i have an 88 GL with a 1.8 spfi my compresion is 110 in 1-3 and 105 in # 4 i have 299 thousand miles and wondering what a new engine should have thnx

any body know:banana:

might help to explain why you're checking. rarely do people check compression unless they have a reason too - what's going on?

 

that difference between the cylinders is no big deal. but i'm not sure what the SPFI is supposed to have. those numbers are really low for an MPFI so maybe they're different?

 

is the engine turning over fast...or slow and lugging (weak battery)?

compression will depend largely on RPM - the FSM even shows a graph of RPM verses compression ratio.

were the plugs all out and throttle propper open when cranking?

no the car runs great has ok power ican get 80 mph on the freeway and i had a good battery and i took the plugs out one at a time

the reason i wanted to know what new one should have is im putting a 4in lift

and 225/70/r16 on it soon and was wondering if rebuilding the motor would make a big enough diffrence to bother

r u supose to take all the plugs out when i do it maybe i did it rong thnx

ideally you take all the plugs out and prop the throttle plate open. otherwise, the engine has to work to compress all the cylinders (except the one you're testing or ones left out) and can't get any air - due to the throttle being closed. doesn't typically make a huge difference, but might make some.

 

you can search here or someone will eventually know what the SPFI compressions are.

ok thnx GROSSGARY ill try the comp check again see if it does any better:headbang:

and do a wet and dry test. That will tell us alot more too.

 

Right now those numbers show tired rings, but i think your numbers may be wrong, as the car should be down some power too.

 

nipper

"new/rebuilt" spec, according to the book, is something on the order of 160-175 psi IIRC, and "minimum spec" according to the FSM is something on the order of 120-140 psi.. BUT, I have heard many reports (including yourself) of perfectly adequate power and functionality all the way down to 100 PSI per cylinder. Your numbers SHOULD get bumped up a bit across the board by taking all four spark plugs out at once, disabling the fuel pump, propping the throttle wide open, and testing again.

 

but.. I can't imagine they will get bumped up too much.

 

Try the test again, and as nipper suggested, try a wet test afterwards and see what the numbers are. Remember, those specs are quoted for seal level, and a compression test is a very relative thing. "105 psi" is NOT inherently less than "115 psi" unless the two measurements are taken at the same time, by the same person, with the same gauge, on different cylinders.