Could a EGR cause low Vac?

Weasy2k · 12-02-2006, 05:05 PM

Ok so i am still working on this 5S (Project PAIN in my ass

)

There is an odd problem im having here that i need some help figuring out:

1) When i turn the engine over the car will start very fast...and die right off the bat...

2) When giving it a bit of gas then turning it on the engine will run but stumble like its miss firing. As soon as gas is let off then engine stumbles then dies.

3) I hooked up a Vac gauge to one of the spare ports on the intake mani and did #2 again which showed a vac reading of -5 in hg goign no lower then -10in-hg..

4) Doing the above test methods and having the MAP sensor unplugged would result in the engine trying to maintain an idle for a bit longer as well as having less of a miss fire.

I have:
-Checked Compression COLD 195 205 205 205
-Checked spark All good
-Checked Engine timing (did this when engine was out and checked several times over)
-Checked Dist Timing to the cam
-Played with engine timing with same results.
-Fuel pump chugges away no problem

Now i am thinking that it has to do with vacuum because the MAP sensor is reading low vac which usualy means more fuel so the engine runs REALLY rich and billows smoke out.

I have the TB taped shut and am using a leak down tester to blow air into CYL 1 with the intake valves open to let air into the intake manifold....yes there are leaks everywhere but im building 2-3psi in the manifold in hopes to hear where most of the air is going.

Any ideas? Gah this is really annoying me! First 5s job...and it sucks...3s's nmever gave me this issue.

EDIT:
I have located some air leaking by the EGR coming from inside the diaphram....im going to remove it and continue the pressure test...i wonder if thats it...
Thanks guys!~

Jason.MZW20 · 12-02-2006, 06:26 PM

The EGR VSV and vacuum modulator should produce no vacuum at 2500rpm with the coolant temperature below 131 F. They should produce low vacuum above 140 F. This is with TE1 and E1 shorted.

If vacuum is being applied to the EGR valve somehow, the engine will run rough or die. A large amount of exhaust gas will cause your engine to misfire a bit.

Check your vacuum line connections.

Weasy2k · 12-02-2006, 06:28 PM

HA perfect thats the info i needed. (I dislike these things)
This also explains why the engine runs better when giving it gas...

Weasy2k · 12-02-2006, 07:16 PM

Still no go...i changed the EGR and replaced teh gasket again (have spares) to make sure its fine....

@Q$#) i pressurized the manifold itself without the egr and TB and it built up pressure with no noticable air leak....

12-02-2006, 05:05 PM	#1 (permalink)
Weasy2k 3.4L 10K RPM In the works Join Date: Mar 2005 Location: Vancouver, BC Posts: 8,886 Thanks: 34 Thanked 76 Times in 65 Posts iTrader Rating: (6/100% )	Could a EGR cause low Vac? Ok so i am still working on this 5S (Project PAIN in my ass ) There is an odd problem im having here that i need some help figuring out: 1) When i turn the engine over the car will start very fast...and die right off the bat... 2) When giving it a bit of gas then turning it on the engine will run but stumble like its miss firing. As soon as gas is let off then engine stumbles then dies. 3) I hooked up a Vac gauge to one of the spare ports on the intake mani and did #2 again which showed a vac reading of -5 in hg goign no lower then -10in-hg.. 4) Doing the above test methods and having the MAP sensor unplugged would result in the engine trying to maintain an idle for a bit longer as well as having less of a miss fire. I have: -Checked Compression COLD 195 205 205 205 -Checked spark All good -Checked Engine timing (did this when engine was out and checked several times over) -Checked Dist Timing to the cam -Played with engine timing with same results. -Fuel pump chugges away no problem Now i am thinking that it has to do with vacuum because the MAP sensor is reading low vac which usualy means more fuel so the engine runs REALLY rich and billows smoke out. I have the TB taped shut and am using a leak down tester to blow air into CYL 1 with the intake valves open to let air into the intake manifold....yes there are leaks everywhere but im building 2-3psi in the manifold in hopes to hear where most of the air is going. Any ideas? Gah this is really annoying me! First 5s job...and it sucks...3s's nmever gave me this issue. EDIT: I have located some air leaking by the EGR coming from inside the diaphram....im going to remove it and continue the pressure test...i wonder if thats it... Thanks guys!~ __________________ -Johnny @ Sea2Sky Tuning - www.sea2skytuning.com http://www.mr2.com/forums/sea2sky-tu...-out-sale.html

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12-02-2006, 06:26 PM	#2 (permalink)
Jason.MZW20 Torque Me!!! Join Date: Jul 2006 Location: Victorville, CA Posts: 691 Thanks: 9 Thanked 51 Times in 44 Posts Blog Entries: 5 iTrader Rating: (1/100% )	The EGR VSV and vacuum modulator should produce no vacuum at 2500rpm with the coolant temperature below 131 F. They should produce low vacuum above 140 F. This is with TE1 and E1 shorted. If vacuum is being applied to the EGR valve somehow, the engine will run rough or die. A large amount of exhaust gas will cause your engine to misfire a bit. Check your vacuum line connections.

12-02-2006, 06:28 PM	#3 (permalink)
Weasy2k 3.4L 10K RPM In the works Join Date: Mar 2005 Location: Vancouver, BC Posts: 8,886 Thanks: 34 Thanked 76 Times in 65 Posts iTrader Rating: (6/100% )	HA perfect thats the info i needed. (I dislike these things) This also explains why the engine runs better when giving it gas...

12-02-2006, 07:16 PM	#4 (permalink)
Weasy2k 3.4L 10K RPM In the works Join Date: Mar 2005 Location: Vancouver, BC Posts: 8,886 Thanks: 34 Thanked 76 Times in 65 Posts iTrader Rating: (6/100% )	Still no go...i changed the EGR and replaced teh gasket again (have spares) to make sure its fine.... @Q$#) i pressurized the manifold itself without the egr and TB and it built up pressure with no noticable air leak....