Question about Cars & Trucks
There are many things that can cause a vehicle to run bad and it looks like you've tackled a large portion of them. I'll just add a few more items to check to help with solving it.
First thing I would do is, with the engine running, listen for any vacuum leaks. It will be an audible hiss that, if large enough to cause poor operation, will be easily heard over the sound of the engine. Using a piece of rubber hose with one end to your ear and the other end pointing at various components of the engine can really be helpful in pinpointing the exact location of the vacuum leak. If found, repairing this will improve engine performance, regardless of whether it solves your current issue or not.
Next, oxygen sensor(s) are a prime suspect. If you can, hooking up a scan tool, you can see if there are any codes. A scan tool that can graph the voltage of the upstream O2 sensor can let you know if the sensor is working or not. It should go up and down once or twice a second, with voltage readings between around 0.1-0.2 up to 0.8-0.9 . If it isn't varying around at all, then it will need replacement.
After that, testing the Idle Air Control Valve (IACV) is what you want to look at doing. It's simple to inspect, test, and replace. First, remove it check the pintle for excessive carbon build up. Clean it off with carb cleaner. Next, you need to perform an ohms test. With the connector unplugged, perform the following tests:
Measure resistance between terminals A and B.
Measure resistance between terminals C and D.
-These two readings should be between 20-80 ohms. If not, replace.
Measure resistance between B and C.
Measure resistance between A and D.
-If not infinite resistance, replace.
Here's a wire diagram for the IACV.
Next, remove the EGR valve to see if it's dirty. If so, clean it. If it is bad, it would most likely have an engine code associated with it, and a dirty EGR is a more likely culprit.
Next, test the Manifold Absolute Pressure (MAP) sensor. You'll need an volt meter for this one. With key ON engine OFF, back probe (as in, keep it connected to the sensor and probe the connect/wires) terminals A and C. You should get the 5 volt reference signal. If not, the wiring or the ECM is bad. Now probe between A and B. With engine off, it should read about .5 volts at sea level. Now turn the engine on. At idle it should read ~1.5 volts and it should read ~4.5 volts at wide open throttle. If not, inspect for vacuum leaks or replace the sensor.
That should pretty well cover the water front for possible solutions to your poor running engine. Hope that helps.
Posted on Dec 12, 2013
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Posted on Jan 02, 2017
It is probably the fuel pump. If I remember the number correctly, this fuel system needs about 50 lbs to open a valve.
Until this valve opens, no fuel gets to the fuel nozzels.
Posted on Apr 30, 2010
I am having the same issue on Mitsubishi Galant 02. Clattering on acceleration, herky jerky idle. Pulled a code multiple cylinder misfire. My mechanic's diagnosis is bad valve cover gasket causing oil to seap into the spark plugs and bad timing belt, which I have not replaced at 150k miles. I do however know my fuel injectors do need cleaning, he hasn't ruled that out either. Have you pulled any code on it? I have read on engine knock sensor going out on some of these also. Hope this helps some.
Posted on Oct 22, 2010
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