Once in a great while, you get very lucky with these cars.
For many years, I've struggled with having an idle BLM that was higher than all of the others. Many others on this board have the same problem. I've always chalked that up to my 57-lb injectors and high percentage of PCV flow at idle. In addition, as of last year, my cruise control would do a very weird thing - when I hit the "set" button, the car would start accelerating, and keep accelerating, until I hit the brakes (this is very scary if you've never experienced it!).
I finally took a shot at diagnosing the cruise control, and I figured I'd check the vauum lines running to the servo. So, I pulled the vacuum line off the metal line (the junction from metal to rubber that is between the FPR and driver side valve cover). I attached my Mity-Vac and squeezed away. Nothing, no vacuum at all. I was worried, because there are a lot of vacuum lines connected through that location (EGR solenoid, A/C controls, vacuum ball, and cruise control). That's a lot of vacuum line to check. So, I started by pulling the vacuum line off the EGR solenoid, put my thumb over it, and squeezed away on the Mity-Vac - BINGO - had 15" of vacuum very quickly. Hmmm, is the EGR solenoid supposed to leak vacuum like that? And, why would it be leaking? This is a 40,000 mile car.
There is a vacuum check valve between the metal vacuum line and the EGR solenoid. It's only supposed to allow vacuum to pass, and it's not supposed to allow boost pressure to go past it. Sure enough, this check valve had failed, which meant that 25 psi of boost was getting to the EGR solenoid. I'm pretty sure it's not designed to handle that, which probably explains why it's leaking vacuum like crazy.
So, I purchased a new vacuum check valve at Auto Zone - of course the hose barb sizes are different, so I had to buy some vacuum hose and connectors to adapt it to the factory lines. I installed that and capped-off the vacuum line that normally runs to the EGR solenoid.
I'm happy to report that this little change fixed three problems: 1) My cruise control now works normally, 2) My idle BLM dropped way down, it was 127 after a ten-minute test drive in stop-and-go conditions, and 3) my idle vacuum picked up about an inch or so (on my boost/vacuum gage). Wow, and it cost me less than ten bucks! Victory is mine!
I've ordered a new EGR solenoid - when it arrives, I will report back on whether installing it reverses all of these fixes. My thought is that the new EGR solenoid will not leak vacuum like the old one, so installing it will cause no changes. Most of us don't run EGR, anyway, so there's no reason why you can't just remove the vacuum line and cap it for good. I run a version of a Translator chip (like many othere), and those chips never command the EGR solenoid to operate the EGR valve - so, the solenoid is just there for show.
Just wanted to share my joy and hope that this helps somebody else fighting these same demons...
For many years, I've struggled with having an idle BLM that was higher than all of the others. Many others on this board have the same problem. I've always chalked that up to my 57-lb injectors and high percentage of PCV flow at idle. In addition, as of last year, my cruise control would do a very weird thing - when I hit the "set" button, the car would start accelerating, and keep accelerating, until I hit the brakes (this is very scary if you've never experienced it!).
I finally took a shot at diagnosing the cruise control, and I figured I'd check the vauum lines running to the servo. So, I pulled the vacuum line off the metal line (the junction from metal to rubber that is between the FPR and driver side valve cover). I attached my Mity-Vac and squeezed away. Nothing, no vacuum at all. I was worried, because there are a lot of vacuum lines connected through that location (EGR solenoid, A/C controls, vacuum ball, and cruise control). That's a lot of vacuum line to check. So, I started by pulling the vacuum line off the EGR solenoid, put my thumb over it, and squeezed away on the Mity-Vac - BINGO - had 15" of vacuum very quickly. Hmmm, is the EGR solenoid supposed to leak vacuum like that? And, why would it be leaking? This is a 40,000 mile car.
There is a vacuum check valve between the metal vacuum line and the EGR solenoid. It's only supposed to allow vacuum to pass, and it's not supposed to allow boost pressure to go past it. Sure enough, this check valve had failed, which meant that 25 psi of boost was getting to the EGR solenoid. I'm pretty sure it's not designed to handle that, which probably explains why it's leaking vacuum like crazy.
So, I purchased a new vacuum check valve at Auto Zone - of course the hose barb sizes are different, so I had to buy some vacuum hose and connectors to adapt it to the factory lines. I installed that and capped-off the vacuum line that normally runs to the EGR solenoid.
I'm happy to report that this little change fixed three problems: 1) My cruise control now works normally, 2) My idle BLM dropped way down, it was 127 after a ten-minute test drive in stop-and-go conditions, and 3) my idle vacuum picked up about an inch or so (on my boost/vacuum gage). Wow, and it cost me less than ten bucks! Victory is mine!
I've ordered a new EGR solenoid - when it arrives, I will report back on whether installing it reverses all of these fixes. My thought is that the new EGR solenoid will not leak vacuum like the old one, so installing it will cause no changes. Most of us don't run EGR, anyway, so there's no reason why you can't just remove the vacuum line and cap it for good. I run a version of a Translator chip (like many othere), and those chips never command the EGR solenoid to operate the EGR valve - so, the solenoid is just there for show.
Just wanted to share my joy and hope that this helps somebody else fighting these same demons...
