89 249sx DOHC KA problems

[hoang]

i also posted on freshalloy, but hopefully i can get an answer here as well:

i just recently bought a 89 coupe with a DOHC KA24DE, and am getting horrible gas mileage, i replaced the O-ring on top of the fuel sending unit(?) and that seemed to have solved the horrible smell i got in the cabin.

I pulled the plugs and they are basically new, i am getting about 380km's(236miles) on one tank, with conservative driving (shifting at 2.5k). i was told the compression on the motor was:

1 - 1552- 1103- 1304- 155

upon adding abit of oil to the plug holes the numbers shot up a good 20-30psi, could shot piston rings be the source of my horrible gas mileage?

Also, after first getting the car, being excited of getting my first manual car, i took it to the redline a couple times(on empty highway suit: ), after the last time, i noticed that my temperature gauge was no where near the 1/2way mark that it should be, but just below the 1/4 mark, for the next week, the engine was taking for ever to warm up, and i had no heat. I then replaced the thermostat, this fixed it for awhile, then i tried it one more time, and it seems that the same problem has arisen.. anyone know why it would mess up the thermostat so quickly? thanks

EDIT: *240sx, refer to title

[5upra]

cyl. 2 is in terrible condition...with 3 not to far behind, and not good for gas mileage. Try flushing system and add new coolant.

[driftingmy240sx]

compression tests are not accurate you need to do a cylinder leak down test to check the rings. my 89 240 only ever got 220 miles to a tank. you have to remoember the ka24 is a truck motor in a 2 dr car. a tune-up may help with the gas mileage but not much.

[driftingmy240sx]

as for the coolant issue, sounds like you might have an air pocket.

[hoang]

as for the coolant issue, sounds like you might have an air pocket.

i am pretty sure i got all the air out? but before when it was working, when i would go above about 4k rpm the temp needle would go down pretty fast, and come back up after i let off.. i just tested the old thermostat that i took out and its working fine?