QuestionQUESTION: I have spent several thousand dollars trying to repair all the codes that have come up with my check engine light including the catylitic converter just this week $600...every time I repair one thing another thing comes up for repair...I'm at the end of my rope with how much this is costing me....is there something wrong with the check engine light? What is wrong with my car? Now it says I have to repair the fuel trim...what is that? PLEASE HELP
ANSWER: The Protege is a fairly reliable and simple car.
You may be the victim of a shop improperly diagnosing the faults and making you pay for it.
Most MIL (malfunction indicator light) issues are emissions related devices. There are only a few devices that become common problems. I'm not there and since can't read the fault codes that come up so I'm operating in the dark with your issues.
If you give me some history and the symptoms that were associated with them I might be able to piece together your problem and help with a solution of some kind.
Is is a manual or an automatic?
How many miles?
In order from first to last what has been done and what brought you to the shop, ie a light on or a drivability issue.
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QUESTION: It's a manual transmission, 102,000 miles...the code that came up after I replaced the catylitic converter was P0170...'Fuel Trim'...the problem is, that whenever I fix whatever code has popped up, another comes up afterward and I have to fix another problem...how do I know that what they're fixing is really in need of repair, or if the computer is broken or there is a wiring issue...this has been going on for a couple of years now.
ANSWER: Like I said the Protege is a simple car. It is unlikely that the computer is simply throwing codes for no reason. If a fault is detected within the system that the computer monitors and controls the MIL will come on.
The code P0170 is a fuel trim code. Commonly linked to a MAS (Mass Airflow Sensor) issue. The MAS may be dirty or have a poor connection or it could be failing. Many times a technician will move the sensor to check the air filter if so it could have been damaged or disconnected. Locate it, unplug and re-plug it. If you can open the line attached to it a spray cleaner (brake cleaner or throttle body cleaner) can be used to clean the wire element. Take care because it is a fragile device.
Disconnect the battery negative side and depress the brake for 10 seconds, then reconnect the battery and drive the car. This should reset your computer. If the MIL comes back on you definitely have a fault. Have the code read again to determine if it is the same or another one.
The OBD2 monitoring system is great but it's not perfect. Just because the computer gives a code does not mean that the part associated with the code is bad. Many people waste loads of money listening and relying on just what the computer says is wrong. Sadly so do many technicians as is likely the case with you. The codes are a guideline and the symptoms must be read and other test performed before a parts swap is done.
For example Fuel Trim. Fuel trim could be related to a misread of the exhaust gases or a vacuum leak or a bad air flow sensor. It is highly unlikely that the computer is failing though it can happen and does in moist climates or if the car has had water inside. Though a failing computer will result in drivability issues that would be obvious.
Speaking of drivability issues, what if any are you having? Stalls, sputters, won't start, poor economy or just the MIL?
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QUESTION: Yes, I've had some drivability issues come up recently, mostly the sputtering when I first start out in first gear, it's like it chokes and doesn't engage or something, very jerky start out, and sometimes it does stall, but mostly the jerking...I'm sorry if I sound cranky, but this has been a nightmare...and the problem is, that in Oregon if you have a check engine light on, you can't pass DEQ, so I HAVE to repair every single code that comes up...the catylitic converter code cost me $600...I do appreciate your help, and understand that you're not here...Thanks
AnswerI'm just going to give you a few scenarios. Start out simple.
Have you ever had the fuel filter changed? Fuel pressure or flow can cause these type issues and this is a maintenance item. Also air filter and inlet tubing, check them for restrictions.
Ignition break down: - Spark plugs, Ignition wires. Symptoms - Hesitation, Sputtering at low speed, usually smoothes out at speed though a misfire may still be detected at speed. Common issue normal maintenance.
MAS (mass air flow sensor) - Symptoms can vary, however low speed misfires, sputtering and killing along with puffs of black smoke at the tailpipe are common. A MAS unit can fail at times and work well otherwise. Many times the unit will duplicate the fault if the connectors to it are manipulated or if the unit is tapped while the engine is running. Check for an air bleed/leak somewhere between the throttle plates and the MAS unit. Listen for hissing associated with a vacuum leak while the engine is idling. A vacuum gauge will show a fault on the engine side of the throttle plates. 12-17 HgM is the normal reading at idle.
I think you are looking at one of the above problems. Though other issues (approx. 12 others) can cause the symptom and code P0170. Incorrect ignition timing, a faulty crank/cam position sensor, failing fuel pump, front oxygen sensor, temperature sensor, air inlet temperature sensor.
I wish I could give you a simple how to but, this isn't possible without hands on leg work. Though converters loose efficiency after 90k the only reason to change one is if it can't pass emissions due to it or it rusts through or becomes blocked in which case the car will not run. Sorry to bring bad news but, they may have gotten you on that one.
