Problem, fast idle 0505 code? HELP

[hemibeep]

Car has fast idle, 1500-2000 rpm. INstalled a new Idle air control motor, NOTHING. tried to clear code(check engine) nothing....
Is there another cause of 0505 code?
I have checked grounds. I have chased vaccuum lines. No throttle stick.

Clues?
Hints?
thanks

 

[Steve-Indy]

Have you checked your intake manifold gaskets?

Common problem on 97's...hiigh idle was frequently the first symptom.

 

[hemibeep]

The gaskets were replaced during the motor rebuild about 2 years ago. I'll try the starter fluid check for vacuum leaks.

If it is the intake gaskets, that is not too bad of a repair, only about 30 bolts!

 

[Jack B]

The gaskets were replaced during the motor rebuild about 2 years ago. I'll try the starter fluid check for vacuum leaks.

If it is the intake gaskets, that is not too bad of a repair, only about 30 bolts!

The IAC will only control the idle to a certain point. If the the vacuum leak is too large the idle is going to go up, closed loop has to add fuel for the additional air. WD40 works as good as any fuel for finding the leak and easier to apply. How about the brake vacuum booster of the heater control vacuum line.

 

[hemibeep]

after replacing the battery, the idle is more normal. but, the 0505 code is still there. getting ready to try to check for continuity from the pcm to the iac plug for each of the 4 wires. Does anyone know operating values for each of the 4 wire leads. it appears two are 12+ volts in run. other 2 seem near zero volts. thanks

 

[Jack B]

after replacing the battery, the idle is more normal. but, the 0505 code is still there. getting ready to try to check for continuity from the pcm to the iac plug for each of the 4 wires. Does anyone know operating values for each of the 4 wire leads. it appears two are 12+ volts in run. other 2 seem near zero volts. thanks

The way to check the IAC is to watch the stepper action with a scan tool. There are actually four stepper solenoids integral to the IAC, if any one is bad you will have a problem. I would watch the stepper position with a scan tool and remove the heater vacuum line (rear passenger side of engine) and watch what happens. Also watch the position/direction during deacecleration.

 

[RAYSIR]

Pull out the IAC block off the air bypass holes and if it still idles you definetly have a vacuum leak. A blown or stuck open PCV can cause a fast idle too. If not obvious I use an IAC driver tool to check it's operation then from there the connects to PCM but rarely find wiring the problem.

 

[GTS Dean]

While it sounds very much like a vacuum leak to me too, Vipers are very sensitive to electrical gremlins. Many driveability problems seem to boil down to poor grounding, or weak batteries. I had troubles with weak and erratic idle. I tried cleaning the IAC motor, and checking fuel pressure. I was about to break down and put a new IAC in when I experienced starting problems. It ended up being the battery with a weak cell.

I once had high idle - slow return - and it definitely was the intake gaskets.

 

[hemibeep]

thanks for so many replies.
1. put in a brand new battery.
2. used starting fluid spraying around all intake ports. around brake booster. evap under headlight. etc. No change in speed.
3. added a ground from IAC to right stud on framerail behind headlight.
4. cleaned all front ground locations, with silicone contact grease.
5. installed a NEW iac and no change.
6. using the roe code reader, 0505 and it will not clear the code.
7. checked each of the 4 wires from PCM pin out to IAC motor plug for continuity.
8. car idle is lower, but I noticed the popping gone from decel from cruising speed.

I will try a few more of the suggestions above. Thanks for the input.
Dave

 

[GTS Dean]

Take to the dealer and have them reflash the JTEC from the MDS.