Massive? not really. The check valves kind of keep it under control, if one or more is not bad also. Anyway, here is a pic of the diagnostic vac test port from my 98.

 

Both are working fine now..

 

Mine doesn't has that cap. Check in the picture..

 

That pic you posted is too damn small, I can't see shat! LOL Could be on the other side, but my 2000 does not have one either. Why? I don't know, I think it's ridiculous and sucks though.

 

Ok, let's star from the beginning, the whole history to see if you guys can help me:

I owned this truck for four years now. Replaced starter motor, new radiator, air filter,oil changed as scheduled, A/C compressor replaced,new calipers, rear bands, new tires, installed a radiator for tranny, new belt and tension belt, new battery, two new rear axles and bearings, new rear seal for tranny, as I can remember. Everything has been working properly in my truck except for the heater (never works) and an stucked thermostat (open).
Two months ago I noticed something wrong in my tranny while I was towing my boat (6000 pounds). I continued used the truck after that but problems with transmission start. Some day, I noticed the RPM at about 1500 RPM but I thought it was the same problem with the tranny, maybe it was stucked in 2nd gear or 3rd gear or something like that. This RPM increases was only one time that day. I decided to repair the tranny and sent the car to the shop. The tranny is OK now. I spent some money on this truck, that's why I decided to keep this truck for a couple of years more and I made some maintenance on it. I replaced the spark plugs. I checked with an scan tool and gave me P0505 (Idle malfunction). The O2 sensors are not giving to me any code but when you check all the monitors, they shows "inc". As per scan tool manual, that means "incomplete or not good". I replaced first the IAC. I drove the car and the problem began. When you drive for a while, when you stop, RPM goes to 1000~1500. As time pass (aprox 10 minutes), they return to 600 RPM.I cleaned the throtle body. No solution.
I decided to replaced both O2 sensors. I did it and got the same problem when I conected the scan tool ("inc") is showing for both sensors. Why I'm receiving the same problem if I installed new parts??
I replaced the thermostat. Heater start to work.
I replaced MAP sensor. No solution. I installed gasket on the air cleaner intake (never was there). Same problem. I have been looking for a vacuum leak but I cannot detect any.
Now, I noticed today a water leak at passenger side (inside below the carpet). Do you think guys this truck deserves to repair the water leak or is better idea to put the whole car below the water in a canal??????

 

Thamks for describing this so well. I have a 99 v-10 that has had the exact problem yours is having. I have been considering a lake to drive it into. On friday after just dealing with it for some time it finally just wont stay running unless you have your foot on the accelerator pedal keeping it running.

As my problem progressed it started idling high after getting to operating temp after some sustained driving. I would just wait it out and it would go back to normal. having changed my o2 sensors earlier i ruled them out. It then progressed to my cruise control not working. Since I dont do much long freeway driving I didnt much care. Then after a little while longer it stopped idling high and then began iding low, about 400-500 but would stay running. Again I didnt much care because I am a carpenter and it was still getting me to work and back. Now i have to care. It wont stay running without driving two footed.
Yes I am one of those people you probably woudnt want to buy a car from. I do change the oil and some regular maintenence but other than that if it ain't broke, dont fix it until you know what it is.

I still dont know what it is for sure so thank you for detailing your problem so well. I didnt mean to bust into your post with my problem, I just thought you might want to know what could happen next if you dont figure it out right away. Ha Ha.

Thanks to all who have been responding as well

 

Maybe the IAC is a defect.



If your CC is not working, you have a vacuum leak most likely.

 

[QUOTE=zman17;2308675]Maybe the IAC is a defect.

New IAC installed. Voltage on it. Removed and checked if it goes out and in and looks OK. Looks like is capable to regulate the RPM when I start the A/C or when I shift

 

Thank you.

Since I have to address this tomorrow. I will post my findings tomorrow as soon as i can or figure out what mine is. I realize we have different motors but I swear the exact same problem. Desperation of not being able to work helps the speed to get it solved.

Again thank you ibaezpardo for detailing your prolem so well. And thanks again to all who have responded.

 

I meant the new IAC is a defect possibly. And how did you check that it goes in and out?