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  #1  
Old 10-21-2004, 12:43 PM
possumfat9
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help with EGR vacuum control

My Svx of about 2 years now developed a problem. After I would first start car and temp gauge would start to move, engine would run very bad and create preasure on engine. It would clear up when temp reached normal. If you try to give it gas during the time it ran badly, it will skip stutter and blow oil. It will have no vacuum on air inlet and no preasure on exaust. Its as if the engine has no access to outside air. I assumed EGR problem. I have now removed intake and have tested most EGR and vacuum components. I removed EGR Vacuum control and noticed that hose are leading from intake to this valve is always leaking to atmosphere. I have taken this valve apart and it appears that it works this way. I just seems that this would always be a vacuum leak. Also if intake always draws air from this vacuum hose --dirt could get by the small filter in valve. I just need to know if this is proper operation of this valve> Thanks
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  #2  
Old 10-21-2004, 01:52 PM
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Are you getting any engine codes?

If you are experiencing crankcase pressure then your PCV valve may need replacing. Does your engine oil dipstick ever pop up?
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  #3  
Old 10-21-2004, 04:14 PM
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Yes, Dip stick pops out. Pcv valve has been replaced and is ok. This is strange problem because its like motor operates in closed envirament. Car cranks right up and runs good for about 3 minutes driving time. Then runs like crap and if I press gas petal to go faster than the 5 mph its going, it will spudder and blow oil everywhere. After gauge reaches normal operating temp all is fine except all the oil smpke from where it got all over exaust. I just would like to know how this egr vacuum control operates. Thanks
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  #4  
Old 10-21-2004, 05:21 PM
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  #5  
Old 10-21-2004, 05:32 PM
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My dipstick pops up.

I also happen to be tearing apart all my hoses at this very moment, and some of them just slide ight off without any effort.
Seems to be located in the same place I've been hearing a vacuum leak.
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  #6  
Old 10-21-2004, 06:15 PM
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Quote:
Originally posted by possumfat9
Yes, Dip stick pops out. Pcv valve has been replaced and is ok. This is strange problem because its like motor operates in closed envirament. Car cranks right up and runs good for about 3 minutes driving time. Then runs like crap and if I press gas petal to go faster than the 5 mph its going, it will spudder and blow oil everywhere. After gauge reaches normal operating temp all is fine except all the oil smpke from where it got all over exaust. I just would like to know how this egr vacuum control operates. Thanks
Hi Possum, the way the EGR is suppose to work is this. When the engine gets up to operating temp, the ECU opens the EGR solenoid valve, to allow exhaust gas to enter the inlet manifold to cool the combustion chamber down, to prevent the formation of oxides of Nitrogen in the exhaust gas.

There are three componets in the system. The EGR solenoid valve, the EGR valve, and the BPT valve. The ECU turns the system on when the operating temp is reached. The system is then controlled by the throttle butterfly position.

When the throttle valve is in the cruse position vacuum is applied to open the EGR valve to allow the recirculation of the exhaust gas to the inlet. This flow is modified by the BTP valve by bleeding the throttle vacuum away from the EGR valve to vary the amount of gas recirculated, in line with throttle position.

The things to note are, it should only operate when the engine is at operating temp and with the throttle in the cruse position.

Where is the oil coming from? You could try unplugging the EGR solenoid to see if the trouble goes away. If it does not, it is not the cause of the problem.

Harvey.
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  #7  
Old 10-21-2004, 07:20 PM
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Hey Harvey, people are worried about you...check the pray that our Aussie Friends are OK thread.

And glad you seem to be OK.

oh, and sorry for going O/T
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  #8  
Old 10-21-2004, 07:36 PM
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Originally posted by lee
Hey Harvey, people are worried about you...check the pray that our Aussie Friends are OK thread.

And glad you seem to be OK.

oh, and sorry for going O/T
Yes Lee just replied there. Thats a change, you worried about me in a storm from somebody that had the seasonal cyclones. Got your roof fixed yet?

Harvey
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  #9  
Old 10-21-2004, 09:12 PM
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Question

Quote:
Originally posted by oab_au


...the way the EGR is suppose to work is this. When the engine gets up to operating temp, the ECU opens the EGR solenoid valve, to allow exhaust gas to enter the inlet manifold to cool the combustion chamber down, to prevent the formation of oxides of Nitrogen in the exhaust gas.

Out of curiousity, how does recirculating the exhaust gas into the intake manifold cool the combustion chamber? Aren't the exhaust gasses really hot (to the tune of several hundred degrees Fahrenheight)?

- John
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  #10  
Old 10-21-2004, 10:08 PM
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Quote:
Originally posted by Red Wolf


Out of curiousity, how does recirculating the exhaust gas into the intake manifold cool the combustion chamber? Aren't the exhaust gasses really hot (to the tune of several hundred degrees Fahrenheight)?

- John
Yes it does seem strange, dont it.
But if you consider that this exhaust gas is inert, no oxygen, it is taking up space in the volume of air, that the cylinder inducted. This leads to less air to be burnt, so less heat in the chamber.

It only works at cruse, closes when the pedal is down.

Harvey.
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  #11  
Old 10-21-2004, 10:28 PM
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Re: help with EGR vacuum control

Quote:
Originally posted by possumfat9
My Svx of about 2 years now developed a problem. After I would first start car and temp gauge would start to move, engine would run very bad and create preasure on engine. It would clear up when temp reached normal. If you try to give it gas during the time it ran badly, it will skip stutter and blow oil. It will have no vacuum on air inlet and no preasure on exaust. Its as if the engine has no access to outside air. I assumed EGR problem. I have now removed intake and have tested most EGR and vacuum components. I removed EGR Vacuum control and noticed that hose are leading from intake to this valve is always leaking to atmosphere. I have taken this valve apart and it appears that it works this way. I just seems that this would always be a vacuum leak. Also if intake always draws air from this vacuum hose --dirt could get by the small filter in valve. I just need to know if this is proper operation of this valve> Thanks
Just thinking over breakie, From your discription, I think it is either the BTP valve, stuck closed, or it is not getting vacuum, to open it.

When the engine gets to temp, the ECU turns on the EGR Solenoid, this puts manifold vaccum on the EGR valve, to open the exhaust path. It then relies on the BTP Valve to bleed off vacuum to only allow the EGR to open when the throttle is in the cruse position. This is set by the drilling in the throttle bore that is opened and closed by the throttle plate position.

With this BTP valve not working, as soon as it reaches temp the exhaust path is opened, regardless of the throttle position, idle, full throttle, backed off,,,,,,,,,,,,,

This is the vacuum control valve that you have mentioned. Yes it is like a vacuum leak, except that the drilling is covered at idle by the throttle plate. It is this leak that bleeds off the vacuum to prevent the exhaust path from opening at the wrong time.

Harvey.
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Last edited by oab_au; 10-21-2004 at 10:31 PM.
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  #12  
Old 10-22-2004, 11:18 AM
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Re: Re: help with EGR vacuum control

Quote:
Originally posted by oab_au


Just thinking over breakie, From your discription, I think it is either the BTP valve, stuck closed, or it is not getting vacuum, to open it.

When the engine gets to temp, the ECU turns on the EGR Solenoid, this puts manifold vaccum on the EGR valve, to open the exhaust path. It then relies on the BTP Valve to bleed off vacuum to only allow the EGR to open when the throttle is in the cruse position. This is set by the drilling in the throttle bore that is opened and closed by the throttle plate position.

With this BTP valve not working, as soon as it reaches temp the exhaust path is opened, regardless of the throttle position, idle, full throttle, backed off,,,,,,,,,,,,,

This is the vacuum control valve that you have mentioned. Yes it is like a vacuum leak, except that the drilling is covered at idle by the throttle plate. It is this leak that bleeds off the vacuum to prevent the exhaust path from opening at the wrong time.

Harvey.
I allways thought Aussies spoke english??
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  #13  
Old 10-25-2004, 09:22 PM
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More like to allow vacuum to bleed off after the EGR control solenoid closes, otherwise the valve would remain open until manifold vacuum drops to nil (WOT or stall.)

Is it possible for the EGR to flow so much as to pressurize the crankcase? If it does it would be the first I've encountered. I would look for an errant chunk of catalyst that rolls around in the exhaust, blocking the flow to atmosphere. Whether or not that is still enough to cause excessive crankcase pressure is still difficult to believe. On certain engines with intake manifold crossover passages for carb heat a manifold burn-thru will cause such a situation but the SVX doesn't employ such a design.

Anyway, excessive EGR flow results in stalling - no O2, no combustion. Simple physics. The engine would stall before that much pressure could build.

One would then suspect a cracked piston or dysfunctional exhaust valves except the 'runs o.k. until warmed up'. An errant chunk of catalyst that eventually rolls around and plugs the exhaust would fit the bill excepting the crankcase pressure.

Sorry, no answer here. Too tired (and maybe already missed the point.) Will sleep on it and hopefully come back to find more information.

P.S. Good to see Harvey and Lee. My parents live a few miles south of Lee and spent a few weeks hiding out, up here with me. (Oh, joy.) heheheh Actually enjoyed their visit. And Lee, I owe you two. I had to sneak down last March for a family reunion and didn't have time to visit. I will keep trying.
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  #14  
Old 10-29-2004, 06:10 PM
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PLESE HELP! Still have problem but not what I thought!

Well, I appreciate all of the responses that I have received. I have now replaced all of the egr components and car still does the same. There is no subaru dealer anywhere near me. Last week I convinced a local service center to rent the software require from Snap-on to test my car.(strange that Subaru is not standard software with these analizers.) The problem has been determined but no reason found. It appears that after starting car that computer starts to retard timing. There should be certain default points in sytem but if so they are wrong. Anyway, computer retards timing until I am suffering from pre-detonation. (explains why dip stick blows out and crancase gets preasure-rised and oil goes everywhere.) I have studied the operation theary of this system and determined that Knock sensors were bad. I replaced them and new intake gaskets and it did no good. Now after talking to tech, we concluded must be computer malfunction.( high price article) I have noticed people here talking about resistor on Ebay. In theory it should make timing advance a small bit because of computer thinking air is colder than it actually is. I thought this would help test computer, so I bought one for 9 bucks. Instructions say to put resistor in place of Air temp sensor. I have studied eletric diagram and parts locator disc and see no such sensor. I e-mailed seller and he states that I should jump IAT Sensor in the mass air flow sensor. I have looked and still see no such thing. If anyone could please help me find the air temp sensor so that i can at least try this. If you notice I have posted only a few times and it always concerned this problem, as it has been going on about a year now. Again to explain problem.

I crank car and all is fine(runs good) As soon as temp hand starts to move car starts cutting out bad and back firing thru intake. If I press gas as to go faster than about 5 mph it skips and blows oil everywhere and exaust gets real hot and oil starts getting on it. smokes as if car is on fire. After engine reaches operating temp all is well again, its as if it never happened.(after oil is burnt off exaust that is) If I crank car and let it idle for 10 minutes it never has this problem. I love my SVX and have spent much time on it and really need to get this under control. Thanks to all.
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  #15  
Old 10-29-2004, 07:43 PM
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Knock sensors only retard the timing 8 or 12 degrees max, if I recall correctly. Plus retarding timing moves the engine AWAY from detonation, not towards. A slight, almost imperceptible loss of power results, most would notice a loss of fuel mileage before power loss as a result.

Have you tried disconnecting the coolant sensor (for the computer) and seeing what happens? Erratic behavior from the sensor could send the fuel management into a tailspin. The symptoms you describe sound more like that or the MAF is going wiggy. Does the oil smell like gas? Is the oil level mysteriously getting higher, as if oil has been added?
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