Hey everyone, I've got a recurring check engine light and I haven't been able to identify the problem. The code almost always set when I am driving on the highway with the car fully warmed up. I can clear them and it will take a couple days, maybe a week to come back.

Codes:
P0440 Evap Emission Control System malfunction
P0507 Idle Control System RPM high
P0410 Secondary Air injection system malfunction

I have been looking for vacuum leaks, and haven't found any. I've replaced the IAC. The car runs like a top, but I get tired of seeing that stupid light constantly.

Edit:
Important info - this is my 01 SC2 (DOHC)
I have also changed the gas cap

 

P0440 is a general evap code that indicates the ECM has detected a leak in the evap system relating to the vapor pressure inside the system. Usually a bad gas cap seal, but not in your case.

Usually for the s cars they throw specific code for the purge valve or vent solenoid, but I suppose it can't tell where the leak is so you get this more general evap code.

These cars are known to develop leaks in the filler pipe to the gas tank. This would confuse the system since it would see everything else is functioning properly but the vapor pressure in the tank is low.

Since your idle control is high, you may have a purge valve stuck open. This would give a steady flow of fuel vapors into the intake manifold and might be pushing your idle speed up enough to **** off the ECM.

What does it idle at when warmed up? Auto/manual?

Spray around the intake manifold where each runner meets the head listen for an idle speed change. Be sure to spray the bottom as well as the top.

 

Well the code for the high idle is set, but the actual behavior is a little odd. When I am driving, if I slip it into neutral, or engage the clutch at a stop, it will maintain RPM around 1500-1800, but then when the car actually stops (reaches 0 mph) the idle speed will drop down to sub 900. Very occasionally it will not drop when the car stops. Now this behavior is always at the end of my commute. My commute is 5-10 minutes to reach the interstate, 39 miles at 65-75 on the interstate, and then 5-10 minutes to destination. Generally it does not do this at the start of the commute.

Normal cold idle is somewhere around 700. (Manual transmission)

Would a code reader show the tank pressure with live readings? I just upgraded my code reader and it can do a lot of live readings, and graph them.

Any way to test a purge valve?

 

I'm assuming you obtained a scanner not a code reader. A full featured scanner should be able to display both the vapor pressure in the fuel tank as well as the pressure at which the purge valve opens, meaning you can wash the pressure build in the system and then when the purge valve opens you'll see the value drop toward zero until it closes. This is when the gasoline fumes are getting routed back into the intake manifold. Or actually maybe to the throttle body because otherwise it would be unmetered fuel and that would screw up the fuel to air ratio.

What scanner did you get and what software are you running?

Cold idle on a manual dual overhead cam at 700? I'd like to see what your scanner says for RPM because I would expect the engine to be in the verge of stalling at 700 RPM. My DOHC manuals have always idled right at 850 which is supposed to be the requested/commanded idle RPM to reach.
At least for first and second generation s cars. They did change the engine design a bit for the third generation s cars so I actually don't know what the idle speed should be for 3rd generation.

Measure the resistance across the ECTS when the engine is ice cold and once it is warmed up and post the readings here. Usually when the ECTS goes bad, it tells the engine it is -40° after which the fuel mixture is richened and the car can be difficult to start and may idle high for quite a while since the ECM never sees the temperature increase of the coolant in the head.

The amount you paid for a decent scanner Will reach its return on investment in about 12 months when factoring the cost of labor when you take your vehicle to a mechanic. Plus you get to learn every nook and cranny of your vehicle, even the ones you don't want to.

Getting back to the car, people especially with third generation s cars seem to have the same issue you are describing. Sometimes the culprit is scuz in the throttle body and intake. Other times the throttle position sensor is worn and it does not correctly indicate the throttle position to the ECM. I wouldn't rush out and buy one. If the IAC was that disgusting, I can't help but think the rest of the throttle body and the output from it to the intake manifold is also pretty cruddy. Pay special attention to the edges of the throttle plate and the back of a throttle plate.

The secondary air system design on the third generation s cars is a freaking nightmare when it stops working properly. There are many posts across the internet that are far superior to anything I could piece together in a couple of sentences so I will leave that one for you to investigate. Look up a video by Richpin on YouTube. He has made probably 100 videos addressing different repairs to Saturn vehicles and is a great source for how to information.

 

I'll say up front, my RPM's are estimates. I haven't recorded them definitively

This is the scanner I picked up.


I'm going to hook it up during my commute to see what it's doing.

 

Nice.

Do not try to configure it while you are driving. You will crash.
Select your PIDs to monitor while you are sitting in the driveway before you leave. Give yourself 10 or 15 minutes time prior to leaving for doing this. You don't have to measure everything on one trip. Remember you can use the graphical representation or just create a dashboard type thing with the raw numbers changing on it. I would say for the purge pressure and vapor pressure in the tank to use the graphical mode.

Most of the parameters you want to measure live are not the basic OBD2 parameters. You will have a list to choose from, and for lack of a better term, you kind of need to dig through the entire list to see what's available in order to decide what to monitor. I believe it varies from vehicle to vehicle because not all vehicles share the same information.

Please do not crash. Start recording the live data before you pull out of your driveway. Don't use up all the memory on a 30 minute drive. The purge operation is a cyclical one, and so the vapor pressure in the tank should also cycle. I don't believe you'll need that much data to rule out or indict that part of the system.

We shall see.

 

Well that was all kinds of interesting.

I just got this scanner and I'm still learning it. As an initial foray today I reset the code, and put engine temp, rpm, speed, and EVAP purge valve DC on the graph. I recorded about 20 minutes of replay data. As a tech person hard numbers like this are fascinating.

Watching the replay, the solenoid popped to 100% 13 minutes. Temp is 158 and the speed is 64. No idea if those matter, but it's DATA.
The solenoid fluttered at 14 minutes, then stayed at 100% for the rest of the run.
The code didn't reset during this run, so I will spend more time looking through my options for the trip home, maybe buried in the list is a fuel system pressure reading.

 

My scan run has identified one issue. My ECTS appears to be reading 20 degrees lower than it should. My reported temp the whole trip was about 172 degrees. According what I'm finding, the thermostat should be 192.

 

Or your engine is running cold because the thermostat is stuck open or partially open. Where is the temperature gauge needle? Should be at least slightly above first tick. Usually halfway between first and second tick.

The Purge sticking at 100 sounds as though it is stuck open which would indeed lead to pretty much no vapor pressure in the tank because everything going through the evap system is just running right into the engine / intake manifold.

This may be a purge solenoid issue that controls the valve, a wiring issue where it is shorted, a loose or missing/disconnected hose, inlet or outlet, etc. If it is like first and second generation s cars, it is on the side of the engine nearest the windshield. It's a bit difficult to get it from above without taking anything off but you can. You can also get at it from underneath if you get the car up enough to get all of your arm into that space.

 

I'm going to do more testing, but the purge valve seems to be opening at about 3K RPM, when I slow down it closes. My run today was lost when I tried to save it, but I glanced at it on the off ramp and it it showed the valve dropping to 0%.

I still need to dig into what I can measure better. but the temp being off is my first thing to fix. I