2004 S60 Throttle Problem and P0507

[csh]

I have a 2004 2.5T AWD (153k mi.) and after I serviced my PCV system I took the car out for a test drive and when I returned home and was parking in my driveway I noticed that there was no response from the throttle just off idle. If you move the pedal slowly there is no change and then it will hit a spot and rev up over 2k RPM. As a part of the PCV service I removed and cleaned the throttle body. After a number of drives, the check engine light has come on. I went to the local Autozone to get the codes and the only thing that turned up was P0507 'Idle Air Control System RPM Higher Than Expected'.

So here is how things are behaving at the moment. When cold start the car and it idles high as normal and then decreases the idle speed. While still cold the throttle seems to work as expected. Once warm the idle drops down as expected, but then there is the dead spot just off idle when pressing on the accelerator. It also does not return back to normal idle and most of the time it will settle in at 900RPM with no extra load like AC when in Park or Neutral. P0507 means the idle is too high and could be the result of a vacuum leak. I honestly don't think that it is a vacuum leak. With the exception of the high idle and the throttle dead spot everything seems to be normal. Idle is smooth and steady and with the exception of the throttle dead spot engine seems to run normally while driving. There are no surges other than when I move the accelerator past the dead spot. I did check for vacuum leaks by spraying throttle body cleaner near various spots with no results.

I suspect that I my ETM may have gone bad. I wonder if my handling and cleaning of the throttle body may have pushed it over the edge. If I go through the time and effort of removing the throttle body, I am thinking that I should just go ahead and install a new one for both the peace of mind and I value my time.

Just for reference, a few months ago I replaced all of the evap hoses under the hood to fix an evap related code, so all that is solid now. That leaves only the intake manifold to the head and the banjo bolt as the potential vacuum leaks that could bypass the TB.

I am open to suggestions before I pull the trigger and

[csh]

Based upon other reports of ETM problems, I pulled the electrical connector from the ETM and cleaned the plug and receptacle. That did not fix the problem. After watching how it will go from a normal idle and then slowly creep up to 900RPM the I wonder if the ECU is moving the throttle body to either match an airflow to the TPS reading or to get the TPS into a reasonable range. I think it may be time to replace the ETM.

[jonesg]

I can't recall where I read it but someone wrote the techs at volvo often replace the plug if the etm is disturbed on higher mileages, once its disturbed they have trouble reconnecting it, they cut it off and pigtail in a new plug.

[csh]

Problem Solved!

I did two things and one of them likely solved the problem. I was checking things out under the hood and noticed that the vacuum line that comes off the side of the intake manifold near the air filter box were somewhat loose. I could rotate the line by hand and shift it around on the fitting. I slid things around until it was tight on all fittings. I then got in the car and turned the key to the II position and waited for over a minute before starting the car. I started the car and when it warmed up the idle dropped down to where it used to ~650RPM. I checked the throttle and no dead spot/sudden jump in engine speed. I did go back to the vacuum lines to see if I could move them around to introduce a leak to see if the problem would return and I could not get it to act up again. So I went and grabbed the oetiker clamp tool and snugged up a couple of the clamps, but not all since two of them did not appear to work with the oetiker tool. I'll have to replace those clamps later.

Does leaving the key in the II position for 60sec actually recalibrate the TB? Given that the DTC indicated a possible vacuum leak it certainly could have been that but I was unable to confirm since I could not cause those hoses to leak enough to get the problem to return. I will note that these vacuum lines got stressed a bit since they were still attached to the manifold as I moved it out of the way to service the PCV system. I should also add that the electrical connector on the harness still seems to be in good condition. It was a bit oily, but it was not broken and the locking tabs were still intact.