did a compression test today
03-01-05, 07:32 PM
#1
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did a compression test today
I was with a friend so I could finally do one. Keep in mind that I have never done one on my car.
A little history.
-Bought the car in the summer for 1700cndn. Came with the mods you see below in my sig, and he told me that it had a brand new engine on it. He wasn't lying, there were TII housings installed so defenitly a rebuild had been done. Recently, **** if I know?
Engine misses occasionaly, very slight but noticable. Idle can't be controlled it seems at all, and there was white smoke recently pouring out of my exhaust on a cold day, and still noticable on a hot day like today.
I checked the filler cap for bubbles in the coolant, indicating blown coolant seals, and there were non while the engine was running. Honestly, Im not sure how in the hell that test was even concieved as the coolant doesn't flow very much at all in there, and yes I have a good waterpump. Maybe I should have waited for the engine to warm up with the cap off? i don't know.
ANYWAYS
Pulled out the leading front plug, snugged in the comp tester plugged and hooked it up. Friend turned her over while I held in the gauge release button and she bounced like this
85-90-85
Around there, couldn't tell exactly. Every time it bounced I could here air coming out of the button that I was pressing, I think that gave me an inaccurate reading! So I left the button in, and it bounced as high as 105 wich I was pleased with. So one rotor face has good compression, and if the above numbers are accurate its not looking good.
Hooked up the rear leading, got my friend to turn her over while I was holding in the button, heres what I got
70-65-65
LMAO, man this thing is fucked up. Again I could here air leaking out of the button that I was pressing, so im still not sure if thats accurate. If It is, this will explain the missing and just overall shitty idle.
So in retaliation, I broke out the TB cleaner, its got a lubricant in it, and I was running premix anyways so im sure this was totally safe. Fed the tip into the atomization vacuum line and gave her a high rev and started pumping. I shot half the can in there and it was running real rough, but I held on. Let it off and it seemed to run slightly smoother, missing was less frequent. Reved it up again and shot the rest of the can in there, took about 5 minutes of squrting but after she was done it was pretty smooth. A miss here and there, but better than before.
Anyways im posting this for some advice here. Did I do the check right? I mean air leaking out of the release button doesn't throw off the accuracy of the numbers? how should I handle this?
Im waiting for the engine to cool down a bit before I go out and do it again, so throw up some advice for good ol brent. thx guys!~
A little history.
-Bought the car in the summer for 1700cndn. Came with the mods you see below in my sig, and he told me that it had a brand new engine on it. He wasn't lying, there were TII housings installed so defenitly a rebuild had been done. Recently, **** if I know?
Engine misses occasionaly, very slight but noticable. Idle can't be controlled it seems at all, and there was white smoke recently pouring out of my exhaust on a cold day, and still noticable on a hot day like today.
I checked the filler cap for bubbles in the coolant, indicating blown coolant seals, and there were non while the engine was running. Honestly, Im not sure how in the hell that test was even concieved as the coolant doesn't flow very much at all in there, and yes I have a good waterpump. Maybe I should have waited for the engine to warm up with the cap off? i don't know.
ANYWAYS
Pulled out the leading front plug, snugged in the comp tester plugged and hooked it up. Friend turned her over while I held in the gauge release button and she bounced like this
85-90-85
Around there, couldn't tell exactly. Every time it bounced I could here air coming out of the button that I was pressing, I think that gave me an inaccurate reading! So I left the button in, and it bounced as high as 105 wich I was pleased with. So one rotor face has good compression, and if the above numbers are accurate its not looking good.
Hooked up the rear leading, got my friend to turn her over while I was holding in the button, heres what I got
70-65-65
LMAO, man this thing is fucked up. Again I could here air leaking out of the button that I was pressing, so im still not sure if thats accurate. If It is, this will explain the missing and just overall shitty idle.
So in retaliation, I broke out the TB cleaner, its got a lubricant in it, and I was running premix anyways so im sure this was totally safe. Fed the tip into the atomization vacuum line and gave her a high rev and started pumping. I shot half the can in there and it was running real rough, but I held on. Let it off and it seemed to run slightly smoother, missing was less frequent. Reved it up again and shot the rest of the can in there, took about 5 minutes of squrting but after she was done it was pretty smooth. A miss here and there, but better than before.
Anyways im posting this for some advice here. Did I do the check right? I mean air leaking out of the release button doesn't throw off the accuracy of the numbers? how should I handle this?
Im waiting for the engine to cool down a bit before I go out and do it again, so throw up some advice for good ol brent. thx guys!~
03-01-05, 07:44 PM
#2
usually you should remove the schrader valve completely from the tester for accurate results. be sure the battery is fully charged and probably even have a jumper installed for more cranking amps to turn the engine over quicker. hold the throttle wide open while doing the test also.
some people say this test is innacurate with some guages and i would tend to agree, i would only take the test seriously for a comparison between both rotors, yours being that much of a difference from front to rear indicates that there is a problem and could be the cause of the rough idle and idling issues.
some people say this test is innacurate with some guages and i would tend to agree, i would only take the test seriously for a comparison between both rotors, yours being that much of a difference from front to rear indicates that there is a problem and could be the cause of the rough idle and idling issues.
03-01-05, 08:48 PM
#3
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How do you remove the valve? I'll take a look at it now and see if I can figure it out.
Thx for the tips btw, had no idea, well at least wasn't thinking, that a full battery, WOT and a jumpered harness would make a difference. I'll try those out and post some numbers.
For the tester, now that im looking at it. I don't think I want to remove the check valve, but I want to remove the hold valve thats near the end of the hose. It traps air inside the tube, to hold the PSI meter so that you can check it after you get out of the car (1 man job). If you hold the valve in on the end of the hose (The one that connects to the spark plug hole) then you can blow air both ways through the tube. If I remove this, then it will read every face right? and not just hold the PSI of the first face?
let me know.
Thx for the tips btw, had no idea, well at least wasn't thinking, that a full battery, WOT and a jumpered harness would make a difference. I'll try those out and post some numbers.
For the tester, now that im looking at it. I don't think I want to remove the check valve, but I want to remove the hold valve thats near the end of the hose. It traps air inside the tube, to hold the PSI meter so that you can check it after you get out of the car (1 man job). If you hold the valve in on the end of the hose (The one that connects to the spark plug hole) then you can blow air both ways through the tube. If I remove this, then it will read every face right? and not just hold the PSI of the first face?
let me know.
03-01-05, 09:14 PM
#4
you want the air to escape near the guage, what you are checking is the bounces not the max pressure(with the valve installed).
it is the same as a tire inflator valve in your wheels, you just need a schrader valve removal tool which you can pick up at a auto parts store for around a buck or more.
it is the same as a tire inflator valve in your wheels, you just need a schrader valve removal tool which you can pick up at a auto parts store for around a buck or more.
03-01-05, 10:23 PM
#7
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Results are in.
I took your advice, told my dad to give er WOT and I removed the valve with a screwdriver.
Engine was cold
Front
-100-100-100
Rear
-90-90-90
Wierd. I did run a whole can of TB cleaner through the engine earlier to see if any carbon would get the hell out, looks like it worked sort of. Now that I've done the test right, im really not sure if the compression has changed at all since the last numbers weren't accurate.
Im still burning coolant, I can see it out of the exhaust. Its still missing occasionaly, so I think that could be the result of the coolant in the combustion chamber making it hard to fire..
One thing thats driving me nutz is that I start it with the clutch in, and let it out immediatly, it stalls. If I hold the clutch in, it will run for about 10 seconds at 1000rpm and then sputter down and stall. If I give it throttle for 2 minutes or so, keeping the rpm at 2k, then I can let the clutch out and everything and she'll hold on her own.
The BAC is installed, thats whats driving me nutz. Somethings fucked, I have no idea what. But with my emissions removed theres really not much left to check on this ******* car.
thanks for any help/suggestions.
I took your advice, told my dad to give er WOT and I removed the valve with a screwdriver.
Engine was cold
Front
-100-100-100
Rear
-90-90-90
Wierd. I did run a whole can of TB cleaner through the engine earlier to see if any carbon would get the hell out, looks like it worked sort of. Now that I've done the test right, im really not sure if the compression has changed at all since the last numbers weren't accurate.
Im still burning coolant, I can see it out of the exhaust. Its still missing occasionaly, so I think that could be the result of the coolant in the combustion chamber making it hard to fire..
One thing thats driving me nutz is that I start it with the clutch in, and let it out immediatly, it stalls. If I hold the clutch in, it will run for about 10 seconds at 1000rpm and then sputter down and stall. If I give it throttle for 2 minutes or so, keeping the rpm at 2k, then I can let the clutch out and everything and she'll hold on her own.
The BAC is installed, thats whats driving me nutz. Somethings fucked, I have no idea what. But with my emissions removed theres really not much left to check on this ******* car.
thanks for any help/suggestions.
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03-01-05, 10:36 PM
#8
numbers look alright but if there is coolant going through the motor then that's obviously not good..
if you do not have an AWS then it will need to warm up before it will idle on it's own, nature of the beast. mine does the same thing, i have to feather the throttle on startup and hold the idle for at least a minute before it can hold on it's own. i rebuilt my engine 1k miles ago and it has always done this.
if you do not have an AWS then it will need to warm up before it will idle on it's own, nature of the beast. mine does the same thing, i have to feather the throttle on startup and hold the idle for at least a minute before it can hold on it's own. i rebuilt my engine 1k miles ago and it has always done this.
03-01-05, 10:51 PM
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Oh, I used this stuff called intake medic. I shot it through the fuel atomizer vac line like described above, seemed to work nicely
Its made by gunk, called intake medic. cleans-protects-lubricates thats what it says on the side. It says its safe for catalatic converters and o2 sensors for those still running their cats.
Its made by gunk, called intake medic. cleans-protects-lubricates thats what it says on the side. It says its safe for catalatic converters and o2 sensors for those still running their cats.
03-01-05, 11:41 PM
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there's actually a guy who posted couple of weeks ago datalogits of compression testing when the engine was cold or hot, with WOT or not
the best results were for a cold engine with WOT ( around 10 to 15 PSI more than hot
When I brought my car to the mazda dealer they took it with my warmed up engine, and it ended like 105PSI front and 95PSI rear...
add the 10-15 psi when cold and its not really far away from the factory numbers
anyway, some people say to test it hot, some say to test it cold...
up to you man...
the best results were for a cold engine with WOT ( around 10 to 15 PSI more than hot
When I brought my car to the mazda dealer they took it with my warmed up engine, and it ended like 105PSI front and 95PSI rear...
add the 10-15 psi when cold and its not really far away from the factory numbers
anyway, some people say to test it hot, some say to test it cold...
up to you man...
03-01-05, 11:42 PM
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It doesnt matter. Cause if those are the numbers for cold, then hot will be even better. Im happy with what I got, im just confused still with idle issues and the coolant ****. I can see it coming out of the exhaust, but I never have to fill up coolant. I don't drive the car tho.. lol, I just let it idle.
Im going to try a coolant compression test. If it doesn't hold stock PSI and theres no coolant leaking on the ground, then I can for sure figure that its the seals. Any other ideas?
thx
Im going to try a coolant compression test. If it doesn't hold stock PSI and theres no coolant leaking on the ground, then I can for sure figure that its the seals. Any other ideas?
thx
03-01-05, 11:46 PM
#16
Passing life by
Just a couple quick notes depending on your tester.
Most guage testers have 2 schrader valves one in the end and one on the other end of the house. the one on the guage end relives the presure in the house. leave this one in. the next one is in the bottum your tester should be threded in the end. you can remove this valve as said with a schrader valve remover $5 or use a small screw driver and unscrew it. Make sure you screw your compreshion tester into the spark plug hole. some testers are not threded and u just push a ruber taperd end into the hole. yea this test is a lil more inauret then a electronic rotor tester thingy magiger but hey who has one of thow :-/
and im sure you know to remove the EGI fuse when doing this
Most guage testers have 2 schrader valves one in the end and one on the other end of the house. the one on the guage end relives the presure in the house. leave this one in. the next one is in the bottum your tester should be threded in the end. you can remove this valve as said with a schrader valve remover $5 or use a small screw driver and unscrew it. Make sure you screw your compreshion tester into the spark plug hole. some testers are not threded and u just push a ruber taperd end into the hole. yea this test is a lil more inauret then a electronic rotor tester thingy magiger but hey who has one of thow :-/
and im sure you know to remove the EGI fuse when doing this
03-01-05, 11:53 PM
#18
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If compression was higher during cold, then we would have no cold starting issues, and people wouldn't have to plug in their cars. Heating the block in the winter is usefull for only one thing, getting good compression.
Yea I got the valve thing right, it was at the end of the hose. I just screwed it out as it was threaded in there like karack said.
Yea I got the valve thing right, it was at the end of the hose. I just screwed it out as it was threaded in there like karack said.
03-02-05, 12:25 AM
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You know thats what I was thinking a while back. Until I had the car ideling for like 30 minutes and the white smoke was still just as strong as before.
I think the only way im going to solve this dumb *** mystery is with a coolant pressure tester. I can't think of anything else. Also, why is it missing every few seconds? its not compression, its not the timing, it has to be coolant leaking in there causing the AFR to not ignite.
thx for your replys btw! Its nice to see people throwing in their bit of info.
I think the only way im going to solve this dumb *** mystery is with a coolant pressure tester. I can't think of anything else. Also, why is it missing every few seconds? its not compression, its not the timing, it has to be coolant leaking in there causing the AFR to not ignite.
thx for your replys btw! Its nice to see people throwing in their bit of info.
03-02-05, 12:28 AM
#22
depends on climate and relative humidity, if the exhaust system never fully warms up the condensation won't go away. the idle issue could be any of a number of things: faulty secondary ignition cables, worn plugs, semi plugged fuel filter, clogged or dirty injectors, faulty sensors, misadjusted variable resistor, the list goes on...
03-02-05, 12:31 AM
#23
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Well to narrow down that list I have cleaned/replaced the following
-plug wires
-plugs (NGKS)
-Injectors (cruzin)
My variable resistor is shot, if I unplug it, it makes no difference, if I leave it plugged in and turn the screw, it makes no difference.
I should replace the fuel filter tho, i've never done that. I should also get a working VR. I should also make a code checker too, find out easy if any of the sensors are fucked.
thx for your advice.
-plug wires
-plugs (NGKS)
-Injectors (cruzin)
My variable resistor is shot, if I unplug it, it makes no difference, if I leave it plugged in and turn the screw, it makes no difference.
I should replace the fuel filter tho, i've never done that. I should also get a working VR. I should also make a code checker too, find out easy if any of the sensors are fucked.
thx for your advice.
03-02-05, 03:19 AM
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Surprised no one mentioned... if you're just idling and there is an internal coolant leak... that's bad.... you're not putting a lot of pressure on the water pump so water isn't getting pushed around very much... you could have air pockets inside the engine that aren't getting out to the radiator.
Turning on the heater full blast and then revving the engine (assuming it's you know, in good condition enough for you to rev it) up really high... or just revving it slowly all the way through to 7k (maybe 1-2 seconds per 1k rpms) should get things moving... whether the car is on a downhill/uphill incline will also effect this.
I know because I've been dealing with coolant leaks for the last few weeks... the buzzer doesn't even bother me anymore... it's when you hear the buzzer then it turns off you should worry... means air hit it, then went away... could've gone back into the engine.
--Gary
Turning on the heater full blast and then revving the engine (assuming it's you know, in good condition enough for you to rev it) up really high... or just revving it slowly all the way through to 7k (maybe 1-2 seconds per 1k rpms) should get things moving... whether the car is on a downhill/uphill incline will also effect this.
I know because I've been dealing with coolant leaks for the last few weeks... the buzzer doesn't even bother me anymore... it's when you hear the buzzer then it turns off you should worry... means air hit it, then went away... could've gone back into the engine.
--Gary