1998 Protege Codes 0170 & 0421
 

Hey, guys. Tackling the 0170 code first, I think I have a vacuum leak, with the EGR valve solenoid (aka EGR vacuum switch purge) being part of the problem. Does anyone know how to cheaply test the solenoid, and the solenoid booster too? Trying not to buy to many new diagnostic tools.

I Believe I'm talking about the right part. The EGR solenoid is attached to a bracket on the left side of the exhaust manifold (when you're looking at the engine). It has two hoses. One hose connects to the back of the manifold, and the other connects to the solenoid booster, which is located on the left side of the fuel injector rail. Any suggestions would be appreciated. Thanks.

-Jim

The second code is catalytic converter related. Do the following:
Use Lacquer Thinner (not paint thinner). It will also help clean things. Yes it works fine, i've done it, so has Tanprotege.


http://www.rona.ca/images/0263016_L.jpg

Difference Between Paint Thinner & Lacquer Thinner | eHow

Jim: I think you are bit confused about the terminology. Mazda uses a "EGR Boost Sensor" as if the EGR would boost something. It really is a MAP sensor: Manifold absolute pressure. It sits on the firewall, passenger side. Follow the vacuum tube down to the back of the intake manifold and pull it off. Then use a strong piece of wire, about 3" long and poke into the nipple. If you feel resistance push through. This spot clogs up and keeps the "EGR boost sensor" from sensing the vacuum. Therefore it will not allow the EGR to open.

noggin told you what I would do about the 421.

Codes 0170 & 0421
 

Okay, I'll definitely take your advice on the boost sensor, but the part I'm talking about is attached to a bracket, on the left side of the manifold. But this part does look a lot like the boost sensor. It's also called the "vacuum control solenoid". It's Mazda dealer part no. FS0518741/5KT49090 (see first picture in link below). This part also has a vacuum hose connected to the manifold. I once noticed that the end of the hose connecting to the "solenoid" was disconnected. While the other end was connected to the manifold I could feel a semi-strong vacuum as I touched the open end. When I connect the other end to the "solenoid", my RPMs go down a few thousand, with idle becoming a bit weak. when I take the hose off the idle becomes normal.

Please let me know if you see the part I am talking about and if the idle dying down when I connect it means something is wrong with this solenoid. Thanks.

Part link: http://stores.ebay.com/IRENS-AUTOPAR...=p4634.c0.m322

Jim: I have not messed with this part, but maybe I should.
Still: this thing will operate on an electrical signal that is controlled by the computer. The computer needs the MAP as a parameter. Make sure the nipple I talked about is open. I would also replace the vacuum lines with new ones. Then try it again with everything connected.
I don't know what kind of voltage the solenoid receives. Maybe you can measure it. Then you could apply the voltage and see if the rod moves. Maybe Kevinkpk knows.

Okay. I decided to replace all vac hoses before going any further. does anyone know the sizes of these hoses (i.e., diameter, 7/64 inches). the dealer didn't know, which was surprising.

To my knowledge, ecm end devices are either 1-5 or 0-5 volts. Solenoids not directly controlled by computer are battery voltage, i.e 12 volts

"Okay. I decided to replace all vac hoses before going any further. does anyone know the sizes of these hoses (i.e., diameter, 7/64 inches). the dealer didn't know, which was surprising. "

That's not surprising at all.

Here is a suggestion: drive to the nearest auto parts store. After properly securing the vehicle ,open the hood an pull a sample of vacuum hose. Enter the store with said hose in hand and carefully approach the counter. When the clerk says: "Hi, may I help you?" you answer in a calm voice: "I need 15 ft of this." while you give him the hose.
Watch what happens next!