Corsica 95, 3.1L: EGR valve seems not activated
 

I am trying to figure out at what condition my Corsica 95, 3.1L, EGR valve starts activated. Valve has 3 solenoids and at park position I increase RPM to 2000 and using oscilloscope do not see any solenoid to be energized.
Currently trying to solve hi NOx problem, engine is after rebuild works
smooth.

So it won't pass emissions because of Nox?If so, what are the CO's in ppm? The egr might just need cleaned. The egr might come on with exhaust gas temp.

CO is equal to = 0, HC is equal to = 8 : NO is 1390 (three times bigger than limit) - this is at 1900RPM, Catalist is new: Magnaflow #93505 - Universal converter. Diagnostic data shows no engine errors at all.

I have figured out that it works only when car drives. EGR works but "NOx" is still high. Mechanic says engine can run lean - Can fuel injectors cause this?
Fuel pressure at injectors rail is around 35 psi

Well, nox, and co's are a function of temperature. I'd think if it were too lean, you have higher co's, and lower nox. However with the unburned hydrocarbon, interesting.

only 35 PSI?!
that fuel rail is supposed to have 40-45 PSI at least!!

We had an issue like this before, the car was getting extra gas because the pressure regulator ruptured and gas was going into the intake through the vacuum line...lol

Also low fuel pressure can cause it to run lean or wrong as well...

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So basically, it can be a number of things.
Please check in this order:

1) Check for defective fuel pressure regulator. Or replace to test and make sure its not the problem.
2) Check fuel pressure with engine off after running fuel pump a few times, pressure should go up to 40-45 PSI. (Check with both old and new pressure regulators.)
3)Check to make sure you do not have leaking or dirty injectors stuck "open."


It can either be one of 3 things:
1) Improperly functioning Pressure regulator.
2) Weak fuel pump.
3) Stuck open injector. (these need replaced, cleaning won't do anything).

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My 3.1L MPFI v6 reads 43 PSI average.
My 3100L SFI v6 reads about 44 PSI average.

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That EGR is actually 3 motors that open and close a plug.
Chances are it is working correctly.

But yah, that fuel pressure is low.
Does it have trouble at higher RPM's? sometimes low fuel pressure can cause this.

Also, inspect vacuum lines and check PCV valve for proper operation.

Please let me know what you find, or if you have other questions/comments. :)
Also, this is the same issue, try not to post other threads for this same vehicle & problem, it helps others with this issue and it also helps us help you.
And moderators do not like it, they get mad at that. lol :P

I have done the following:
1)replaced the fuel's pump motor (with -ACDELCO #EP313 - from RockAuto) - but not assembly
2)replaced fuel filter
3)replaced fuel regulator

When turn ignition ON (no crank) fuel pump starts work for couple of seconds and pressure rise maximum to 40-41 PSI. Pressure gauge is connected to injectors rail test port
When engine is run on idle the fuel pressure is around 35 PSI.
I think on idle the pressure cannot phisically be higher that 40PSI due to pressure regulator is rated for 40PSI
Also I put OBD2 catalitic convertor - please let me know if it is going to work on this type of car. This car has sticker with: EGR/HO2S/TWC/SFI
---TWC means that catalyst is three way
Please let me know how engine works in case of wrong timing.
As I understand it easy to see visually and listen
Currently looking for emission appointment, will let you know

Additionally to my previous:
1) each injector I have tested individually and cleaned with LUCAS inj cleaner an Gas (50/50% mixture under pressure)
2) after turn ignition ON (no crank) the gas ressure rise to 40-41Psi and stay for a lonf time - this means that all injectors are holding pressure - no stuck open case

hm...

You borderline on emissions or you failing miserably?


**(That still seems low to me for fuel pressure, but if thats how it is, I guess we can leave it...)**

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did you put a new catalytic or a used one?

Maybe the wrong kind of converter is installed, or its plugged up, maybe someone punched a hole in it?

However, there have been cases where some people installed a converter and it did not work properly on the given vehicle.

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I totally forgot this part:

Did you change the spark plugs?
Surprisingly bad plugs, cheap plugs, or improperly gaped plugs can cause this.

With the 3.1L MPFI engine you had better be using the AC delco (standard or platinum) single prong plugs with the proper gap, anything else is BAD with this engine.

If you do not have the proper plugs, get them out.
Especially Bosch plugs, they WILL warp the heads because they burn too darn hot, I learned the hard way 2 times with bosch plugs and warped heads.
And then I learned the hard way with cheap plugs before, they just do not work correctly.

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The last thing I can think of is disconnect that ECM for maybe 30 minutes, then see if there is a difference.
Those older EPROM block learning designs will learn, then their "learning" seems to get old after some time.

I usually reset mine before winter, then before summer simply because the drastic weather change really makes it confuzzled. lol

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Other than that, I'm simply lost.
Its hard to help sometimes with issues like this when the vehicle is not right in front of you...

EDIT: Maybe you got bad gas?
My old 2.8L v6 was borderline in emissions testing before, I had 5-6 gallons of gas, so I stuck 10 gallons or more worth of that alcohol based injector cleaner to help it pass, it worked for me, but it is not recommended. lol

Finally emission is fine. The summary is below:
1) replaced fuel filter, fuel regulator and fuel pump motor - after this fuel pressure at rail did not change too much: 40PSI when ignition is ON and 36PSI when engine is at idle run. Initially I suspected a poor gas supply/lean mixrure due to low pressure. It is easy to verify without replacing the above mentioned. There is return fuel line rubber hose under hood - so that when engine is in idle - just press it with pliers - and watch fuel pressure - if jumps over 40PSI - means that pump is performing well
2)Cleaned EGR, cleaned pipe from exhaust to EGR. Also cleaned passage from EGR flange to intake. Seems to me it was partially clogged
3) Replaced Catalytic converter with used OBD2, from Oldsmobile 2000, 3.5L, 200K milage. Put it close to exhaust. Looks like my previous universal Magnaflow 93505 was too far from exhaust flange
Did not touch sparks - but think to replace with original from dealer
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