Need some insight here. When I first got my GTA back on the road after a 10 year rest, I had a idle surge problem. No SES light so couldn't pull codes and everything looked normal. One day I was on the passenger side of the engine and just so happen to pull the second line coming out of the EGR solenoid and the idle is now dead on. No surge and no SES light. Been running like this for 2 months now.

This second like runs under and into the throttle body and splits before that, and goes into the charcoal canister. My question is, why would it cause surging idle?

Is this line important to the throttle body? I've since pulled the charcoal canister out but really want to hook that all back up.

 

Your vacuum system doesn't seem like it's connected right. The line from the canister should connect to the side of the throttle body (TB) (below the port for the CCV) and the EGR solenoid should connect to the bottom of the TB.

What's connected to the port below the CCV port on TB (Mine is on the passenger side)

 

What's CCV? And this is in regards to a 87 GTA. My sig has my old 89 GTA.

 

87-89 are the same. CCV is Crank Case Vent and allows fresh air into the crankcase when it's under a vacuum. It's on the opposite valve cover as the PCV. Hose goes from there to the TB. The PCV only allows air to go from crankcase to the intake manifold. Your CCV connection should be on passenger side valve cover.

 

Ohhhh gotcha. Haha.

Well I edited some pics and maybe they will give you an idea of how my vac lines were.

First one is the line coming off the TB. Second one showing the line coming from the solenoid, going under the TB and also to the canister.

 

Found this diagram. As you can see, the hose that goes up under the TB looks to be a single hose. On mine, it's a single hose, but has a T in it and then runs to the canister. So according by this diagram, and you, someone mucked up the routing huh.

 

To be more precise. Mine was routed exactly like this!

 

I figured it out!!

In the 85-86 one, the canister is different from the 87-89, but that's what I had on my car and it was routed like a 86. I need to get the 87-89 canister, and route it as such.

 

That 87-89 canister has the same hoses and routing as my 91. Part number at the dealer is 17092109 but I'd have the dealer verify it. May want to check a couple salvage yards and see what they have because they are not cheap.

You may want to visit the dealer anyhow to verify you didn't have an early 87 that used some leftover '86 parts.

 

Well hold on a minute. This is weird. I had a buddy send me a pic of his 87 GTA and his canister is the same exact thing in mine?? To me it all looks factory. This doesn't make any sense.

 

My Chilton's maual had the same diagram you got from Chevy86's post. They have been wrong before. I take it the vacuum diagram sticker that was on the hood is long gone?

When you pulled the line off the EGR solenoid, did you plug the line? You may have a vacuum leak in one of those lines to the canister or the TB. Vacuum leaks will definitely cause your idle to surge.

 

Well, the sticker is infact still on the hood.

And it shows the diagram of 85-86. So I guess that's the one I follow. What a let down!

 

Look for a vacuum leak.

 

To clarify, by hooking that up, if there were a vacuum leak, one would have to be in the line going from the solenoid yeah? So between that, the TB, and canister?

 

I need to think about this for a minute.

To recap, you pull the line at the EGR solenoid and it idles smooth. No plugs anywhere. Just pull it and it idles?

Have you tried to leave the EGR solenoid to TB line connected and plug the T that goes to the canister? That should half split it to give you a better idea.

 

You got it. Just pull that had line and it's smooth as butter. No cap or anything, just open.

I have not tried that yet but was thinking about it. Would eliminate the canister which I took out if there was something weird there. Gonna give that a go tomorrow and see what happens.

 

Also check your EGR solenoid and EGR. If it is constantly open, you are getting Exhaust Gas Recirc at idle and that can cause a rough or surging idle.

 

If there was a problem with the EGR, wouldn't it throw a code? Just curious.

 

Only throws a code if it doesn't open when it's supposed to. There is no check to make sure it closes. When the ECM commands the EGR active, it looks for indications that it actually went active. Here is a great write-up on EGR operation: https://www.thirdgen.org/egrdiagnose.

 

Well got it all hooked up but as soon as I hooked up the vac line going into the inline purge valve, things got wacky again. However, just connected to the TB, it was fine. So could there be a fault in that purge valve?

 

Any idea where to git an EGR valve solenoid? i know their discontinued.

 

I have a similar problem with my 87 GTA I found this Corvette parts site that has both solenoid and temp sensor available. Not positive its going to work, I think these are the only ones available.
Zip-Corvette.com
My car doesn't have the temp sensor now, and my Valve doesn't have a hole for it. Is it needed for it to work right?

 

Could someone please tell me where does the hose from the EGR valve connect to the solenoid... There are two connections .. Up or bottom?

 

can anyone here get me a part # for the egr solenoid, work at AZ an can't seem to find it

 

Nla, use one from a s10 a Cadillac or used f body or y body. Use the search to find post on the s10 and Cadillac conversion with part numbers for pigtail and solenoid.

 

I found two EGR solenoids in autozone, one has only one vacume line and the other has two like mine, but they are not rubber like in the pic, although the rubber could be added to lengthen the solenoid

 

I'm actually interested in reading up on this conversion however the search feature for the site is terrible and brings this post up as the only one related to search results with s10 and cadillac. Have you a link to any old threads by chance ?

 

https://www.thirdgen.org/forums/tpi/...-solenoid.html

lt1 style connector conversion

 

https://www.thirdgen.org/forums/tpi/...-solenoid.html

i could be mistaken on the s10 application but caddy for sure