Could this EGR Problem be the source of my idle issues??

[Kdubslugga]

Im gonna feel like an idiot but i had no idea that the EGR Valve was Vacuum Acuated. The port on my valve is underneath the actual valve so i cant even see it. I was looking at a buddies EGR Valve and his vacuum port is right up top, so i said to him, is there supposed to be a vacuum line to the EGR Valve, of cousre he says yes and know im hoping that this is the problem!!!! I just got a new one becuase i dropped my old one on the concrete cracking the mounting bracket. So think this could solve my poor idle problems at start up?? No vac at the EGR Valve, could that cause idle problems???

 

[jrichker]

The EGR causes idle problems when it sticks open or leaks. It is supposed to be closed at idle.

Here's the theory & a test procedure...

The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping. It can also reduce HC emissions by reducing fuel consumption.

The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic vacuum regulator. The EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum. The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.

EGR test procedure courtesy of cjones

to check the EGR valve:
bring the engine to normal temp.
connect a vacuum pump to the EGR Valve
apply 5in vacuum to the valve.
if engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.
if engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.
if engine stumbled, connect vacuum gauge to the hose coming off of the EGR Valve
snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
did the vacuum gauge show about 5in vacuum?

if not, check for manifold vacuum at the EGR vacuum valve.
if you have manifold vacuum then connect vacuum gauge to the EGR valve side of the vacuum valve and snap throttle to 2500 RPM.
should read about 5in vacuum

 

[HISSIN50]

also, since you are adding missing stuff, really pay attention to Jrichker's post where it talks about the vacuum source to the EGR valve itself, be sure to not run a manifold vacuum line to that (the vac to the valve is switched upstream).

good luck.

 

[Kdubslugga]

jrichker is a walking Mustang Manual "lol" thats awesome man thanks a lot.

Can someone please post a pic of where the Vac line goes to from the Egr valve!! Thanks!!

 

[HISSIN50]

jrichker is a walking Mustang Manual "lol" thats awesome man thanks a lot.

well said, though i think he is better than that (his posts are comprehensive and understandable, unlike some manuals where you are flipping from chapter to chapter with bits and peices of incomplete thoughts and diagnostics).

We are fortunate to have him post on this site and share his vast knowledge.

and sorry, I dont have a pic. ill take a quick look to see if S&2B's has something on his site (that i can find). EDIT, the best i can find at first blush is a vacuum schematic by Tom (NOTE it is based on an 88):

http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

someone will post a pic for ya.

good luck.

 

[HISSIN50]

one more:

http://www.veryuseful.com/mustang/tech/engine/images/88Stang5.0Vacuum.gif

 

[Kdubslugga]

Apprictiate it man, both you guys have great knowledge of Fox Bodies, thanks for the diagrams!!

 

[TheUser]

The EGR is one of the things that confuses me. Here's my question: I have GT-40P heads and a cobra upper. The cobra upper doesn't use the EGR spacer, but has a place dedicated for the EGR valve. My question actually is how do the exhaust gases get back up to the valve? I read in the Probst book that they go from the exhaust manifold to the intake through the EGR valve, I've never seen anything hooked up to the headers to divert the exhaust back to the EGR?

 

[jrichker]

The stock plan for 87-93 is as follows:
The heads have passgages cast in them that brings the exhaust gases up to the lower manifold flange. The lower manifold has passages cast in it to pipe the exhaust gases to the upper manifold. The upper manifold pipes them to the EGR spacer between the throttle body & upper manifold. The EGR spacer mounts the EGR valve that allows the exhaust gases to enter the intake air flow under computer control.

This system works the same with the eariler Explorer manifold, which is very similar to the GT40 (lower is the same, upper is different).

Some models of the Explorer supposedly used an external piping for the EGR supply. I have not seen one, so I cannot say how it works.

 

[Kdubslugga]

Can someone please show me where the vac line connects to from the egr valve, ive narrowed it down thanks to the diagram but there 2 or 3 possible places i could put it and i just want to make sure i put it in the right spot.

 

[ninty1gt]

When I Put On My Typhoon Intake, I Put Those Egr Blocker Gasket Things, Am I Suposed To Block Off The Egr At The Spacer, Or Is What I Did Bad For Anything??

 

[jrichker]

Can someone please show me where the vac line connects to from the egr valve, ive narrowed it down thanks to the diagram but there 2 or 3 possible places i could put it and i just want to make sure i put it in the right spot.

If you are looking to connect the EVR (widget on the rear of the passender side strut tower) to vacuum, use any line that connects directly to the intake manifold.

 

[Kdubslugga]

sweet thanks man!!