rikhemi

Hey guys, just switched out my spark plugs and did a compression test. I have a turbo s2k with 148k miles(10k miles on boost). I did each test WOT and the engine warmed up.

Results below

Started with Cylinder 1

Cylinder 1 --- 210
Cylinder 2 --- 220
Cylinder 3 --- 240
Cylinder 4 --- 245

From what i read, they can be different as long as its 5-15 apart. Is this true? What can be wrong with cylinder 1. How can i correct it or is this not a big deal since its still reading over 200.

Regarding the performance, the car runs fine and doesnt burn much oil. Normally have to put a quart every 1 - 1 1/2 months.

Attached a pic of the spark plugs.

Thanks

Billman250

did you unplug the injector connectors?

If you dont, fuel could wash the oil off the cylinders and you will get "cascading" results as you have. First cyl you check will be highest, last cyl you check will be lowest.

First cylinder you checked got washed with fuel one time.

second cylinder got washed once already, then twice when you checked it.

3 washes for the third cylinder you checked.

So on and so forth. Get it?

Billman250

proper comp test:

Warm engine
all spark plugs out
WOT
injectors unplugged
check cylinders 1-2-3-4

IF you get numbers that seem to bother you, do the test again and REVERSE your order to 4-3-2-1. See if your numbers are the same for each cylinder. If the numbers for each cylinder come up different, test with another gauge.

DO NOT pull the fuel pump fuse. injectors will still pulse and allow remaining fuel pressure to be sprayed into the cylinder, affecting the readings.

rikhemi

I performed the steps on following a DIY posted online.

I performed all the steps you mentioned except i did take out the fuse for the fuel pump before I started to test it. I removed all the spark plugs and coils and set them on the side.

I started with the first cylinder (Front of the car just to make sure I'm referencing the correct cylinder 1 properly) which ended up being the lowest number. Then i went to number 2, 3 and then 4. I then went back to 2 and then finally 1 since they were the lowest numbers and the numbers were the same for those 2.

I let it crank for about 5 seconds for each pull. Initially on cylinder 1, i did the first test not doing WOT and it was 205.

rob-2

Nevermind

buaan

Good info there from Billman (as usual )

rikhemi

The way I did the test was correct right? If so should I do a leak down test or keep on running it as it is?

Billman250

couldnt hurt to do it again with the injectors unplugged...of course you will need to warm her up again.

rikhemi

I dont mind trying it again but if the numbers dont change, should i be worried about the difference between cyinder 1 and cylinder 4?

Billman250

I would surely investigate further.

Could be botched VA, burned valve, who knows.