EGR cause to run Rich?

doctorj357 · Aug 27, 2018

Question - Will a direct vacuum line to the EGR solenoid cause the engine to run rich at idle? I have a 95 GTS with Edelbrock heads, intake, BBK TB, E303 cam. And have noticed the idling does surge a little bit, but just a little. Typically stays right at 1000rpms, but sometimes dips below. I have to imagine some of that is cam related. For perspective, I'm the 3rd owner on my car. All this work was done by the original owner and I'm trying to decode what was done, how, and why.

They still had the stock airbox in it. So I installed a BBK CAI. When I removed the stock setup i discovered there was a vacuum harness from the fenderwell, disconnected. Had Red/Green/Tan and White. I found that the Tan and White go to the air bypass solenoids coming off the smog pump. Well I deleted the smog pump and just plugged those lines. Just leaving the red and green lines. Here is the current setup

Now the car runs fairly ok, but I do notice the idling wonders a little bit, but most of all, just seems to run rich, even for a cammed car. I have the stock fuel system with 19lb injectors, and the car is tuned. After some checklist reading today, I realized the Red needs to go to the intake and the green needs to go to the EGR

But with its current configuration, with the EGR hooked directly to the intake, will that cause it to be Wide Open all the time? Can that cause any rich conditions or poor mileage? I've read a few suggestions here that it could cause a lean condition too. One additional thing I noticed. I installed a new PCV valve, (had a spare in box but I think original was fine) and also a Steeda oil catch can I had in a parts box. Its my first catch can, but was a little concerned I caught this much in my first 20miles. Is this normal? Or indicator the car is running too rich? Or maybe something else?

Chythar · Aug 27, 2018

You are correct, hooking the EGR directly to the intake will cause it to be open all the time. It's only supposed to be open at part throttle. The red hose feeds vacuum to the emission solenoids in the passenger fenderwell. The computer then decides when to put vacuum to the green hose, which opens the EGR valve.

Are you looking to restore the emissions equipment? It's possible that the red & green hoses (which are plastic and get brittle over time) are cracked and need to be replaced. Some folks simply unplug the EGR and disable it in their tune.

doctorj357 · Aug 27, 2018

Ok, well that probably explains that. But what would be the symptoms of being stuck open at idle?

Far as I can tell the hoses are intact, no cracks, no damage. What happened was the original owner did all these mods in the late 90s. Then in 2015, developed a detonation issue. Changed the timing, added premium, no-go. So overly concerned he starts taking the engine apart (intake/heads) to inspect for damage. cant' find anything wrong. Car then sits for 3yrs (work/life/honey-do list....etc) gets in the way.

One day, wife is complaining about making garage space and he temporarily puts car outside while cleaning up garage. Along comes someone, sees the car and offers to buy car as-is, engine apart & all. Pays someone to put it back together, and turns around and tries flipping it it for profit to some sucker.

Along comes sucker 'me' and buys the car. Of course I find out about all this after the fact, and made me concerned a little how the car was put back together. I have to imagine when they put it back together, they hooked those black vacuum lines up. One is correct, but the other shouldn't be there. I'm imagining here, but didn't know what to do with that vacuum harness and tucked it outta site.

So I did take the EGR out, did the test, its holding under vacuum just fine. I have no real reason to delete it other than for aesthetics. But since its there, might as well make sure its properly hooked up. But one thing I've noticed on this car, idling seems to be mostly good, but do detect a surge about 30-60sec after it warms up. The other issue is, for my mods, 3:27 gears as well, I'm getting something stupid like 10mpg. And I'm really driving it conservatively. So I'm left wondering if having that EGR stuck open from not being properly hooked up is possibly contributing to that.

I'd like to make it right before I delete anything. That way I can benchmark anything solved, or anything new that crops up as result.

doctorj357 · Aug 28, 2018

So somethign weird happened

I decided to hook up the red/green lines where they should go. Here are the things I noticed in order

Car startups with with HIGH rpm, near 2000 and then slowly falls down to about 1100-1200
Driveability is greatly improved. Doesn't take much to get the car going. But that high rpm is annoying
Decided to disconnect those lines, and cap off the solenoid on the EGR and the port on the intake
RPM drops down to 1000rpm upon restart, driveability is a little rougher, eventually in 5mi the CEL came on, so I shut it off, reconnected the red/green lines, restart, CEL is gone
Drive it for about 15mi and notice two things

A. Coming to a stop, the RPMS have a tendency to surge from the 1100-1200 and shoot up to 1600 and back down a few times.

Here is a video showing how after coming to a stop, the idle surges on its own. At the 39sec mark I poke the throttle a little bit
View: https://youtu.be/p_7Pl5SbxUY

B. When at a full stop, and quirks settle down, idling at 1100-1200 if I just feather the gas, it drops down to 1000 and has a little trouble recovering

Here is a video shows how the idle stumbles if I just lightly poke the gas
View: https://youtu.be/2kz-HjvkRCg

So at this point, I'm clueless what to do. I can leave it at is, aside from the surging idle the car drives great. Or I can disconnect the lines, car returns to normal'ish, and the CEL comes on. Or put it back to the way it was and have the EGR open all the time, rpms stay at 1000, no surges, drivability decreases a touch 'feels like a cammed car'.

I'm going to continue through the checklist still. I checked my TPS earlier, parked with the ignition on, but not running I was only getting .02v to the tps. But I haven't checked it while running.

doctorj357 · Aug 30, 2018

SOLVED - Turns out the Red goes to the EGR Solenoid, not the Green. I basically hooked these up in reverse, and now the car runs perfect. No more surging idle, no more CEL, no more rough take offs in 1st. I can actually see the EGR working now when under throttle. The way I had it hooked up before wasn't moving at all.

Also in disclosure I did take out my IAC and cleaned it up. Figured with old way the EGR being connected directly to the intake, meaning it was open 100% of the time, that IAC had to be founded pretty good. And it was......lol. Cleaned it up good and now the car is running like it should have been all along.

EGR cause to run Rich?

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