Last Friday-9-6-13 I picked up a 87 Ttype with 78,000 miles, original navy blue paint, rebuilt turbo, new plugs and wires, new fuel pump, new Mas and a few other things. The only things wrong with it are the rattley windows and the rough idle. The dealer who rebuilt the turbo said on the receipt that the owner should use premium gas and the idle would smooth out. So I filled it from 1/4 tank, with premium plus some Gum Out injector cleaner. I took it for a hundred and twenty mile drive today and it seems to be smoother but still a little rough. Tomorrow I'm taking it into a tire shop to get the wheels balanced. At about 45-50 mph it starts vibrating. Not real bad but anoying.
So for $12,260 did I get a decent deal? Or did I get screwed?
The dealer said ...
That was funny.
Consider a Spring cleaning.
There should be a sticky for it.
Premium gas would have little to next to nothing to do with a "rough" idle"
Premium gas will have everything to do with you getting up close and personal with your head gaskets or rod bearings.
This is a force fed performance machine.
Always use the highest octane you can buy.
And for now - don't start tweaking that boost (Up)
Or - you'll enjoy the term "rebuilding my engine"
First -
Take an inventory of your cars performance items.
What chip is installed?
What size injectors
What turbo?
How much boost?
Etc.
And STOP putting those petroleum distillates or any other unknown mystery snake oil in your fuel system!
The correct way to clean gummed up injectors - is to remove them and clean the gummed up injectors.
These cars don't have the smoothest idle in the world to begin with.
Usual suspects - vacuum system, MAF sensor.
Maybe even the chip (open loop vs closed loop idle).
Install a vacuum gauge - and look - Depending on cam - should be between 12-17 in.
Stock should be around 16-17 inches.
(Gently) Tap the (Stock?) MAF when it is idling. Does the idle change?
"New MAS" (MAF) doesn't always mean "Good MAF"
Step 2 for you.
Before you start replacing things and asking tons of vague questions.
Buy a SCANMASTER.
Period.
Then you can see what the IAC is up to and the TPS readings.
What is an IAC and TPS you say? And how are they adjusted? Start reading. A lot.
If you want to change some things - start with any old 25 year old rubber vacuum lines, etc.
And oh - THE ENGINE OIL!!!
2 cents worth.
Go slow.
Small small tweaks while you learn the car.
Keep the go-fast stuff to a minimum until you get things running to your liking and you feel confident the basics are attended to.