YotaJunky

My engine has been idling rough for the past month or so. It doesn't seem to matter if it's cold, warm or hot. I'll get sporadic stalling after hard stumbling, which may occur right after I start it up. Sometimes, it idles just fine, with perhaps mild roughness. My idle fluctuates within about 300 rpm, irregardless of how the idle screw is adjusted. Acceleration, fuel consumption and power all seem fine.

I've pulled the plenum, replaced the plenum gasket, reset my TPS, replaced the throttle body gasket and checked all vacuum hoses and air hoses for leaks. I've got no codes.

I've noticed that my EGR doesn't get as hot as it used to, even after about 30 minutes at highway speeds. I've checked the EGR and the pipes are clean and deposit free. I'm wondering if the idle problem has something to do with the EGR. Is there a way to check for proper function of the EGR valve?

Any suggestions would be greatly appreciated. I'm currently at a loss for how to proceed from here.

Troy

4Crawler

iTrader: (3)

One tip is to tap on the EGR valve body with a screwdriver or small hammer to see if the idle smooths up. If the valve is sticking open, the tapping will free it up so that is can close. If the valve is stuck open too bad, this won't work. The other way to check it is to remove it, and with the valve upside down, fill it with carb cleaner or similar and see if fluid leaks out (it should not). Then you can pull a vacuum on the valve and it should open and release the solvent. A pistol cleaning kit and solvent work well to clean out the insides of the valve.

DH6twinotter

If I remember correctly, you can check the EGR valve by sucking on the vacuume line going into the EGR valve. Your truck should idle rought or cut off if it is working properly. You can also try hooking a vacuume line from your plenum to your EGR and it should idle rough. I used the small hose that goes around to the brake booster.

I think that is the right way to do it from what I can remeber. I'll check it tomorrow afternoon jut to make sure.

Well, hope you get it figured out!
Have fun.
Daniel

4Crawler

iTrader: (3)

That is the way to check that the EGR valve is opening, but it won't help that much on checking if it is closing properly (sticking open). If the idle were smooth and you pulled the EGR open with vacuum and the idle got rough (as it should) then you release the vacuum and the idle remained rough, that would point to a sticking valve.

YotaJunky

That makes good sense. I'll give it a try. Can I use a separate line connected to the air chamber as a vacuum source? I noticed a couple of plugged up lines along the passenger's side of the plenum that I may be able to unplug and then connect with an extra hose. If not, I'll have to get myself a vacuum pump.

Troy

YotaJunky

Small hose that goes around to the brake booster? Do you have a pic as I don't want to mess it up if I pick the wrong one.

I hope I figure it out also... Thanks for the encouragement.

Troy

4Crawler

iTrader: (3)

A small hand operated vacuum pump with a gauge on it is very handy. You can use the pump for testing vacuum operated things and the gauge can check vacuum readings and you can even fit one out for bleeding brakes and clutches:



http://www.harborfreight.com/cpi/cta...emnumber=92474

MTL_4runner

If it was stuck open then you would just get no change in idle when vacuum was pulled on the EGR....
Not sure I understand why that would not work.

Maybe you guys were both saying the same thing in different words.

4Crawler

iTrader: (3)

I suppose that would work, of course assuming the EGR was the cause of the problem. It could also change the idle, for example if the EGR was not able to close fully due to clogging but it could still open farther. And in that case tapping on it may not be enough to close it. Bottom line is there is probably no 100% test with the valve in palce to see if it is working properly or not.

YotaJunky

I ran the EGR system through a battery of FSM tests and I'm confident that it's functioning as it should. That rules out the EGR valve, VSV for the EGR, the EGR modulator and vacuum hoses connected to the aforementioned. The rough idle continues to persist and I'll look elsewhere now.

Troy

4Crawler

iTrader: (3)

I've run the FSM tests as well and noted that they mostly check that the valve is opening properly. So you might still have a problem with the valve closing properly. Have you tried the tapping test? That was a trick shown to me by a Toyota dealer mechanic and it does seem to be a good diagnostic tool.

YotaJunky

Yes, I did tap it with the end of a screwdriver and did not notice a change in idle, which may not indicate that it's closing properly. I suppose the only way to ensure that it isn't the EGR valve is to get a new one.

Troy

4Crawler

iTrader: (3)

Either replace or test/clean it off the engine would be some options.

leiniesred

read both rough idle posts.

My 3vze idles with the screw in all the way at 250 RPM.

I noticed no mention of spark plugs. I had a camry that was so reliable, i forgot to change them for a VERY long time. idle got bad. Changed out REALLY worn plugs and it ran like new again.

check out those plug wires while you have 'em off. since you did all the FSM tests, I think you have the simple ohm meter to do it!

Also, cleaning intake and throttle body makes a 150 RPM difference in my truck. It seems like the goo on the back of the throttle butterfly and the venturi there has a lot to do with it. I spray in intake cleaner with the car running and my hand on the throttle to keep it running. bog it down with intake cleaner, let 'er clear out, repeat. note idle speed is higher again. adjust as required.

MTL_4runner

The only way to know if you should be replacing it is to remove it and do the test as 4Crawler mentioned.....otherwise you are just playing parts replacement:

"The other way to check it is to remove it, and with the valve upside down, fill it with carb cleaner (or similar like isoproply alcohol, etc) and see if fluid leaks out (it should not). Then you can pull a vacuum on the valve and it should open and release the solvent. A pistol cleaning kit and solvent (or just intake cleaner and a toothbrush) work well to clean out the insides of the valve."

YotaJunky

I've already done all of the aforementioned, and them some. New Denso plugs (properly gapped), new NGK wires (good continuity), new rotor and cap, new TB gasket, new plenum gasket, new fuel filter, new air filter, checked all vacuum lines and air hoses, cleaned TB twice, and reset the TPS. No change. No codes.

I appreciate your input, and please keep them coming. These threads help all of us.

Troy

YotaJunky

I'll do that this weekend. Thanks for the input. I'm leaning more towards a fuel supply or clogged injector(s) problem. I Just did a cylinder balance test by pulling out one plug at a time and checking for a drop in rpm. There didn't appear to be an issue there. I'm now looking at the temperature sensor beside the CSI timer switch.

Thanks again for all your input! Please keep them coming...


Troy