modified previous question.)]
'87 Pontiac Grand Am 3.0L v-6 automatic 318,000 m. Mechanic says 3 of the 6 cylinders have lower compression near 50lbs. Told of two possibilities: Rings wore or valves carboned up. Input welcomed of proving cause and remedy for it. Thanks
Making multiple posts about the same problem is against forum rules. If you have new information regarding an existing post simply add it as an answer or comment. Please keep this in mind for the future. Thank you. (Topics merged.)
