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sprinkles08, ASE Certified Technician
Category: Car
Satisfied Customers: 21436
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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My 2003 Mitsubishi Eclipse Spyder

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My 2003 Mitsubishi Eclipse Spyder GTS has been reccently throwing codes: P0171, P0174 which are new, and this one has been throwing about couple months before the other ones: P0660. I keep hearing clicking sound also at idle and everytime the car starts to click near the intake manifold in a black device where two fairly medium sided hoses attach to to the intake manifold where the air filter hose attaches to. The cars RPM would start to idle up and down. Up when it clicks and goes down after clicking, Idle is roughly around 700 to 800 RPM varying. I reccently changed all my sparks plugs and i was having a cylinder 2 missfire and really bad acceleration on highway speeds. I checked the resistance on the wires and they were fine and in ranged except on cylinder 2. I saw the conductive coating on the spark plug wire was burned and was turning to a black powder and so i changed all my Spark plug wires and fixed that problem. I also had a code P0430 before i changed my spark plugs and wires, but not anymore. So now my question is how do i fix the codes P0171, P0174 and P0660? I know what they all mean, but how do i fix them? The first two codes mean both bank 1 and bank 2 of my fuel system is too lean and the other is my intake manifold tuning valve circuit is open. What can i do to determine what is faulty and how can i fix this? PS: I had to unplug some vacuum tubes and accidently unplugged ones that didnt need to be unplugged while changing 1,3,5 spark plugs and might have placed them wrong. I might need a diagram for both sides of the engine for the vacuum hoses. Maybe i missplaced a hose and it is causing this? Thank you.

Hello and welcome to JustAnswer!

P0660 is for the control circuit of the variable induction control solenoid, which is essentially the same as a manifold tuning valve. This solenoid is on the front of the plenum near the right strut tower. This is an electrical code that sets when the engine controller doesn't see a correct voltage spike from the solenoid when it tests it. This can be the solenoid itself, lack of power to it from the MFI relay due to a wiring issue, or a wiring problem between the ECM and the solenoid. The first thing you'll want to do is unplug the solenoid and check it's resistance, which should be 29-35 ohms, replace it if out of this range.

If the solenoid is ok then check for power at the solenoid with the engine running.

If ok, the next step would be to test the wiring between the solenoid and the ECM.

The fuel system lean codes can be caused by a number of things. One of the most common causes is the mass airflow sensor, which measures the amount of air flowing into the engine. If it's signal is incorrect then the air/fuel ratio will not be correct. Cleaning the sensor may help, otherwise it's signal can be monitored on a scan tool.

It could be low fuel pressure. If fuel pressure is low then it will cause the engine to run lean and these codes to set.

If the fuel injectors were restricted with debris or rust that would cause it also, but that's not as likely to happen.

A vacuum leak can cause the codes. Make sure all vacuum lines are intact and attached and make sure there are no leaks at the intake, throttle body, or between the mass airflow sensor and engine.

An oxygen sensor can cause this on a single bank, but since you have the code setting for both banks it is less likely to be an oxygen sensor, since it would be two failing the same way at the same time.

An incorrect coolant temperature or intake air temperature signal can cause these codes.

An incorrect reading from the MAP sensor can also cause this. It reports vacuum to the ECM and the signal is used for calculating engine load, injection quantity and timing and ignition timing.
Customer: replied 3 years ago.

I will go and test the sensors in a little bit. i work from 11 to 4pm pst. I will get back with my findings. Thank you so much.

You're welcome!
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Customer: replied 3 years ago.

After driving my car about for 30 minutes, after taking off the intake manifold from replacing the spark plug wires and spark plugs my Check engine light went off and the codes were cleared by themselves. I believe the It needed time to readjust because the vacuum hoses i took off before. I really do appreciate for helping me. Oh, i also checked the wiring and checked the ohms and the volts the sensors were producing and they were all in range from the recommendation that my manual gives.

Customer: replied 3 years ago.

Ok...... The codes came back... I even went to and connected my reader and it reccomended to change my MAF Sensor. The readers says: P0171, P0174, P0660, P0421. The reader tells me what they are and what they mean, but i am unable to find the problem, i might have to replace an O2 sensor anyways for the P0421 code for Bank one on the number 1 cylinder side, but the other stuff is stumping me still. After all the testing too, but the Variable Induction Control selenoid i haven't tested yet, just the MAF selenoid and that tested good and i also used MAF sensor cleaner i got from the part store. Still throwing code.

The mass airflow sensor signal was correct when watching it on a scan tool?

Customer: replied 3 years ago.

No, i had to test the sensor with a voltmeter. My scantool only allows code reader. I tested Terminal #4 and measured 12.11Volts and book says 12Volts. #3 Terminal 5.05Volts and books says between 4.8 to 5.2Volts. I then checked Terminal #5 and measured with Ohms and book tells me it has to be below 2 Ohms and it measures 45 Ohms. It said if it didn't measure below 2 Ohms then to check terminal. This is all i was able to get. It told me to test with engine off, so i did. Another note, am i checking the right terminals? Because it is called Volume Airflow Sensor, not Mass Airflow Sensor and also looks like my Intake Air Temperature Sensor is also located on the Volume Airflow Sensor. The book tells me to check those terminals and i did. Do you think the 45 Ohms may be causing this problem for the codes since it said it has to be below 2 Ohms with engine off?

An actual functional test of the sensor requires monitoring it's signal on a scan tool while running, but since you found the sensor's resistance to be incorrect then yes, it's going to need to be replaced.
Customer: replied 3 years ago.

Okay, Thank you. I will be going to the part store and ordering a new VAF Sensor. I will report if this fixes the problem. Thank you.

You're welcome!
Customer: replied 3 years ago.

Okay, I ordered a new Volume Airflow Sensor, It's the same as the Mass Airflow Sensor and also has the Intake air temperature sensor, so i got two in one. however, i cleared the codes and after about 10 miles, they came back after installing the new sensors. I checked the resistance when i unplugged the harness from the Sensor and checked to make sure its not a faulty ECM/PCM and it was in range from what the book specified. I do however notice that while my car is at idle. It fluctuates up and down, it never did this until the codes. I keep hearing a clicking noise everytime it happens and sounds like the solenoid that connects to two hoses. One that goes to the intake and one that dissapears into the firewall. My guess its the purge solenoid. I am a novice at this and could be wrong though. The codes i do remember came as this clicking started and was pretty loud, but only if i open the hood i can hear it. I also see that everytime it clicks, the idle would fluctuate. While my car is warming up, it doesn't do any of this until after its fully warmed up, then the clicking noise comes and idle will fluctuateup and down. I connected my ipad with and elm adapter to my obdII and gave me minimal live data with dash command as an app. My RPM fluctuates up and down getting to almost 500 up to almost 800 RPM while the solenoid is clicking.

Let's try disconnecting the purge solenoid, clear the codes and see how it does. See if it runs normally and if the fuel system lean codes still set.

Customer: replied 3 years ago.
Okay, i cleared the codes and disconnected the Purge solenoid. No codes came on, but the idle was still fluctuating inconsistent with the recommended RPM for my car. After letting the car running for about 10 minutes, no codes. I reconnected the Solenoid and still no codes, but it started to click really loud again and every time the idle would fluctuate, the solenoid would click with it. I drove around all day today an no codes came on and then all the codes came back awhile ago. I had the purge solenoid connected while driving because i didn't know if it would be bad to drive without it. But i did disconnect it during idle in the driveway as i explained. So, it ran the same with the purge solenoid off, but do you want me to drive without it connected? What should i do next? I am in College for Automotive Technology so any terms you use, i am fairly familiar with, but still a novice with engine components as in diagnostics.
Customer: replied 3 years ago.
Oh... almost forgot. The codes didn't come on until i went at high speeds like 45 Mph or more, i just realized it didn't come on until i was going about 45 Mph to the college. All of them. Street speeds didn't set the codes and believe when i cleared it before, it did the same thing..
I doubt the purge solenoid is related to the fuel system lean codes but you can definitely drive the car with it unplugged and see if those two set or not.

Another thing we should do is take a look at temperatures. After the car has sat overnight and before it's started, go in and take a look at coolant temp and intake air temp and see if they match ambient temperature very closely.

Closely check for vacuum leaks anywhere from the intake ducting to the engine, any hoses off or damaged, and make sure the intake itself isn't leaking. You can spray some carb cleaner and suspected joints with the engine idling, if spraying an area changes the idle then you've found a leak.

If you have a mechanical vacuum gauge make sure the actual vacuum matches the MAP sensor's reading.

If all of this looks ok then I'd next recommend checking fuel pressure under a load while driving and see if it's low.
Customer: replied 3 years ago.
Okay, I will go and do this tomorrow morning. Thank you so much. I will get back to you on this.
You're welcome!

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