throttle body vacuum/boost leak?

[tronno]

back again for help.i searched the forums forever and never found any answers, so if anyone finds it somewhere,let me know.now for my problem, when i start my car in the morning,the car would idle rough and then stall.i replaced the vacume hoses and performed a boost leak but wont hold boost.i also replaced the o-ring on my biss screw.when i start my car i can hear a shhhhh sound from the intake manifold.when i put my ear on the intake manifold when the engine is running i can tell the sound is coming from the intake manifold.a week ago my car was fine now it runs like crap.today when i got in my car to go home from the mall the car was idleing terrible and i tried to drive it,hoping that if i had the gas in that i can drive home.well, i got the car in first and starting driving and the car would just drop its rpms and jump back up.i finally mashed on the gas and it went.when my engine got warm, my idle would become better(not stalling), but would still fluctuate from 400rpms to 1200rpms.i need help as soon as possible.its hard to drive to school with my car running like crap.so I'm open to any suggestions.thanks in advance

luyen

 

[tronno]

i forgot to add that my boost guage is showing 15 in vacuum

 

[girlieracr4g63]

TB seals, TB gasket, injectors..Just a few good places to start looking.


Wendy

 

[tronno]

TB seals, TB gasket, injectors..Just a few good places to start looking.


Wendy

when i did a boost leak test i didn't find any leaks on the tb seals and gaskets.i checked my injectors and the seem fine.i dont know what to do. i took a flashlight and checked my intake manifold gasket and the top part seems fine, but i havent checked the bottom part.i'm running out of ideas of what to do. i need some more suggestions on how to solve my problem.

 

[tom04841]

if you had a vacuum leak, the idle would be higher than normal. You are most likely running really rich and that is causing it to run like a$$. Problem seems to be before the tb. Double check all of your ic hoses. As far as the vacuum lines go.....eliminate them....they are unnecessary.

 

[kenamond]

You could also do a pressure test at your TB elbow instead of the compressor inlet. Divide and conquer. If you have TB/mani/injector/etc. leaks, fix them and move back to the compressor. Knowing what's *not* leaking can be helpful, because whatever's left is all that you need to look at.

I'm not sure of a good way to get soapy water at the lower side of the intake mani gasket, but a mirror and turkey baster with an extension hose stuck in the end might help (McGuyver!).

Could this be idle surge?

 

[tronno]

You could also do a pressure test at your TB elbow instead of the compressor inlet.QUOTE]

i did and it wont hold any boost .i hear air coming out of my valve cover breather .is that normal or where am i leaking if its coming out of their?

 

[kenamond]

i did and it wont hold any boost .i hear air coming out of my valve cover breather .is that normal or where am i leaking if its coming out of their?

Hmm. You might want to check your PCV valve (coming off the back-left side of your valve cover when standing in front of the car). It's supposed to be one-way *out* of the valve cover and into the intake manifold. If it's bad, you may be pumping boosted air into your valve cover through the PCV. You might want to search to see how a PCV typically fails. You could probably pull the PCV out of the valve cover, plug the hole in the valve cover with your finger and have someone pressurize your system again. If air comes out your PCV and stops coming out of your breather hose, then the PCV is bad.

It might also be due to really poor compression. That's the only other way I can think of for air to get into the valve cover (past the rings and back through the oil return passages into the valve cover. You could find this out by doing a compression test.

Oh, and I guess it could also be leaking intake valve seals, too.

 

[tronno]

Hmm. You might want to check your PCV valve (coming off the back-left side of your valve cover when standing in front of the car). It's supposed to be one-way *out* of the valve cover and into the intake manifold. If it's bad, you may be pumping boosted air into your valve cover through the PCV. You might want to search to see how a PCV typically fails. You could probably pull the PCV out of the valve cover, plug the hole in the valve cover with your finger and have someone pressurize your system again. If air comes out your PCV and stops coming out of your breather hose, then the PCV is bad.

It might also be due to really poor compression. That's the only other way I can think of for air to get into the valve cover (past the rings and back through the oil return passages into the valve cover. You could find this out by doing a compression test.

Oh, and I guess it could also be leaking intake valve seals, too.

air was going past the pcv valve,so i replaced it. I did a boost leak test from the tb elbow.i used an air compressor and pressurized the intake and got boost to build up to 17lbs but then looses pressure in about 7seconds.i blocked off the pcv valve and pressurized my intake again and heard air comming out from underneath the valve cover. I also heard a leak comming from one of the vacume lines,so i started the car with everything put back on and sealed the vacume line leak with my finger and the idle is still the same.i think it might be bad compression. I'm getting a compression tester on saterday. O yea i went to autozone because my check engine light was on and got the code p0172,so im running rich.i need some help fast.what causes bad compression anyways. I've been looking for a solution for over a month so any help and suggestions would be great.thanks

 

[kenamond]

air was going past the pcv valve,so i replaced it. I did a boost leak test from the tb elbow.i used an air compressor and pressurized the intake and got boost to build up to 17lbs but then looses pressure in about 7seconds.i blocked off the pcv valve and pressurized my intake again and heard air comming out from underneath the valve cover. I also heard a leak comming from one of the vacume lines,so i started the car with everything put back on and sealed the vacume line leak with my finger and the idle is still the same.i think it might be bad compression. I'm getting a compression tester on saterday. O yea i went to autozone because my check engine light was on and got the code p0172,so im running rich.i need some help fast.what causes bad compression anyways. I've been looking for a solution for over a month so any help and suggestions would be great.thanks

Did you check that the new PCV was not leaking? Did you get an OEM valve or an Autozone/Carquest valve? The Autozone/Carquest valves won't work; they aren't designed for boost pressures. The OEM valve is about $4 at a mitsu dealership. I went through 2 valves that didn't work out of the box: one from Autozone and one from Carquest.

Did you spray everything down with soapy water? Make sure you check your injector insulators (between injectors and head). Get a flashlight and stick your head up over the fuel rail so you can see where to spray and where to look for bubbles when you pressurize it.

You'll lose compression from worn piston rings, crud on your valve seats, worn valve seats, and worn valve guides. A compression test will tell you if you have good or low compression, but a leakdown test will tell you which part is leaking.

Did you repeat the test on the TB elbow or on the compressor inlet when you dropped 17psi in 7sec?

 

[tronno]

Did you repeat the test on the TB elbow or on the compressor inlet when you dropped 17psi in 7sec?[/QUOTE

i repeated the test on the tb elbow.i will do a leakdown test on saterday.and maybe buy some stuff to clean my combustion chamber

 

[kenamond]

Did you repeat the test on the TB elbow or on the compressor inlet when you dropped 17psi in 7sec?[/QUOTE

i repeated the test on the tb elbow.i will do a leakdown test on saterday.and maybe buy some stuff to clean my combustion chamber

Did you put in an OEM PCV valve or an Autozone/Carquest/other valve? Did you test it before you put it in (blow/suck through it...it's one-way OUT of the VC (air shouldn't be able to go through the PCV valve and into the VC *at all*).

Do a compression test first. If you have good compression, there's no reason to do a leakdown test. And if you have good compression, then I'd still suspect the PCV valve.

Also, if your motor came to a halt at the wrong crank angle, you might have the valves in atleast one cyclinders overlapping (both intake/exhaust open at same time) which would leak your boost leak test pressures right out the exhaust. You can disable the ignition and turn the car over a small amount if this is the case. It's pretty rare, so having the motor stop there twice in a row would be very unlikely.

Let me know where you got that PCV valve.

 

[tronno]

Let me know where you got that PCV valve.

i got the pcv valve at advance auto parts.can you give me the part number for the valve so i can get it a mitsubishi.thanks

 

[kenamond]

i got the pcv valve at advance auto parts.can you give me the part number for the valve so i can get it a mitsubishi.thanks

Sorry. I don't know. Try calling your local mitsu dealership, get the parts department, and ask them for a 99 eclipse GSX PCV valve. Of course you can use any year of a 1g or 2g and any turbo model, but 99 GSX will do just fine. I didn't need a part number to pick mine up. I just walked back to the parts desk and asked them for one.

Before you leave there with it, open the bag and blow on the end where the hose connects (not the copper tube/threaded end). If it leaks, ask for another or don't buy it.

 

[tronno]

i did a compression test and here are the numbers
1-175
2-175
3-180
4-160

could this cause my car to run like crap?

 

[tronno]

a while after i did my first compression test, i took my car out for a drive around the block and as i started driveing down the street i heard a banging sound from the engine bay.as i turned around to head back to see what happend, i heard a banging sound again.when i got home, i poped my hood and checked if anythings wrong.i found nothing.i reved my engine and when i reached about 3k rpms i can hear a banging sound around cyl #1.as i rev the engine even past 3k rpms, the sound got faster and louder.i turned my car off and i checked my oil level because there was a bunch of oil coming out of the oil cap as i reved.the dipstick was showing no oil.i drove my car in the garage and let it sit for a minute and checked the oil level.and still no oil on the dipstick.i checked underneath the oil cap and their was smoke coming out of the valve cover from the cap(i guess its because low oil in there). i did another three compression tests and these are the results

1-170
2-175
3-170
4-145

1-170
2-175
3-170
4-149

i added a little bit of oil in each cylinder and got these numbers:

1-173
2-180
3-176
4-155

my questions:
what could that sound be coming from?
could the low oil cause the engine to make this sound?
why is their oil coming out of the oil cap instead of breather hole?
my compression test results shows that the valves may be the cause of low compression.am i right?

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[tronno]

update: i just started my car and my idle is at like 300rpms.i tried to drive the car down the street and when i pressed in the clutch, my car stalled.i started it back up and drove back to my house. i reved my engine a little bit(quickly reved to about 1000rpms and it stalls.can someone help or give me some suggestions. i am desperate to get my car running like normal.

 

[kenamond]

Sorry it took so long for me to reply. I was on vacation last week.

You shouldn't have a difference of more than 15psi between any two cylinders in your compression test. 178 is perfect, and 133 is the minimum you should have.

You say you hear a sound from #1, but your compression numbers look great for 1,2,3 but low for #4. Just to make sure, #1 is on the driver's side, and #4 is on the passenger side.

You shouldn't drive your car with low oil levels. Did you notice low oil pressure on the gauge?

If you're sure the oil is leaking from the oil cap, get a new one. You might be able to replace the sealing gasket for cheaper, but I'm not certain. I know I've seen OEM caps at either SBR or ExtremePSI.

A compression test won't tell you what's leaking (rings, valve seals/guides). A leakdown test will. You might want to have a leakdown test done on your bad cylinder (what you're calling #4). Call around and find a shop that does leakdown tests. Many shops mistake this for a compression test. A leakdown test requires an air compressor and a two-gauge instrument to diagnose what is leaking and how badly. Also, they don't turn the motor over with the starter motor. Anyway, tell them that it's the test with the compressor. There is a good site describing both types of tests, but I'm swamped by kids at the moment and don't have time to search.

I'd also suggest posting a new thread regarding this new problem. I'm not an expert on this new problem - I was trying to help with your boost leaks .

 

[tronno]

Sorry it took so long for me to reply. I was on vacation last week.

You shouldn't have a difference of more than 15psi between any two cylinders in your compression test. 178 is perfect, and 133 is the minimum you should have.

You say you hear a sound from #1, but your compression numbers look great for 1,2,3 but low for #4. Just to make sure, #1 is on the driver's side, and #4 is on the passenger side.

You shouldn't drive your car with low oil levels. Did you notice low oil pressure on the gauge?

If you're sure the oil is leaking from the oil cap, get a new one. You might be able to replace the sealing gasket for cheaper, but I'm not certain. I know I've seen OEM caps at either SBR or ExtremePSI.

A compression test won't tell you what's leaking (rings, valve seals/guides). A leakdown test will. You might want to have a leakdown test done on your bad cylinder (what you're calling #4). Call around and find a shop that does leakdown tests. Many shops mistake this for a compression test. A leakdown test requires an air compressor and a two-gauge instrument to diagnose what is leaking and how badly. Also, they don't turn the motor over with the starter motor. Anyway, tell them that it's the test with the compressor. There is a good site describing both types of tests, but I'm swamped by kids at the moment and don't have time to search.

I'd also suggest posting a new thread regarding this new problem. I'm not an expert on this new problem - I was trying to help with your boost leaks .

i understand that cyl #4 is on the passenger side.im guessing the sound was coming from the valvetrain because of the low oil.i pulled the head out and i found out that my #4 cylinder has some pretty scratched up walls and some beat up pistons from when a piece of spark plug feel into it.my other cylinders arnt as bad but they do have minor scratches on the walls.im going to bring my block to a mechine shop so they can do a .02 overbore on all of my cylinders.then im going to buy new pistons with a .02 oversize.i will probably have to get a valvejob done.i should have done a leakdown before i took off the head. is their anyway i can see if my valves are bad after i took off the head. my valves arnt burnt but they are built up carbon from running rich for a long long time.oh yea, can i just replace my valves and valve seal or do i have to get my head mechined for the valves to fit correctly?btw thanks for the reply

 

[kenamond]

i understand that cyl #4 is on the passenger side.im guessing the sound was coming from the valvetrain because of the low oil.i pulled the head out and i found out that my #4 cylinder has some pretty scratched up walls and some beat up pistons from when a piece of spark plug feel into it.my other cylinders arnt as bad but they do have minor scratches on the walls.im going to bring my block to a mechine shop so they can do a .02 overbore on all of my cylinders.then im going to buy new pistons with a .02 oversize.i will probably have to get a valvejob done.i should have done a leakdown before i took off the head. is their anyway i can see if my valves are bad after i took off the head. my valves arnt burnt but they are built up carbon from running rich for a long long time.oh yea, can i just replace my valves and valve seal or do i have to get my head mechined for the valves to fit correctly?btw thanks for the reply

If you had leaks due to deposits on the valve seals, I believe that the seafoam treatment will clean up deposits - do a search on seafoam for more info.

Aside from that, I don't feel qualified to tell you much more. I'd do some searching with regards to each of the questions you have and post a new thread with your current situation for whatever you can't answer via searching.

Sorry and good luck.