Idle speed problem
I removed and tried to clean it but it looks like is seal. Althougt I sprayed a cleaner and maybe reach the interior but I noticed when is running, if I remove the TPS the RPM increases that's why I think is working. If I removed the conector for the IAC, nothin happen. There's 12V on the IAC A terminal.
Do you think I have to go the parts store and try a new one? I spent a lot of money on all this parts in that store so they won't mind if I buy a new one, test it anf if is necessary, return the part back.
All of this start a week ago when I decided to do a routine maintenance and change spark plugs, air filter and IAC. Before this, everything was fine. I never check with an scan tool but I don't have Check Engine light and maybe was on for a long time and I didn't notice but the performance always was good...I think.
Last edited by ibaezpardo; Nov 5, 2010 at 05:14 AM.
Ok, here we go:
-8 new spark plugs Champion Double platinum
-New IAC
-New air filter
-Removed and cleaned TB
-New thermostat ( Old one was opened all time)
-New both O2 sensors
-Checked wiring for O2 and looks clean and intact
-8 new spark plugs Champion Double platinum
-New IAC
-New air filter
-Removed and cleaned TB
-New thermostat ( Old one was opened all time)
-New both O2 sensors
-Checked wiring for O2 and looks clean and intact
Now, to correctly determine if the IAC has failed, you need a scanner with bi-directional capability; You need to be able to control the IAC and compare desired vs. actual RPM. Without that ability, you're guessing. Unplugging the unit won't tell you anything. They're stepper motors, and will stay exactly where they were.
Now, does you idle drop significantly when you put it in gear or when the A/C compressor engages? If it does, then yes, it sound like and IAC issue (that includes connector and wiring). If not, you need to start looking for vacuum leaks. 1,000 is very high for a warm engine. There's a vacuum port on the side of the manifold that is capped from factory on most engines, but that cap deteriorates (or gets eaten my rodents), and causes a leak. And there are other places that it could be leaking vacuum as well. The easiest way to find a vacuum leak is with a can of carb clean or brake clean sprayed around the intake and vacuum hoses while the eninge is idling. If it has a leak, pulling in the cleaner will cause an over rich condition and drop engine RPM.
However, before you do that, you mentioned a whistle at part throttle. Sounds like your air horn gasket is shot. Replace that before you go looking for vacuum leaks, as it'll give you a false symptom and send you on a wild goose chase.
For one, get rid of those. These engines are designed to run best with cheap Champion copper plugs.
Now, to correctly determine if the IAC has failed, you need a scanner with bi-directional capability; You need to be able to control the IAC and compare desired vs. actual RPM. Without that ability, you're guessing. Unplugging the unit won't tell you anything. They're stepper motors, and will stay exactly where they were.
Now, does you idle drop significantly when you put it in gear or when the A/C compressor engages? If it does, then yes, it sound like and IAC issue (that includes connector and wiring). If not, you need to start looking for vacuum leaks. 1,000 is very high for a warm engine. There's a vacuum port on the side of the manifold that is capped from factory on most engines, but that cap deteriorates (or gets eaten my rodents), and causes a leak. And there are other places that it could be leaking vacuum as well. The easiest way to find a vacuum leak is with a can of carb clean or brake clean sprayed around the intake and vacuum hoses while the eninge is idling. If it has a leak, pulling in the cleaner will cause an over rich condition and drop engine RPM.
However, before you do that, you mentioned a whistle at part throttle. Sounds like your air horn gasket is shot. Replace that before you go looking for vacuum leaks, as it'll give you a false symptom and send you on a wild goose chase.
Now, to correctly determine if the IAC has failed, you need a scanner with bi-directional capability; You need to be able to control the IAC and compare desired vs. actual RPM. Without that ability, you're guessing. Unplugging the unit won't tell you anything. They're stepper motors, and will stay exactly where they were.
Now, does you idle drop significantly when you put it in gear or when the A/C compressor engages? If it does, then yes, it sound like and IAC issue (that includes connector and wiring). If not, you need to start looking for vacuum leaks. 1,000 is very high for a warm engine. There's a vacuum port on the side of the manifold that is capped from factory on most engines, but that cap deteriorates (or gets eaten my rodents), and causes a leak. And there are other places that it could be leaking vacuum as well. The easiest way to find a vacuum leak is with a can of carb clean or brake clean sprayed around the intake and vacuum hoses while the eninge is idling. If it has a leak, pulling in the cleaner will cause an over rich condition and drop engine RPM.
However, before you do that, you mentioned a whistle at part throttle. Sounds like your air horn gasket is shot. Replace that before you go looking for vacuum leaks, as it'll give you a false symptom and send you on a wild goose chase.
The RPM never drops. Are Ok when cold. After reach 195 degrees, are over 1000-1500
Sorry the dumb question...what's the "air horn"
The air horn is the top of a throttle body or carburetor, where the air cleaner or intake tube attaches. On your truck, there is a gasket. If that gasket is damaged or missing, you get that whistle, as it is pulling air in front of the air cleaner through a small opening.
Yesterday I was checking some vacum hoses and tighting the junctions with tie wraps. I tested again today and noticed some change in its behavior:
-After reach 195 degrees, loose the idle, remains at 1000 RPM or 1500 RPM.
-Heater inside cabinet start to work. Never worked since I bought the truck. Is there any relation between the heater and the vacum?
- I hear a whistle when I'm driving and decrease the aceleration.
-Checked the fuel economy: 10 MPG combine city and highway with A/C working
What's the next step to recover the idle spped? What I did wrong?
-After reach 195 degrees, loose the idle, remains at 1000 RPM or 1500 RPM.
-Heater inside cabinet start to work. Never worked since I bought the truck. Is there any relation between the heater and the vacum?
- I hear a whistle when I'm driving and decrease the aceleration.
-Checked the fuel economy: 10 MPG combine city and highway with A/C working
What's the next step to recover the idle spped? What I did wrong?
Yesterday I checked the TPS and looks OK. Voltage increases at center wire with the throtle advance.
I checked the MAP sensor and voltage should increase with RPM but is not. I bought a new one today and will install tomorrow morning. I will test and post results
I checked the MAP sensor and voltage should increase with RPM but is not. I bought a new one today and will install tomorrow morning. I will test and post results



