Hello I have a 99 5.9l ram truck . Having idle issues I'll start from when the problem started till now.

Tried starting my truck about a two weeks ago and it started and idled at 200 for about two seconds then died. Did this for thirty mins. Finally started and ran perfect for thirty mins in city traffic. Normal idle. So I suspected the iac. So I disconnected the battery replaced the iac didn't touch pintle installed it and plugged back on the battery. After that I start it and it idle at 1100 and it they a cel p0505 so I figured eh needs to learn so I drove it for a week and nothing and once in a while did the hard start idle. So replaced the iac again same steps and after two days did same thing cel still on same high idle. So I cleaned all the connectors and replaced the map the tps is only five months old. Cleaned the throttle.body all grounds and the PCm. Same thing...... I'm at a loss here at why the cel and idle are still high.??? Also no vacuum leaks I tested all hoses. Never idles rough never did no miss fires . Thanks for the help.

 

Check the wiring from IAC to PCM. Make sure nothing is rubbed thru/broken/otherwise not in good condition.

If that's all ok, might be a failing PCM.... I think the folks that have the truly expensive scan tool can actually test the IAC, and circuits... so, if you don't find anything, might have to pay the dealer an hour labor to diagnose.

 

I thought it might have been the PC also I failed to mention if I.move the pintle inward so it idles high it does move it. Back to the 1100 idle. I really want to avoid a dealer lol

 

Check the wiring, and reset the PCM again. Make sure the PCM forgets everything. Leave it disconnected for a few minutes, with the headlights on. (with the battery disconnected, no, they won't come on... but, it gives a nice ground path for any residual energy stored in the system.)

 

Okay I'll try that I'll get back to you in ten mins or so

 

Same thing no change....

 

replace TPS. throttle position sensor, drivers side of throttle body. about $35-45 at any parts store. keep all "good" old sensors as spares, they come in handy in cases like this.

 

I'll replace that as well if I unplug it while its running it changes the idle to erratic. Would the intake manifold air sensor cause this as it tells the PCm the air tempature and changes air fuel mixture.

 

i doubt it. my idle problems have always been either IAC (fail to idle), or TPS (fast or surging idle, or sometimes fail to idle)

 

OK. Either didn't touch pintle------or did------I am confused here. Did you remove the TB and clean the IAC port out real good? If not, try that....



Unplugging a sensor while running (and PCM is attempting to communicate with said sensor) cannot be helpful. PCM can lose its mind...

How did you test for vacuum leaks? Check the small plastic tubing that goes into the firewall very closely. These get brittle and are not obvious when they break back there in the dark and out of sight.