Compression Test Results...Not Good

[BadMojo]

Just had my '93 240SX @ Nissan to get some lifters replaced. I had a compression test done just for the hell of it, and was not at all pleased with the results.

I didn't get all the details, but the cylinders range from 112-118 PSI.

The service guy seemed to think this was perfectly acceptable on a "high mileage engine". My car only has 97K on it...I've seen 130K KA's with much, much better compression results.

So...where to go from here? It's not like the KA24DE has a ton of power on tap to start with, and I've got even less. I don't really have the funds for an SR swap, and it doesn't seem worth it to pay big $$$ to try to get the engine rebuilt.

Does this just sound like normal wear on rings or cylinder walls? The previous owner must have beat the piss out of my poor car.

Apologies for the rambling post...not particularly happy now.

[U12 2NR]

did he have the throttle full open when he tested the car? those numbers are really low. I unsure of it would be able to run alright with low numbers like that, seems fishy. Since your motor has quite a bit of miles on it, it doesn't have to only be piston rings, it could also be carbon build up on the valves, so a compression test would show low if your valves are fully closing...do a leak down test.

Anyway, if the numbers are true, and you know the engine's days are numbered, take it as easy as you can on it. In the meantime, scrape up every cent you can get your hands on and when you have enough money then you'll have a range of options. You could install a used engine, rebuild your engine, do a swap, buy another car.

[BadMojo]

Anyway, if the numbers are true, and you know the engine's days are numbered, take it as easy as you can on it. In the meantime, scrape up every cent you can get your hands on and when you have enough money then you'll have a range of options. You could install a used engine, rebuild your engine, do a swap, buy another car.

I'll probably just drive it until it blows. It needs front struts and rotors, but I can do those pretty cheap.

I'm tired of messing around with this thing. I'd sell it, except I'd never get anything close to what I put in to it. Eventually it will make a nice chassis for someone to swap an SR in to.

[Titan]

Ewww... that does not sound normal at all.

If I recall correctly, that is below the "minimum compression" as stated in the FSM.

My motor has 105k miles on her, and she tested out at 155-160 across the board.

Then again, I have a KA24E... so my compression is a little higher stock.

Do you smoke blue or white on startup?

[BadMojo]

Ewww... that does not sound normal at all.

If I recall correctly, that is below the "minimum compression" as stated in the FSM.

My motor has 105k miles on her, and she tested out at 155-160 across the board.

Then again, I have a KA24E... so my compression is a little higher stock.

Do you smoke blue or white on startup?

No smoke. Minimum on a KA24DE is 155 PSI, I believe.

[DAEDALUS]

I'll ask the same question: Did the tech hold the throttle plate wide open? Also, were all the plugs out and the injectors shut off? The fact that they all lie in such a tight range is a good sign. Usually cylinders that fall that much don't fall together. Is there any reason to believe the compression would be that low? Whenever a CT falls low like that, it's always expected to repeat the test with a teaspoon of oil in each cylinder, to verify if it is indeed the rings that are bad.

[BadMojo]

I'll ask the same question: Did the tech hold the throttle plate wide open? Also, were all the plugs out and the injectors shut off? The fact that they all lie in such a tight range is a good sign.

I'll have to talk to the service manager tomorrow. I can't believe they wouldn't know how to do a proper compression test, but...

Usually cylinders that fall that much don't fall together. Is there any reason to believe the compression would be that low? Whenever a CT falls low like that, it's always expected to repeat the test with a teaspoon of oil in each cylinder, to verify if it is indeed the rings that are bad. [/QUOTE]

The car was running fine with the exception of a bit of lifter noise. Lifters were replaced, engine flushed and refilled with GTX 10w40. As far as I know, I didn't have any smoke or power problems (although I have nothing to compare it to).

I was too surprised and depressed at the time to ask questions.

[:: orion ::]

My motor has 105k miles on her, and she tested out at 155-160 across the board.

Then again, I have a KA24E... so my compression is a little higher stock...

Huh...?

SOHC KA24Es had either 9.1:1 or 8.6:1...

All the DOHC KA24DEs had 9.5:1...

- - - - - - - - - - - -

But I'd suspect a bad test - Buy a tester for $20 and re-test yourself. Engine fully warm, all plugs pulled, throttle open, battery at full charge.

Good luck - Brian

[BadMojo]

The real numbers are actually:

#1 = 118#2 = 120#3 = 120#4 = 122

I don't know what the guy who told me 112-118 was looking at.

The car still drives well and doesn't smoke. I know someone who will do the compression test for free for me, so I'll try again to confirm.

I will most likely drive it until I see visible symptoms of a failing engine. As I thought of it, it's really not that expensive to get a lower mileage KA and transmission installed since so many folks are doing SR swaps. I can swing $1000-1500 if it nets me an engine and transmission with half my current miles on it.

My ultimate plans are to try to go with a KA-T, so I'll most likely drive this engine in to the ground while I work on my brakes and suspension. I'll go shopping for a healthier KA later down the road.

I was freakin' out a bit yesterday.

[98talon]

Try that Engine Restore stuff that they sell at parts stores. Normally I stay away from snake oils, but I tried this one on a whim. The compression on my talon went from 150-150-90-150 to 185-185-183-185. It's worth a try anyway.

[U12 2NR]

from 90 to 183?

i'm officially declaring myself a disbeliever.

badmojo, the engine doesn't pour out smoke when you let put the pedal to the floor and take off? Also, if you take off your oil cap, do you feel alot of air gushing out?

[BadMojo]

badmojo, the engine doesn't pour out smoke when you let put the pedal to the floor and take off? Also, if you take off your oil cap, do you feel alot of air gushing out?

No symptoms of a blown head gasket, if that's what you're asking about. I'm not going to worry about the low compression (though I will check it again) until driveability starts to suffer. My distant plans are to go with a KA-T, so I will most likely drive this KA until it self-destructs and then swap in a fresh, healthy one.

I'm still a little skeptical about the #'s since the car seems fine. If I lost any power, I haven't noticed it. Of course, since my last car was a Ford Tempo, almost anything is an increase in power (I bought the 240 in October).

[lbrowne]

I get smoke when I first start the car and then rev her pretty good. Once shes been running for short while I don't get the smoke anymore.

I'm just gunna drive her till she dies.

[Thee 240sx Owner]

I get on my 89 240 (KA24E) with 160k on it 147 -155 across all 4.. theres something seroiusly going on there with yours man..

[240driver39]

my 122k 91 ka-de had 180psi across the board when i tested it at 112k. straight from teh fsm it states min is 151psi and the standard is 179 psi

The guy must had done the test wrong or something, those numbers are too low to be happening without u noticing a problem...i would do the test myself, its easy and testors are cheap.

also if there is another 240 in the area, try drivin that, see what the butt dyno says, i live near quakertown and would be willing to help u out

[lbrowne]

RacinDa240sx: this is off topic, but is that the stock red for your 240sx? Do you have more pictures? I'm probably going to paint my 240sx coupe red, I'm looking for a deep rich red.

thanks,

lbrowne

[+ve psi]

Hey guys, this is my first post. Been browsing the forums for a little while now, seems like a very knowledgable bunch

Last week I bought a 1990 240sx with 139k km (86.3k miles) and have have just done a compression test. My numbers where exactly the same as BadMojo's (120 psi) however i did the test with the fuel pump and injectors still on and without wide open throttle. Could straying from the proper procedure give me those low results?

Also, can anyone help me out with a link on how to change valve seals. When the car is idling at in the morning or at a long red light i get a puff of blue out the back.

Thanks very much

[DAEDALUS]

Not doing it right will give you lower readings. 40psi is a big difference though. If your compression's low and you're burning oil, it suggests your rings are bad, and maybe not the valves/guides/seals.

[+ve psi]

Thanks for the reply, i re-did the compression test with the proper procedure and found a 150 psi even on all cylinders. That seems a little better

[Dattebayo]

what is the proper procedure for a compression test? Ive got 85K on my DE and i am now a little more than curious.

[+ve psi]

From another site :

Measurement of Compression Pressure

1. Warm up engine.2. Turn ignition switch off.3. Release fuel pressure (See How to Change Fuel Filter)4. Remove all spark plugs.5. Disconnect distributor center cable.6. Attach a compression tester to No. 1 cylinder.7. Depress accelerator pedal fully to keep throttle valve wide open.8. Crank engine and record highest gauge indication.9. Repeat the measurement on each cylinder as shown above.Note: Always use a fully charged battery to obtain specific engine revolution.

Compression Pressure kPa (kg/cm2, psi) / RPMStandard = 1,236 (12.6, 179) / 300Minimum = 1,040 (10.6, 151) / 300Difference limit between cylinders = 98 (1.0, 14) / 300

10. If cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinders through the spark plug hole and re-test compression.

* If adding oil helps compression, piston rings may be worn or damaged. If so, replace piston rings after checking piston.

* If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat.

* If compression in any two adjacent cylinders is low and if oil does not help compression, there is a leak past the gasket surface. If so, replace cylinder head gasket.

[BadMojo]

Still haven't had a chance to re-check my compression. It's possible the techs at the dealership just messed up the test (which is hard to believe), but I think that's probably a long shot.

I'll let you guys know what the results are this weekend (not sure if anyone cares, but it would give some closure to this thread.)

[Altiman94]

Get a leakdown test, it's the only really sure-fire way to test your actually compression. Alot of altima guys over on altimas.net do that before they go the nitrous route

[BadMojo]

A leakdown test will tell me where the problem lies, but as long as the compression test tells me I've got poor compression across all four cylinders, there really isn't much to do, IMO.

I can get a KA cheaper than any sort of rebuild could cost. As far as I can tell, it's pretty much a buyer's market for KA engines right now.

I'm still waiting on the compression test. My fiance hasn't been feeling well lately, so I haven't had a chance to do the compression test myself. Maybe next weekend...

[D-UNIT]

[QUOTE]Originally posted by :: orion :: "]Huh...?

SOHC KA24Es had either 9.1:1 or 8.6:1...

All the DOHC KA24DEs had 9.5:1...

- - - - - - - - - - - -How do you test compression ratio. I have a chiltons manual that says the 91' de motor has a compression ratio of 8.6:1, 92+ de's have a higher cr. Also, instead of pulling the fuel pump fuse and releasing the fuel pressure, can't you just disconnect the injectors and the ignition coil's ground wire. Same result, but ten times faster.

[Thee 240sx Owner]

RacinDa240sx: this is off topic, but is that the stock red for your 240sx? Do you have more pictures? I'm probably going to paint my 240sx coupe red, I'm looking for a deep rich red.

thanks,

lbrowne

Sorry for not responding quicker.. Ya that is the stock red that came with the car...

[drift-sx]

i made a very stupid comment and now this is to cover it up becuase i don't knwo how to remove a post