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Boost leak test, air coming from cylinder

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Jeff99GS

15+ Year Contributor
1,870
15
Jun 27, 2006
Cleveland, Ohio
I was doing a boost leak test on my 99 eclipse 420a turbo, and I had the Spark Plugs out to gap them. All of the air I was pushing into the turbo inlet was coming right out of my
3rd Cylinder hole. Is this just because my engine may have been shut off and that intake valve was open?? Or is this something more major? Should I do a compression test?

:dsm: :laser:
 
Its probabally on the intake stroke and the valve is open,you could crank it over a little and try again.Put the other 3 plugs in and crank it till air comes out of the 3 hole while cranking it which would mean its on its way to TDC on the compression stroke(both valves closed) then do a boost leak test and see if air still leaks from that cylinder.
 
Thanks guys, I figured it was just an open intake valve but I just got scared at first when I Heard air coming out of the spark plug hole. :rolleyes:
I just got back from Summit Racing cause I had to buy MSD blaster ignition coil for my car, cause my stocker just went bad on me. My question is are these things any diffrent than the stock unit? I would have just got the OEM one but NO one had it in stock. It was $140 from Satan :barf:
 
Okay I ran my car and it seems to run great, But when I did a compression check I had

#1 #2 #3 #4
180lbs 179lbs 169lbs 179lbs

Is my compression too low in cylinder #3?
Can anyone tell me if these numbers are normal?
 
you should be ok. Not sure with the 420a engines but I beleave the 4g63's are suppost to be within 15lbs or so. Usually when they start to get off like that, its a sign of a head gasket. If I were you, I would not worry about it just yet.
 
The only reason I am asking about the compression is cause the car seems to miss fire when the engine is decelerating. I just replaced my coil, wires and the plugs are about 2 months old. I boost leak tested it and did the comp test but I can not figure out why its doing this. Could my Injectors be bad?? If i was to get new injectors are the accell ones OK? what size is the best for a turbo 420a? Modern Performance has 21lb/ 24lb/ 30lb/ 36lb
are any of those good?
 
Jeff99GS said:
The only reason I am asking about the compression is cause the car seems to miss fire when the engine is decelerating. I just replaced my coil, wires and the plugs are about 2 months old. I boost leak tested it and did the comp test but I can not figure out why its doing this. Could my Injectors be bad?? If i was to get new injectors are the accell ones OK? what size is the best for a turbo 420a? Modern Performance has 21lb/ 24lb/ 30lb/ 36lb
are any of those good?

Whoa whoa whoa killer slow down a minute. DOn't jump to on the injectors yet, I cannot see how that would cause this issue.

That misfire you hear can EASILY be mistaken for backfire. Backfire is from unburned feul entering the combustion chamber. This is normal for boost cars. I can actually spit fireballs with my car, as my buddy can with his STi also.

As far as the air leak and compression goes, of anything it sounds like a ring issue. If you've got damage to the ring lands, sometimes you'll see oil jump up past the ring(because of the damage)DRENCHING plugs to the point that they stumble so bad it's almost impossible to have idle or smooth acceleration. True story. We just found this on my buddies Glanat the other day. This may explain your 'misfire' sound..

But then again, it could also be more damage to cylinder #3 tthan any other. I find it interesting that the low # cyclinder (compression) is also the same one allowing air to escape under pressure.

I'd have someone do a leak down test to check the ring lands at this point. Change the plugs, drive it for 30 minutes, then check them again. Look at the plug on cylinder #3...
 
[it could also be more damage to cylinder #3 tthan any other. I find it interesting that the low # cyclinder (compression) is also the same one allowing air to escape under pressure.

I'd have someone do a leak down test to check the ring lands at this point. Change the plugs, drive it for 30 minutes, then check them again. Look at the plug on cylinder #3...[/QUOTE]


Well thats what I thought.... but the spark plug out of cylinder #3 looks EXactly the same as the rest. very clean, tan light brown electrode they look perfect to me. I think I'm just not explaining my symtoms right. If I WOT the car it runs excelent but if I try to creep with slight gas pedaling it kinda sounds like its missing and will even surge a little. I had a bad MAP sensor last week and It wouldn't even stay running when that was bad. so I changed it and it seemd ok till I just put on my 60mm throttle body, but I don't think thats the problem either cause i have no vaccum or boost leaks.
The only reason I suspect the injectors is cause I had an injector go bad on me a few years ago....and I just change the 1 that was bad cause I was broke at the time. I figure the other 3 injectors can't be far behind. I'd rather be safe than sorry.
So anyway the today the car started missing real bad the other day and the CEL was flashing, so I checked it with my scan tool and it said that cylider #1 AND #2 were missing and the coil bank A was bad. So I bought a new coil and all my CEL's went away but it still feels funny when I try to creep or decelerate. what else could it be??

If the injector was failing couldn't that make it miss fire aswell from NO fuel?

Whats the best size and brand injector to get?
 
The best injector for a 12:1 fmu is the stocker 19lbs you could MAYBE get away with one size larger injectors(21lb) think you said.S-FMU and Accel 30lbs would be the best imho.

edit: Also i beleive the cylinders are supposed to be within 10% of each other try squirting a little bit of oil in the low #3cylinder,if the compression rises then its probabally the rings.But you should be good.
 
What do I need to make a S-fmu? is that like a megasquirt? Do you think the injectors could be causing the miss? why am I not getting a CEL? Is it cause I didnt drive it enough since I reset the codes?
 
S-FMU is a super fuel management unit,you can change out the discs and springs inside to get close to what you need for fuel.Then you can adjust your static and idle pressure from there.You need 4an fuel line to the rail(you mount the sfmu under the hood unlike the fmu in the rear if youve got the late fuel system.)The feed goes to the test port on the fuel rail. Remove the schrader valve then u need a 4an or 6an return line to your tank.Im not sure about injectors causing a misfire you may try running some injector cleaner through them and my evap CEL takes at least 30miles to come back on so id wait and see what it does.Hope this helps. Brian

edit:S-FMU is nothing like megasquirt its simply a rising rate FPR.Megasquirt is standalone engine management system.I beleive most people use Aeromotive 1:1 fpr's for megasquirt.
 
Does it misfire when revving it and holding it at a constant rpm (like 2k or so)?
 
No.. It doesn't miss when I rev it or when I hold it. I just drove it and it seems better now? Maybe it was just coughing out the extra fuel in cylinder #1 and #2 I just changed the ignition coil cause I had a major miss fire in #1 and #2 and my scaner said the coil was bad.
Now It almost feels like when I first apply the gas while accelerating it kinda stutters almost like fuelcut but not so severe. its like the car acts funny till the boost and FMU kick in?? then its smoother. The engine seems to idle great and run great but when I go to leave from a stop it stutters. Could it be the 60mm throttle body? I just put that on a week ago.
 
Jeff99GS said:
Now It almost feels like when I first apply the gas while accelerating it kinda stutters almost like fuelcut but not so severe. its like the car acts funny till the boost and FMU kick in?? then its smoother.

It's hard to tell you what this could be. Honestly, it takes time for the vacuum to raise feul pressure under boost. That's why when you stomp the gas, it may hesitate or sputter a second, because it takes time for everything to work simotaneously. But then if you ease into boost, it'll smooth out and feel great...

WHat size are you vaccuum lines?
I don't see how any of you think this is feul related... :|

[/QUOTE]The engine seems to idle great and run great but when I go to leave from a stop it stutters. [/QUOTE]

Don't drop the clutch too quick, and/or just give it more gas! :p
 
Do you feel like its a slugish response when you tap the gas? Try check the Throttle cable adjustment and make sure its nice and snug but that your throttle plate doesn't open.

My throtle is real touchy even with the 60mm TB
 
totaleclipse_05 said:
Does it misfire when revving it and holding it at a constant rpm (like 2k or so)?


Yes it does seem like it is doing that now. when I rev it and hold it at 2k it kinda stutters around but I can't tell if its a miss or someting else. Overall the car seems to run/idle good and it doesn't do this stutter at idle....only when I rev/hold, decelerate or if i'm just driving along and not accelerating, just trying to maintain a constant speed
What the hell could this be? I have a new MAP new IAC new IGN COIL new WIRES Fairly new PLUGS new 60mmTB. Sould I put new plugs in it? I think I have a bad rear O2 sensor could that be the problem? Could my front O2 sensor be going bad? I think its too close to the turbo exhaust outlet :notgood: Any Ideas?
 
Well Its NOT missing... its more like a surging?? If I try to creep it at about 10mph it surges like someone is throttling it....could this be a bad FPR or FMU? If I revv it up around 2k rpm it surges like that too....floating up and down slightly in the RPMs
I have been driving it and I still have NO CEL's at all. The only reason I suspect the FPR or FMU is because I tried to go WOT and it felt slow and was lean so I
backed off it....:notgood: I have a Stock FPR with 120,000 miles and a used Vortech FMU

Anybody Got Ideas?
 
[QUOTE Hmm idk but i like your upper intake,its purty.[/QUOTE]

Haha thanks! Its just the stocker but I grinded it smooth and polished it.

Has anyone had a FPR go bad on them? If so what are the symptoms?

Does my engine just need a rebuild?

Is my compression low?
180- 179- 165- 179

That seems low for a stock N/T
 
Your compression is normal. The cylinders cannot be more that 10%-15% variance.

Your popping on decel is raw fuel igniting in the exhaust. Blitz is very wrong, its not normal, it is a lack of tuning. Last i checked ALL fuel entering the combustion chamber is unburnt. The correct statement would be, unburnt fuel LEAVING the combustion chamber.

When you let off the gas, the ECU cuts 100% fuel. If fuel is still entering the combustion chamber, you have an injector leak. Test the injectors for leaks. Depending on your setup, the process will vary.

Now you could be running so rich that raw fuel is accumulating in the exhaust and on decel it is ignitied.

If you dont have a wideband, its time to get one. Also check your cam timing. Late timing will cause this as well.

Ok looked at your setup, hope its up to date. Nitrous kits.....Fuel solinoids are known for leaking when they fail.


TO TEST FOR INJECTOR LEAKS (STOCK FUEL RAIL)

Tools:
Fuel pressure gauge
Pliers
Jumper wire

Concept: The Idea is to pressurize the fuel rail and clamp off the feed line to force the fuel rail to hold pressure. If pressure holds until you release the feedline then you have 4 injectors that are fully closing.

Proceedure:
1. Unhook your Nitrous system from the test port on the fuel rail and connect the fuel pressure gauge. Make sure you can see the pressure gauge while working in the engine bay.

2. Disconnect the fuel pump relay.

3. Use the jumper wire to jumper the relay plug to power up the fuel pump.
_____a. when looking at the fuel pump relay plug, the rear most and front most pins are the 2 you will jumper together.

4. When you hear the fuel pump power up, you will notice the fuel pressure gauge rasies to appx 50psi. Soem might be lower, dont be alarmed.

5. With a pair of pliers, reach under the intake pipe and fully pinch off the rubber fuel feed line to the fuel rail.

6. While holding the pliers tight and pinching off the fuel line, remove the jumper from the fuel pump relay, this shuts the pump down.

7. Notice the fuel gauge, note the fuel pressure. The pressure should remain constant and not drop off.

If the pressure drops off, repeat the test to make sure you are fully pinching off the fuel line. If you are and you are still seeing the pressure drop inside the rail then you have a leaking injector.


Paul feel free to post this in a Writeup fashion for future reference.

Terry
 
Your compression is normal. The cylinders cannot be more that 10%-15% variance.

Your popping on decel is raw fuel igniting in the exhaust. Blitz is very wrong, its not normal, it is a lack of tuning. Last i checked ALL fuel entering the combustion chamber is unburnt. The correct statement would be, unburnt fuel LEAVING the combustion chamber.

When you let off the gas, the ECU cuts 100% fuel. If fuel is still entering the combustion chamber, you have an injector leak. Test the injectors for leaks. Depending on your setup, the process will vary.

Now you could be running so rich that raw fuel is accumulating in the exhaust and on decel it is ignitied.

If you dont have a wideband, its time to get one. Also check your cam timing. Late timing will cause this as well.

Ok looked at your setup, hope its up to date. Nitrous kits.....Fuel solinoids are known for leaking when they fail.


TO TEST FOR INJECTOR LEAKS (STOCK FUEL RAIL)

Tools:
Fuel pressure gauge
Pliers
Jumper wire

Concept: The Idea is to pressurize the fuel rail and clamp off the feed line to force the fuel rail to hold pressure. If pressure holds until you release the feedline then you have 4 injectors that are fully closing.

Proceedure:
1. Unhook your Nitrous system from the test port on the fuel rail and connect the fuel pressure gauge. Make sure you can see the pressure gauge while working in the engine bay.

2. Disconnect the fuel pump relay.

3. Use the jumper wire to jumper the relay plug to power up the fuel pump.
_____a. when looking at the fuel pump relay plug, the rear most and front most pins are the 2 you will jumper together.

4. When you hear the fuel pump power up, you will notice the fuel pressure gauge rasies to appx 50psi. Soem might be lower, dont be alarmed.

5. With a pair of pliers, reach under the intake pipe and fully pinch off the rubber fuel feed line to the fuel rail.

6. While holding the pliers tight and pinching off the fuel line, remove the jumper from the fuel pump relay, this shuts the pump down.

7. Notice the fuel gauge, note the fuel pressure. The pressure should remain constant and not drop off.

If the pressure drops off, repeat the test to make sure you are fully pinching off the fuel line. If you are and you are still seeing the pressure drop inside the rail then you have a leaking injector.


Paul feel free to post this in a Writeup fashion for future reference.

Terry

Working on an FAQ as we speak... this'll definitely be there.

Good to see you on Tuners again, by the way. It's always a pleasure.
 
Thanks Talon ESI-T, that sounds like a great Idea! I will test it out today at work and let you know what I find out. A leaking Fuel injector makes sense cause it won't do it if i'm 1/2 throttle. I am definatly getting new injectors anyway....cause mine are old and I already had 1 go bad last year. I'm gunna check my fuel solinoid on the Nitrous setup too Thanks for the help man!
 
Okay I did the fuel injector leakage test, my Fuel Pres was 54psi...is that too high? I then used some vise grips to pinch off the fuel line and disconnect the fuel pump jumper, and the Fuel pressure slowly droped to 30ish psi. So does that mean I need new injectors?
if so what should I get?
 
54 is ok.

Your saying it dropped slowly to 30 psi and held fine? That sounds like pressure leaking at the vise grips. When pinched off tightly so no fuel can squeeze past, the pressure should not drop at all. Did you retest a couple times to make sure the test results were consistant?

If you know for a fact you are pinching off the feed line tightly and there is no way fuel can be getting passed the vise grips, you have a leaker.


To be 100% positive (since the pressure drop is questionable), unbolt the rail and pop it out of the manifold. Leave it connected to the fuel system. now jumper the fuel pump relay again. You should not see fuel leaking from the injector tip.

You can do this without taking the manifold apart. the bolts are 13mm. just remove the coil for clearance.
 
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