What should engine compression be

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Not so sure how to do that I think my numbers are showing a old engine but I think it's still in spec truck has 340k miles

 

[Fix4Dirt]

Not so sure how to do that I think my numbers are showing a old engine but I think it's still in spec truck has 340k miles

in response to what? fuel trims? or compression? sorry a bit confused

 

[RADIOACTIVE_TOOL_SHED___]

in response to what? fuel trims? or compression? sorry a bit confused

For compression 120 is pretty low but isn't that in spec? But 120 and 140 worry me with a 20 PSI difference

 

[Fix4Dirt]

For compression 120 is pretty low but isn't that in spec? But 120 and 140 worry me with a 20 PSI difference

ya want at LEAST 100, thats the bare minimum. heres a thread with some results from another member. How to: - Compression test and specs rule of thumb is 10% difference, 10% of 140 is 14, 140-14=126. so slightly below the 10% rule. however i am not too sure. the numbers in that thread seem much higher than 120. i think thats an ohv too cause North has one according to this thread Need compression specs also maniak had mentioned his wa 160

 

[Josh P]

Elevation will change the compression readings. I realize NC isn't very high in elevation. If you have access to an air compressor, get a leak down tester. It uses compressed air, usually regulated at 100 psi. The drop in air pressure over a minute is calculated as a % of loss. A fancy unit will have a gauge that shows it on the display.

 

[RADIOACTIVE_TOOL_SHED___]

ya want at LEAST 100, thats the bare minimum. heres a thread with some results from another member. How to: - Compression test and specs rule of thumb is 10% difference, 10% of 140 is 14, 140-14=126. so slightly below the 10% rule. however i am not too sure. the numbers in that thread seem much higher than 120. i think thats an ohv too cause North has one according to this thread Need compression specs also maniak had mentioned his wa 160

Stupid question but what exactly does the whole 75 percent within the highest reading cylinder mean? Is mine in spec with that being the lowest is 120 and highest is 140

 

[Fix4Dirt]

Stupid question but what exactly does the whole 75 percent within the highest reading cylinder mean? Is mine in spec with that being the lowest is 120 and highest is 140

the percentage differences, sucg as 10% which isbwaht i use, not sure ive heard 25% before gives you indication that there could be an issue with that specific cylinder thats low. low compression in 1 cyl can indicate some damage such as worn rings due to ingesting something broken rod, bad vslve list goes on, and it shows that one cylinder has more damage than the rest. within 10% is alright to account for natural differences as time goes on. not sure if that made too much sense. essentially it helps isolate tjat there is an issue with a cylinder which then means you need to diagnose further into that cylinder and what couldve damaged it.

with your 25% rule yes its within the difference. with the 10% rule i use then no its out of the difference. iirc theres no factory spec, so i woudlnt call it a spec. rule of thumb is compression must must mustbbe above 90-100 to run. usually i see numbers in the 160 and above so ya 140 and 120 aint stellar either

heres a example of info a conpression test can turn up for you. im doubtful its this severe but you get the gist of it. let me know if that didnt make sense

 

[RADIOACTIVE_TOOL_SHED___]

the percentage differences, sucg as 10% which isbwaht i use, not sure ive heard 25% before gives you indication that there could be an issue with that specific cylinder thats low. low compression in 1 cyl can indicate some damage such as worn rings due to ingesting something broken rod, bad vslve list goes on, and it shows that one cylinder has more damage than the rest. within 10% is alright to account for natural differences as time goes on. not sure if that made too much sense. essentially it helps isolate tjat there is an issue with a cylinder which then means you need to diagnose further into that cylinder and what couldve damaged it.

with your 25% rule yes its within the difference. with the 10% rule i use then no its out of the difference. iirc theres no factory spec, so i woudlnt call it a spec. rule of thumb is compression must must mustbbe above 90-100 to run. usually i see numbers in the 160 and above so ya 140 and 120 aint stellar either

heres a example of info a conpression test can turn up for you. im doubtful its this severe but you get the gist of it. let me know if that didnt make sense

Yes it makes sense now, motor is just worn I think my fault and the previous owners fault for running it with vaccum leaks, remain seal is leaking on it as well the 10% percent rule is the most common and probably most accurate I'm going to voltage drop test the battery cables and the coil pack and ICM connectors to completely rule out spark, then if that ain't it guess I'll be shelling out big bucks for a engine rebuild, motor that's in it now has almost 400k miles

 

[Fix4Dirt]

Yes it makes sense now, motor is just worn I think my fault and the previous owners fault for running it with vaccum leaks, remain seal is leaking on it as well the 10% percent rule is the most common and probably most accurate I'm going to voltage drop test the battery cables and the coil pack and ICM connectors to completely rule out spark, then if that ain't it guess I'll be shelling out big bucks for a engine rebuild, motor that's in it now has almost 400k miles

sheeesh at 400 thats a run i wouldnt complain about! i still got strong compression at 330, and if mine were to deop tomorrow i wouldnt even be mad. dissapointed, but gave er a real good run. and i mean stuff just wears out over time at 400k it aint a new motor by any means lets see if others have dufferent wisdom however

 

[Josh P]

If the motor has to come out, one with 2 more cylinders should go back in.

 

[RADIOACTIVE_TOOL_SHED___]

sheeesh at 400 thats a run i wouldnt complain about! i still got strong compression at 330, and if mine were to deop tomorrow i wouldnt even be mad. dissapointed, but gave er a real good run. and i mean stuff just wears out over time at 400k it aint a new motor by any means lets see if others have dufferent wisdom however

If the motor has to come out, one with 2 more cylinders should go back in.

I've thought about a 5.0 just seems like alot of work 4.0 is a good engine just slow

 

[410Fortune]

FOR THE CYLINDER WITH The 120 psi do this
Run the compression test again, should come up 120
Now add a capful of engine oil to the cylinder, directly through the plug hole and run it again
Did compression go up? if so it is the piston rings that are worn
If not then it is likely valve or valve seat leaks
I would still run it, you can get it to run smoothly with 120 psi still in that cylinder

Your ignition wires are suspect, do not replace them with part store cheapo's
Have you tried cleaning the MAS?

 

[RADIOACTIVE_TOOL_SHED___]

FOR THE CYLINDER WITH The 120 psi do this
Run the compression test again, should come up 120
Now add a capful of engine oil to the cylinder, directly through the plug hole and run it again
Did compression go up? if so it is the piston rings that are worn
If not then it is likely valve or valve seat leaks
I would still run it, you can get it to run smoothly with 120 psi still in that cylinder

Your ignition wires are suspect, do not replace them with part store cheapo's
Have you tried cleaning the MAS?

It's got a new maf and plug wires, I hooked up a vacuum gauge to it today and it is fluctuating at idle speed I can't seem to figure out if Sligh fluctuations are OK It's reading between 20 and 21 here's a video of it,

 

[Fix4Dirt]

It's got a new maf and plug wires, I hooked up a vacuum gauge to it today and it is fluctuating at idle speed I can't seem to figure out if Sligh fluctuations are OK It's reading between 20 and 21 here's a video of it,

aint no video showin up

 

[RADIOACTIVE_TOOL_SHED___]

It's got a new maf and plug wires, I hooked up a vacuum gauge to it today and it is fluctuating at idle speed I can't seem to figure out if Sligh fluctuations are OK It's reading between 20 and 21 here's a video of it,

It's got a new maf and plug wires, I hooked up a vacuum gauge to it today and it is fluctuating at idle speed I can't seem to figure out if Sligh fluctuations are OK It's reading between 20 and 21 here's a video of it,

aint no video showin up

I know I'm trying to upload it to YouTube and then post a link here, is any fluctuations at all acceptable on a vacuum gauge?

 

[Fix4Dirt]

I know I'm trying to upload it to YouTube and then post a link here, is any fluctuations at all acceptable on a vacuum gauge?

10-4 just checkin ya onew it wasnt showin up on my end!

Quick Tech: How to Read a Vacuum Gauge to Pinpoint Engine Problems

A vacuum gauge is an invaluable resource for tracking down engine issues. The key is understanding what your gauge is trying to tell you. We’ve put together this quick-guide to …

www.onallcylinders.com

 

[RADIOACTIVE_TOOL_SHED___]

10-4 just checkin ya onew it wasnt showin up on my end!

Quick Tech: How to Read a Vacuum Gauge to Pinpoint Engine Problems

A vacuum gauge is an invaluable resource for tracking down engine issues. The key is understanding what your gauge is trying to tell you. We’ve put together this quick-guide to …

www.onallcylinders.com

Yeah it's looking more and more ignition related I'm thinking hopefully wellp I'll order a inline spark tester and get to work mabey I have a bad ignition switch module or something of that nature my plugs wires coil and icm are new so bad ground ignition switch, or wiring cats are not plugged no vaccum leaks good fuel pressure decent compression good computer and good functioning sensors thank you guys for the help and happy 4th of July! I'll report back when I do some spark testing

 

[Fix4Dirt]

Yeah it's looking more and more ignition related I'm thinking hopefully wellp I'll order a inline spark tester and get to work mabey I have a bad ignition switch module or something of that nature my plugs wires coil and icm are new so bad ground ignition switch, or wiring cats are not plugged no vaccum leaks good fuel pressure decent compression good computer and good functioning sensors thank you guys for the help and happy 4th of July! I'll report back when I do some spark testing

Happy 4th!!!! let us know how it goes! cleanin up the X and other vehicle today, been doin it for hours now... wash... clay, prep, wax, vacuum clean protectant then windows then engine time almost done with the X and subaru onto the honda next waiting for wax to cure... gonna be worth it, then some burgers on the grill!

 

[RADIOACTIVE_TOOL_SHED___]

I

Happy 4th!!!! let us know how it goes! cleanin up the X and other vehicle today, been doin it for hours now... wash... clay, prep, wax, vacuum clean protectant then windows then engine time almost done with the X and subaru onto the honda next waiting for wax to cure... gonna be worth it, then some burgers on the grill!

can't wait to get my truck painted and have the interior redone when I'm done figuring out this rough idle should have my tester Thursday wish I would have taken my time to throughly diagnose things before instead of throwing parts at it now I'm broke lol

 

[Fix4Dirt]

I

can't wait to get my truck painted and have the interior redone when I'm done figuring out this rough idle should have my tester Thursday wish I would have taken my time to throughly diagnose things before instead of throwing parts at it now I'm broke lol

lol aint we all ahhh man insurance and gas prices... really got me there... ahhh man st least we never have the cash to get into no big trouble, wspecially at my age no matter how much we want to cant afford the stuff!

want to see it all redone though, keep us posted on that!