Engine knocking and Idle problems

mavreix

Member
:
Protege, 02 ES
Okay guys some help needed here.

My protege DX decided it wanted to start idling real low/ knocking at the same time. I mean its fine when I first start up the car or reset the ECU for the first few minutes until its warm and then the idle just drops down to 200 rpm's or so and might shoot back up a little then go down. Whenever the rpms get low or I shift gearsin 1st or second it knocks a bit and the car itself has been acting really sluggish and when I'm not on the gas or in coasting the RPM needle drops real quick. It slowly got to be like this, at first it would stay at 500 rpms and then shoot up and it just got worse. Ive done a huge amount of research and it seems it might be related to O2 sensor malfunction, MAF/MAP sensor malfunction. But before I throw out hundreds for parts I was wondering if anybody had any ideas? Theres a dealership not far from where I live so I could get them to check it out but Ive never done that sort of thing before and I don't know if they will charge me to look or not. There is no engine light or codes of any kind yet. I don't think its a mechanical problem but rather an electrical problem but I haven't changed the timing belt yet and I'm at 140,000 miles, could that be the problem?
 
140,000 miles....you're likely due for a timing belt. Have you gone to Murray's / Autozone / Advanced Auto Parts, etc...they can usually run the "codes" for you for free in just a few minutes.

If you see a P0300, 301, 302, 303 or 304 code then you have had a mis-fire event in at least that 1 cylinder.

It sounds like you may have but, have you already checked these...
air filter / restricted air flow / MAP / MAF sensors?
fuel injectors?
throttle body / idle air control valve / cable linkage?
 
Theres no light so I dont think there is any codes. But Ill do that anyway tommorrow, its not the oil unless our cars cant use 10w-40. I dont know how to check a PCV for working order but I might change it anyway. My car is a DX 2002 2.0L I think its a sensor malfunction but I dont know which one. I've heard that I could test the Oxygen sensors by just unplugging them and the car would run in "default" mode but I dont know and Im afraid to try. Anyone ever done this method?
 
So I'm gonna test the whole unplugging sensors to find problem method unless someone suggests otherwise. I'll let you know how this goes by Monday, if unsuccessful Ill hit up the dealership as a last call. No engine light yet but I really haven't been driving it because I'm scared of major damage. Where is the IAC on a 2002 protege? I really doubt thats the problem but it might be a good idea if I checked it out anyway.
 
Okay so I pulled the Oxygen sensor and after 5 secs something clicked and the computer went into "limp" mode, which is default rich gas mixtures. The car runs beautifully now with no bad idle, or knocking. This really is a great way to test anything on the engine yourself and see if the problem is mecahnical or electrical. Im going to replace both oxygen sensors and then return the computer to normal mode. Thanks for everybodies input.
 
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