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6

You need to check for leaks in the air intake A leaky air intake can explain hunting idle and I don't think spraying carb cleaner is always conclusive as some cracks can be really hard to see/detect. There are several ways to check this: block the air intake completely The easiest way to do this is disconnect the airbox and cover the piping before the ...


6

This wont do any damage to your engine until you have an accident making a mistake with the pedals:) The IAC would only doing the same function that you are doing manually. I do think you have more of a problem than the IAC being faulty, since it should just add extra air when you switch things on like the lights, air con etc. Maybe your throttle ...


4

The Problem can be with the engine not getting enough ventilation. Problem: In your car the ECU is programmed to raise the rpm when it detects a stall or the RPM dropping down so if there is problem with your air filter which is not allowing much air into the engine and causing a stall but not noticeable your ECU will fight it to keep it in working ...


4

Thanks for the great detail. Considering this is a bit of an odd issue, I'll try thinking outside the box a little. But first I would use a multimeter to test the coolant temp sensor, then o2 sensors. Perhaps even a quick check of the upper radiator hose to make sure the thermostat isn't stuck open. I say to check these first because it sounds like ...


4

I know this vehicle as a Yaris; 1NZ-FE engine, and that is the vehicle I am commenting on. Toyota does not mention a specific procedure for an idle relearn in their official service information. Even the procedure for throttle body replacement does not mention a relearn procedure. The info does not state that a procedure is not needed, it is silent on the ...


4

My suggestion is that your IAC valve is sticking. This would mean it is jutting in/out and not providing the amount of air for the computer to get the engine to settle. Since you've already cleaned it and the passageways, about your only other recourse is replacement.


4

As HandyHowie said, this won't cause any damage. However, there is a better way, based on the assumption that you have a foot on the brake because you leave the car in D at the lights. If the car will still idle in N with a bad IAC, select N as you're coming to a stop and put it back in D as you press the gas pedal to set off again. Make sure the revs are ...


3

Good example of PID graphing. Consider the possibility that these symptoms are caused by a mixture issue instead of timing. The STFT is adding fuel and the symptom of hesitation further suggests that the mixture is lean. It is likely that if O2(B1S1) and INJ PID's were included these would show a lean O2 with a corresponding lengthening of injector on ...


3

Or could be your mass airflow sensor because I have similar issues and that is what's wrong with my car


3

(EDIT NOTE: I made a bad assumption about the HEI distributor, so deleted all of that nonsense. Please do the following to see if it is an issue, though.) Please check the following: Take the distributor cap off so you can observe the rotor Put a socket on the crank shaft snout bolt (where the main crank pulley is at) Turn the crank clockwise until you ...


3

I think you have two completely separate issues here (brakes & starting). Since the engine is turning over, the starter is not bad. If there was a vacuum leak causing unmetered air to enter the engine, it would be running differently. It could just be that your MAF or other intake located sensors need cleaning for the starting. As for your brakes, it ...


3

So I finally figured out the problem. First off I had a defective O2 / Lambda sensor, which I replaced. However, this had little or no noticeable effect on the problem. The valve cover gasket was completely shot, with oil constantly coming out and also leaking into the spark plug holes. I fixed the gasket, which also didn't solve the problem. However, ...


3

You need to go back and look at the firing order of the spark plug wires you installed. If you get two out of place on a four cylinder engine, you now only have two good firing cylinders, and depending on which two got switched, one of them may even be firing the cylinder at opposition to the rest, not allowing the engine to get anywhere close to operating ...


3

Possible Answers We were hoping for a little feedback regarding this issue prior to attempting an answer. A few things come to mind regarding the problem description and we'll run through a few of them for you. Regarding Stalling Fuel Line - Your fuel filter may be impeded and require replacement. Since you have not indicated this happens at higher ...


3

The most common cause of this complex of symptoms is leaking intake manifold gaskets. Test for this by spraying a squirt of carburetor cleaner up and around the intake manifold. If the engine smooths out for a few seconds then there is a leak. The second most common cause is failure of the mass air flow sensor (MAF). I offer no quick tests for this part ...


2

1) Does that diagnosis sound correct? Seafoam sounds like a good way to go, but in this case it isn't going to cure the ill. The throttle body itself needs to be cleaned. I found this video which should show you pretty much how to clean it (as long as your engine is the same as the G35 in the video). Since the engine has reusable gaskets, as long as you ...


2

This may well be the smoking gun That "grommet" is actually a fuel injector seal. It is designed to keep air out and prevent fuel from escaping the intake manifold. If it is compromised then fuel can leak out, which will explain the presence of the dark stain. A quick way to confirm this would be to turn the key in the ignition to the 'On' position to ...


2

There appears to be a similar case on the Cobalt forum, where compression test figures are reported to be around 220 psi, roughly double what you're reporting. If this is the case for your vehicle, it would seem that the problem is related to a lack of compression and not fuel, air or spark.


2

Guessing. May be due to looping of 2 governors? Your car software tries to maintain the idle rpm. The AC temperature governor tries to maintain temperature, but some clogs in coolant path or issues with compressor leads to variable load on engine. Make sure AC system serviced once.


2

Apparently it was diagnosed by a specialist that there is a hardware / software problem with the ECU (Magneti Marelli) that is causing all this problems, and needs to be changed. There is nothing wrong with the sensors, coil pack or mechanical parts.


2

Based on the codes, I'd say race fever's spot on: P0300 - Random/Multiple Cylinder Misfire Detected P0116 - Engine Coolant Temperature (ECT) Circuit Range/Performance Problem P0304 - Cylinder #4 Misfire Detected P0174 - System Too Lean (Bank 2) Explanation I believe what's happening is the coolant temperature sensor is giving no ...


2

I believe you have a bad Engine Coolant Temperature Sensor (ECT in Ford nomenclature). The code P0116,the smell of gas, and the rough idle are all symptoms of a bad ECT. Its Ford's part number F5AF-12A648-AA. Get the OEM part. Its about $25. Be careful replacing it because your car has a plastic intake manifold that tends to break.


2

You probably need a new lambda sensor. Here's why: You're right - the lambda sensor needs to reach a certain operating temperature to function properly. Until it reaches that operating temperature, the engine ECU will assume open-loop operation and not rely on the sensor's signal to determine whether the engine is running rich or lean. Your tests and data ...


2

The symptoms are consistent with deposits in the throttle body. There are other potential causes. These deposits accrue in the intake manifold over time. They build faster with short trips and low quality fuels. Inspection and cleaning of the throttle body would be first thing to look at for this symptom. This engine is equipped with a computer controlled ...


2

The engine computer looses is idle speed learning whenever it drops below nine volts even for a short time. The problem here is the starting battery or its connections. Hook up a voltmeter across the battery terminals then crank the engine for 15 seconds. The voltage should remain above 9.6 volts. If the voltage drops below nine the computer will loose the ...


1

The air taken into the engine from the charcoal canister via the purge valve will be saturated with fuel vapors. The engine ECU will not be expecting this, so the engine will run rich. You would expect the fuel trim to be out.


1

I love the methodical approach taken to solve this issue. In the absence of concrete data from a scan tool it will be hard to definitively tell what the root cause is, but there are some prime suspects. The one thing made conspicuous by its absence is the condition of the throttle plate. It is possible that the throttle plate was partially stuck due to the ...


1

Given the tests already completed and the stated symptoms and the lack of trouble codes, the most likely failure is an inoperative or stuck closed idle air control valve (IACV). The fact that is runs with the throttle open a bit verifies the engine and fuel control system operates reasonable well.


1

I decided to check the engine bay while the car was running and immediately noticed a bright continuos spark on one of the battery terminals. Turned of car and went to fix it but the terminal was almost red hot and burnt my fingers. Eventually I managed to clean the terminal again and tighten some of the wiring eyelets (ammeter connection) that were ...


1

Sounds to me like the IAC valve (Idle Air Control Valve) needs to be replaced. It's not a hard thing to replace. The IAC opens and closes to allow air into the throttle body when the throttle blade(s) are closed (which is at idle). It might be dirty or have debris lodged in it which is causing it to act up. I've been able to replace them on older 2005 ...



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