I have been looking around the forum for a whileand could not find someone with the same problem so I finally decided to ask. I just bought a 1990 4runner. I do not know the maintenance history of it so I decided to do basic tune up stuff. I replaced the air filter, plugs, wires, cap and rotor and when I started it up again for the first time after doing all of these things it started right up and when the engine started to warm up the idle got pretty rough, dropped to 500 or less rpm and was almost quiting. I checked the timing when it was warm(with the jumper on the diagnostic port) and it was at 10 deg btdc. I tried to increase the idle speed to 750 and nothing happened. I could hear what sounded like an air leak so i took an unlit propane torch around all the vacuum lines and the only time the idle changed was when I was right at the EGR Vacuum modulator. Is it supposed to be sucking in air at idle or could this be the cause of my rough idle? When I say rough idle, I mean it sounds like it has a big cam in it causing a very lopey idle.

Thanks in advance for any help you could give me.

Corey

 

Should not be sucking air in. u can test them with a hand vacuum pump to make sure they are working properly, pull off the hose apply some vacuum, Idle should drop off and almost shut the truck off. if there isn't that much of a difference I'd say it's bad but then again it shouldn't be sucking in air.

 

alright well I think i may as well replace it then. I do not have a vacuum pump, but if it sucking in enough air I can hear it clearly over the engine noise I am sure something must be wrong. Is this a part I can only source from Toyota or is it something I could get from NAPA etc.

Thanks again for your help.

Corey

 

Corey, I got mine off ebay, sounds like its definately bad, mine did the exact same thing when a hole got burned in it from the lower hose falling off. I think its a dealer only part, but like I said, found a brand new one on ebay. If you cant find one i'll look for the card of the guy I bought it from, just let me know.

 

thanks, I will take a look but if you still have the info from where you got your it might make my search a bit easier.

 

For those who care I have orderd a new EGR Vacuum Modulator, it should be in tomorrow. I will let you know if that fixed the problem. I really hope it does.

 

I put on new vacuum modulator and replaced the vacuum lines that go to it and It still sounds like it has a vaccum leak at that point. I also know there is a filter inside of it so can it not be assumed that there is supposed to be air passing through it? My idle is still horrible.

Also, I am not sure if this would be having any effect on my idle problem, but i was stupid when I changed my plugs. I removed the intake tubing to get to the rear plugs and when i went to start the engine the first time the intake tubing was not connected, it was just laying beside the TB.
Would this affect anythign else that me be giving me my idle problem?

 

i am haveing the same problem sounds llike there is excessive air being pulled through the air filter kind of a gargalling noise? it has me stumped to been trying to figure it out for months now!

 

has nobody else had this problem? or is it even a problem?

 

I still have an odd idle, even after replacing mine, its better but not perfect, I haven't had time to work on the truck lately but if I find anything i'll be sure to update this post...

 

gargalling noise? that's the kind of sound and un-baffeled PAIR valve makes.