Hey Everyone,
I have a 2003 Chevy Cavalier that I have owned since new. It has 340,000 miles and I want to get to at least half-a-million. My wife was driving it last week and it started with a very rough idle and ran rough for 5-10 minutes until it quit running for her in the bank line. I came to get her and the car and started it by giving it some gas, but the idle was rough and jagged. Feels like it missing and gasping for air. Running on the road home at 30mph it seems almost normal, until i slow to a stop. Went to have the codes read at Advance and Auto Zone only coming up with PO440 woe the EVAP system, which has been showing for 200K miles. Have a clean K&N filter but no other modifications. I’ve done a lot of work myself and also have a good mechanic, but I don’t want to drop if off blindly. I’m thinking maybe the Fuel Pressure Regulator or the IAC Valve. Haven’t looked at the throttle body yet. Where should I go from here?
"Have a clean K&N filter but no other modifications"
Could you clarify this statement please? If it’s an oiled filter, these are known to contaminate mass airflow sensors and cause operating problems on some cars.
The P0440 code simply indicates an EVAP system malfunction. If that malfunction inhibits the ability of the gas tank to breath in, it can cause a vacuum to build in the airspace of the tank as he gas is pumped out, making it difficult for the fuel pump to maintain pressure and manifesting itself in exactly the way you describe… followed by a total fuel pump failure. I’ve even seen photos of the problem creating enough vacuum to collapse the fuel tank. If you’ve been driving for that long with an undiagnosed EVAP code, I’d bet lunch your pump has petered out.
Diagnosis can be deceptive, because the fuel pressure may test as good when the car is static and the problem rear its head when the pump needs to provide sufficient fuel pressure to keep the car going on the highway and has to fight excessive vacuum in the fuel tank to do so.
+1 to the above suggestion that the oil from your K&N filter may have contaminated the mass airflow (MAF) sensor. Clean the MAF only with MAF cleaner from your local auto parts store. And if that solves the problem, remove the K&N filter and put a stock filter box from a junkyard back on (with a new stock filter, of course).
Thank you for the help. I will check & clean the throttle body in the morning.
From the above note from ‘the same mountain bike’ ,The clean K&N has been oiled every 6-months for the last 8 years. It is clean since October cleaning/oiling. The original fuel pump went out about 5 years/150K miles ago. Since it was replaced I have to keep the engine running to consistently pump gas. If the engine is off I can only pump VERY slowly and the pump will cutoff multiple times. With the car running I can usually pump freely. I usually fill-up 3-4 times/week. I’ve never tested the fuel pressure, but I could borrow a gauge to start there if that will help convict or eliminate the fuel pump. Please excuse my ignorance, but where is MAF sensor? It does seem to run near normal at 30-45mph, I haven’t taken it any faster since this happened. It seems to stall with lack of fuel (when I accelerate it runs smoothly above 1500rpm) but also seems to run fine when traveling at 25mph in neutral with airflow. Let me know if this helps clarify
To my mind, you have confirmed that you have a serious gas tank venting problem and in addition to causing failure of your original fuel pump it is now causing failure of your second fuel pump.
Do you “top off” your tank when filling up? If so, you may have saturated your charcoal bed in your charcoal filter, effectively plugging the lines and preventing the tank from venting while you’re filling up AND preventing the tank from breathing in as the fuel pump pumps the gas out while you’re driving. Your gas tank breaths through the charcoal bed to prevent any hydrocarbon molecules from getting into the air. The charcoal acts as a “hydrocarbon filter”, if you will.
The MAF (Mass AirFlow) sensor is located on the intake snorkel just after the air filter. It’s a heated element that measures the amount of airflow by monitoring how much current is required to keep it hot. Oil from oiled filters can coat the sensor, baking onto the surface, and mess with the measurement. Not all cars have one, but yours does. Even if it turns out not to be the problem, and I truly suspect the EVAP system malfunction is the real problem, I still recommend going back to a dry filter. By using an oiled filter and by not addressing your EVAP code you’re causing long term problems.
A large vacuum leak or a ruptured fuel pressure regulator diaphragm could also cause a problem like this.
I can think of a number of things to check but have no idea how deep you want to get into diagnostics or how stocked the tool box is.
You must be doing something right to eke 340k miles out of it and still going. Most cars by this point have long since been recycled into tuna fish cans and buried at the dump.
OP, what is your engine? I admit that I might be wrong about the MAF sensor.
Anyway, when adding together all the symptoms including the long-term EVAP code, the earlier failed fuel pump, and the difficulty filling the tank, I’m still leaning heavily toward an inability of the tank to breath being the cause of the symptoms.
The IAC is number one on my list since the problem occurs mainly at idle. But as @the same mountain bike says, you also need to look into the EVAP system. I think you have two problems.
If you’re going to clean the throttle body use throttle body cleaner not carb cleaner.
Some throttle bodies/intake manifolds have a special coating inside that prevents deposits from forming inside them. Carb cleaner is harsh enough to remove these special coatings. Where throttle body cleaners won’t.
Thanks again. There is no MAF or MAP sensor on the 2.2L ecotech. I used to top-off until i realized there was such a thing as the EVAP system at 150K miles. I have not since.
Today I cleaned the throttle body with throttle body cleaner. It was dirty but not filthy. I also tested the fuel pressure coming in and it is a steady 58psi, maintaining at 56psi 2min after shutting the car off. This is leaning away from the fuel pump being the direct issue. The engine stays running, roughly, jumping from 500-700rpm. With the air intake housing on or off the rough idle is the same. It runs very level and even at 2K-3K rpm, until I turn on the heating or cooling system and then cuts off. I’m thinking more towards the Idle air control valve. Unless there is some other advice I plan to start tomorrow by replacing this. Thanks for the helpful advice.
Insigtful. Thanks I cleaned the IAC Valve and housing–They were caked in soot. I replaced after cleaning and the engine routinely she-off where it was previously varying 400-700rpms. I replaced and it improved greatly, but there is still an idle problem jumping from 400-600rpm at parked idle and with a small backfire occurring. nearly audible, but every few seconds. Any further suggestions. There is a MAP sensor, just not attached to the throttle body. Could this be the cause of the idle troubles. Would either the Oxygen sensor or bad injectors give this problem, and not throw a code? I’m almost at the end of my exploring and ready to take it in. Thanks for any future help.
