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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 ...


6

Your data logs tell me the following: Fuel trims are fine Here are some plots I generated from your data for both short-term and long-term fuel trims. The plot above (Bank 1 STFT vs Bank 2 STFT) show that there is no bank imbalance and most of the data points hover around zero STFT correction, which tells me that feedback from the O2 sensors is ...


6

The fact that you can smell fuel in the exhaust is a strong indication that the engine is running rich. This means that there is more fuel than required by the engine. There are many things which could cause this and the sensible course of action would involve hooking the engine computer to a scan tool to retrieve data about fuel trims, and O2 sensor health....


6

If I had to guess this sounds like a four cylinder engine, with one or even two cylinder's misfiring. Best guess is a problem with either a spark plug wires, or an ignition module. I'm looking at high resolution photos of your engine compartment and its not clear on what type of ignition system you have. Generally there are two types of systems. One has a ...


5

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 ...


5

Not familiar with your vehicle/engine specifically, but familiar with carbed engines in general. I would think the #1 thing to look at would be the choke. Pumping before starting a carb vehicle is normal. It gives it a squirt of fuel and sets the choke. The low RPM indicates that the high idle is not set, which likely means the choke is not set also. ...


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 you'...


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 ...


4

The stalling issues point toward problems with an engine control system (air, fuel, or spark), but again short of replacing the fuel pump, you have already replaced the parts most likely to cause those issues. The idea that the car will act normally on short trips is also strange. The problem that stands out to me is that the car has trouble accelerating, ...


4

First of all, the 5.3l engine (could be all of the Vortec LS engines, don't know) is thirsty. It drinks a bit of oil. Be aware you could be looking at up to 2 quarts between oil changes. I don't know exactly what the issue is, but it does have a bit of an oil control issue whether it has to do with leakage or burning. My '06 is this way. It has never ran bad ...


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 ...


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 time....


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

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.


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

When you say that it shakes when you stop at a red light, based on the context, I'm assuming that you mean when the car is fully stopped and the engine is idling. (If I'm mistaken about that and you mean that it shakes as it comes to a stop, I'd suspect a warped brake rotor.) I'm going to guess that the engine is running poorly at idle after the engine is ...


3

The data doesn't support it You measured your coil resistances to be within spec You measured your wire resistances to be within spec You've already replaced the plugs with ones that require less voltage to operate So while the bad-coil theory may explain what's going on, I'm not confident it will. Possible explanations for the readings obtained Off ...


3

Sounds like a possible evaporative system issue involving the purge valves that vent fuel vapor from the gas tank. If the OBDII -on board diagnostic code that triggers the check engine light is P0440 then that is the issue. If the purge valve remains open for too long it will eventually damage the catalytic converters by sending too much unburnt fuel ...


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

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 ...


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

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

Sounds like either a dirty throttle body, bad idle speed motor, or bad coolant temperature sensor. I would start with cleaning the throttle body. If there is gunk in there, the AIS may not be able to let enough air by to raise the idle. The AIS automatically set the idle speed based on several factors, mainly engine temperature. The cold idle should be ...


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 ...


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 ...



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