You're buying a used car. Is the first thing you do a compression test? (pickup, selling)

[M3 Mitch]

Good points, on a 96 or newer car with OBD-II, a low compression cylinder would very likely set a code for misfire.

Although, the OP's car is an 88, so might not have that code (I know 87 Toys do have a decent OBD-I system, but don't think it looks at misfire).

Compression tests are sort of old-school anymore, and mostly for older vehicles.

[UpstateJohn]

I just start it up and listen. If theres something that would make me think it needs a compression test, I walk away. But I don't buy anything old enough to really need a CT, unless its one of my old tractors.

[Katana49]

Compression tests are ideally done with an engine that has been brought to normal operating temperature. The reason for this is that metal expands when heated, and so the pistons and rings will seat better when warmed up.

That being said, I've done compression tests on engines both hot and cold and the numbers didn't change much, only about 10-15 psi per cylinder (which still put the engine in spec even though the readout was lower when cold.)

[st33lcas3]

A vacuum gauge can tell you a lot about the internal condition of the engine. It's quick to do, you unhook a vacuum hose and plug it into your gauge. You don't have to remove plugs, you don't have to use oil, and you can rent the gauge from parts stores. If you want your own, this one works for me.

Here's a page explaining what the readings mean. HERE

[rbohm]

Originally Posted by StickItInYourEar

Or, do you just drive the car with the radio off, making any and all observations and being sure to test every thing you can think of, including a full hard stop and testing the throttle and gearing, shutting it on and off frequently as well to check for any potential issues there.

I sometimes see compression numbers listed in a used car ad, this almost makes me suspicious, as in, what prompted them to include such a thing, was there some kind of a problem? Just the way my mind works.

Not only that but a compression test is most accurate cold, and then there is the wet and dry, your battery and starter will get a good work-out doing one...

first thing i do when looking at a replacement vehicle is check over the body, looking for signs of previous body damage and repair, signs of rust, etc. once i am satisfied with the condition of the body, i check the engine over. i first start it up looking for any smoke coming from the exhaust, and what color the smoke is.

i listen to it idle, searching for any unevenness in idle quality. when i take it fro a test drive, i do listen to the engine without the radio on, but i also feel the engine and how it runs, accelerates, decelerates etc. i also check my mirrors again for signs of smoke, and what color that smoke is.

i will also check the oil and the coolant as well, before driving the car. i will also fee how the transmission shifts, and listen carefully for any noises from the drive line, and feel for any vibrations that might exist that dont belong.

if i suspect anything, i will take it for prebuy inspection. i have done this enough times over the years, and with my background dealing with cars i know what i am looking for, if you have any suspicions about the car you are looking at, either walk away, or get a prebuy inspection.

[AlaskaErik]

Good luck on doing a compression check on some newer vehicles. It can take hours just to remove the spark plugs. Go to any dealer and start popping hoods on the floor displays.

[sj08054]

Originally Posted by StickItInYourEar

7MGE

1988 Toyota Supra

I'm asking myself what I would make of this ad, I know some of these cars get pretty hacked up. Especially in the NY area.. (I am not actually going to buy this, I just know it caught my eye and I'm asking myself what $3000 will fetch this year. Mental shopping.)

Oh and it's an 88, my fault.

88 Supra?


Of course someone would show compression number BHG was a common problem with the MKIII.

[Peregrine]

I've never done a compression test on a used car I bought.

[Tiffer E38]

For me, cars older than '96 are going to be project cars, so I don't care so long as it seems to be what it's advertised as, since I'll probably be replacing a lot of stuff anyhow. On cars newer than '96, then I can do an OBDII test to see if there are any codes or of the codes were cleared recently. Other than that, if it's running fine, has no obvious driveability issues (unless they are part of the advertised condition) and doesn't look to have accident/rust damage, then I look at the receipts to see if the common problem areas for that particular make and model are dealt with, or if I'm going to have to deal with them soon. If the condition matches the price, then it's good to go.

[Frihed89]

I pray, first.