PCarSD

Im having a PPI done on a turbo Tip and I have to admit my jaw dropped when I heard the cost of the compression test. Two questions:

1. Do I need the compression test as part of the PPI? Car ran strong during test drive (with me as passenger and driver).

2. Is it possible to infer compression issues through Durametric generated log files? If so, what combination of values?

PCarSD

Is this a stupid question?

rmc1148

I'm no expert with Durametric. but most as far I've seen do not get compression check with a ppi not that it wouldn't be good info. If the miles are reasonable and maintenance has been kept up I wouldn't sweat it.

Turbodan

If the car showed a lot of stage 2 over revs and the car has not been flashed then I definitely would do a compression and leak down test. It should not be more than $300 for the test. To answer your question durametric or any other code reader would not show compression.

PCarSD

Thanks, it's a TIp so no type 2 over revs

And I understand there is no direct compression measurement from Durametric, but you can log values from a number of different sensors. My question is whether or not there is any way to infer compression issues from those readings.

Turbodan

IMO no. I believe the only way to tell if compression is low is by doing the test

Macster

All you can do with Durametric is infer the compression is "ok" if there are no misfire error codes.

As for an actual compression test, a compression test won't tell you if the engine will run only that it will create some compression when cold cranked.

A compression test is better a diagnostics tool when the engine is sick or suspected of being sick. However, its value is diminishing as the newer engines - since 1996 -- have misfire monitoring and can flag a sick/weak cylinder by misfire codes.

A thorough test ride/drive is your best engine check out. Visiting the car with the engine dead cold so you can verify the CEL -- and other warning lights -- come on then go off when the engine is started and then you let the engine idle and warm up some while you walk around the car is good.

After some idle time -- I'd try to idle the engine long enough to check the oil level -- then have the seller take you on a test ride that gives the seller a chance to do the car as you intend to use the car.

The route should be around 15 miles long. This gives the DME time to run through the readiness tests and flag any problems.

Then back at the starting point you take the car out as a driver and cover the same route drive the car the same way. The techs tell me the DME tests the readiness monitors twice.

After this test drive then if you still like the car you give it a PPI.

The important thing is -- well, it is all important -- but in this context the important thing is to give the engine some run time and for you to experience the car in its natural state with the engine running and the car on the road being used as you will use it.

You can compression test the engine until the cows come home but a good test ride/drive is what will highlight any issues and this is "free".

An added benefit of the test ride/drive is the PPI gets the car *after* it has been driven and this usage gives any leak a chance to make itself known.