KCS7621

Hi everyone, new here and hoping for some assistance with my '94 4Runner. I've been reading through some related EGR threads but they're quite old, and don't really answer the question I have.

The car has had a strange problem in regards to idling for the past few months. When I start the vehicle, the idle is TERRIBLE. It feels like a big ol' hot rod rumbling away. It has absolutely no power if I try to drive it in this condition. The strange thing is though, if I let it warm up for a couple of minutes without touching anything, or if I just rev the hell out of it, get the needle up to 3000 then let off the gas, the idle smooths out the car runs fine for the rest of the drive, gas mileage is the same as always, power is the same as always. The severity of the rough idle is affected by how long the car has sat (much worse first thing in the morning, than in the afternoon after errands), ambient temperature/weather doesn't seem to bother it.

The car has its check engine light on, and is showing code 71 or "EGR system." (thank you paper clip code reader!)

I'm willing to replace the EGR valve if that will solve this issue, but it's a pricey part, and I'd like to know if the idle issues mentioned above sound like those of a failing or filthy EGR valve or perhaps something else.

The car is a '94 4Runner, 172k, V6 engine, 4WD, auto trans. Had a new motor put in about 30k ago.

I hope I've provided enough data to get some help. Thanks everyone

-Krystle

MudHippy

Could very well be clogged up and/or the valve is sticking open. You might try cleaning it with some carb cleaner spray(I prefer brake cleaner myself). You'll probably have to remove it first to get it positioned so you can spray some up into all the openings and down the tube that feeds into the throttle body.

KCS7621

Thanks Mud. Is it safe to run the engine without the EGR in place to see if it idles more smoothly? I think I read in other thread it's illegal but just for testing purposes, is it safe?

xxxtreme22r

perfectly safe, might throw a code on the efi trucks, but on my carb'd truck I had to disable mine to install a weber carb. other than it might run a little warmer than usual, nothing wrong with disabling it. All you have to do is remove the vac lines to it and plug the lines. Keep in mind though, if the EGR is stuck open disabling it is not gonna do anything and will still do the same thing.

MudHippy

Not only is it "safe", it's "safer". Your engine will thank you for it. And will respond by running better, especially if it's what's causing it to run rough. Make sure you get that hole in the intake sealed up good though, or the vacuum leak will cause it to not wanna run smooth either.

Won't get rid of that code. BUT...there's ways around that if you're interested in the EGR delete permanently.

KCS7621

Hmm this is interesting and sounds hopeful. Forgive my UN-knowledge, but is there way for me to see if the valve is getting stuck open while still attached? Is this a visual thing or is this something I need to check with a vacuum meter, yada yada.

Second thought, could these 'symptoms' be from a failing fuel injector, or cold start injector since it regulates itself after such a short time?

MudHippy

No, if it's stuck open. It's probably stuck...meaning ain't nothing gonna close it but cleaning the junk out so the valve can close.

I wouldn't think it could be the injectors, of either sort.

Only other thing that I'd suspect would be a vacuum leak of another sort(EGR stuck open is essentially a vac leak too). Which could be leaking in air from anywhere from the lower intake manifold to the AFM.

LifterCatcher

Mud please explain how to get rid of the code, I have zero emissions testing here is Missouri and would love to rip all emissions bull out of the truck.

So EGR is closed when Vac is applied and then opens when Vac goes away?

Thanks

MudHippy

1.10k ohm resistor to replace the EGR temp sensor. Radio Shack.

2.Other way. Closed when no vacuum applied. Open when vacuum applied. Vacuum applied to the hose at the top of the EGR valve. Which means if it's stuck open then it's already resisting being closed by the spring that pushes the diaphram out and closes the EGR valve. Applying vacuum pressure to the hose at the top overcomes the pressure applied by the spring which then pulls the diaphram in and opens the EGR valve.

https://www.yotatech.com/forums/f116...my-egr-108005/

Flash319

I would check your COR relay or change it. I have had them be flaky and the fuel pump stumbles at startup causing a low pressure situation.