1995 Chevy Cavalier

Tiny
HANDYA
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  • 1995 CHEVROLET CAVALIER
Engine Mechanical problem
1995 Chevy Cavalier 4 cyl Two Wheel Drive Automatic

The head was replaced on my 1995 Chevy Cavalier, however it is pushing out a lot of fuel and is idling very high. Need to know what to do to resolve the problem
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Tuesday, March 2nd, 2010 AT 7:35 PM

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Tiny
CARADIODOC
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What do you mean by "pushing out a lot of fuel"?

If you mean dripping from the exhaust pipe, that's probably water vapor. Nothing to worry about. If you mean the exhaust manifold is glowing orange, the ignition timing is retarded and the fuel is finishing burning after it leaves the cylinders. If you mean fuel mileage is bad, and you smell raw fuel at the tail pipe, suspect an exhaust leak before the first oxygen sensor. Between the pulses of exhaust flow, the momentum creates pulses of a slight vacuum. Outside air can enter the exhaust system through the leak and be detected by the oxygen sensor. The engine computer will see the extra unburned oxygen and add fuel by holding the injectors open longer in an attempt to achieve the proper mixture. Even though more fuel is entering the engine, the oxygen sensor continues to see that fresh air coming in through the leak. Oxygen sensors do not react to unburned fuel, just unburned oxygen. No matter how much extra fuel enters the engine, the O2 sensor will always report a lean condition.

A similar problem can occur from a vacuum leak by the intake manifold. The extra air might enter only one cylinder and again, be detected by the O2 sensor, but the computer can only add fuel to all injectors equally. Most cylinders will have too much fuel while the computer still sees the unburned oxygen. A misfiring spark plug can do this too. The unburned oxygen is detected by the O2 sensor; the unburned fuel is irrelevent. The computer increases fuel to all cylinders but there will still be that darned unburned air.

If none of these things seems to be the problem, you can use a hand-held computer, (scanner) to read the short and long term fuel trims. High positive numbers means the computer is trying to add fuel above the factory preprogrammed starting values. High negative numbers means the computer sees there is too much fuel entering the engine and is trying to do something about it.

So, ... The question remains. What do you mean by "pushing out a lot of fuel"?

Caradiodoc
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Wednesday, March 3rd, 2010 AT 12:27 AM
Tiny
HANDYA
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The information was not helpful, problem is that when you remove the spark plug from the head, gas pumps out of each spark plug hole as if it's a pump.
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Wednesday, March 17th, 2010 AT 7:14 PM
Tiny
CARADIODOC
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OH! It's good to have details.

I assume the spark plugs are also wet with fuel and the engine doesn't start, however, based on your original post where you stated the engine does run but idles too high, I think the excess fuel observation could be misleading.

First, pull the vacuum hose off the fuel pressure regulator. If there's fuel in the hose, the regulator is leaking and must be replaced. This is fairly common on GM vehicles. It's unheard of on Chryslers and Fords.

Since the engine does run, start by looking for a vacuum leak. The engine speed won't go up very much from too much fuel unless there's excess air to go with it. While it's still cold, use a squirt bottle to spray water on potential areas where leaks are common. In particular, look at the intake manifold gaskets, and vacuum hoses. Pinch the hose to the power brake booster too to eliminate a leaking booster.

Caradiodoc
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Wednesday, March 17th, 2010 AT 7:34 PM
Tiny
HANDYA
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Ok, nothing is working, let me start from the top.

Mechanic advised that compression in one of the cylinders was not at the appropriate level, therefore head job required. Head was taken to the machine shop and replaced in the car. Car is not starting. When the spark plugs are removed, and the key turned, gas flows through all the spark plug holes as though a compression pump is turn on. Once spark plugs are replace, engine locks.

Hopefully this will help, in getting the problem resolved and the car starting.
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Saturday, March 27th, 2010 AT 12:36 PM
Tiny
CARADIODOC
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Sorry for the delay in replying. My Verizon e-mail service is down for maintenance going on two days now. I am not receiving automated messages that you posted another comment. Hopefully that will be fixed soon.

Do you mean to tell me the injectors are sparaying constantly? That's a bad thing, but it might be a good thing as far as finding the problem. They are supplied with 12 volts on one wire, then the Engine Computer grounds the second wire to fire them. Unplug the injectors. If they continue to squirt fuel, they have to be stuck open. Not sure how that could happen to all of them. Just to verify, you do have four injectors, right? Not a single injector in the throttle body. Are all four cylinders loading up with fuel or just some of them?

If they stop spraying fuel when they're unplugged, there are only two possibilities. The return wires going back to the computer are grounded or the computer is grounding them. Verify there is 12 volts on one wire in one of the injector connectors. Use an ohm meter to measure the resistance to ground of the other wire. It should read open circuit, or very high resistance. If it reads low, look for a wire or harness that got pinched when the head was reassembled.

Caradiodoc
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Sunday, March 28th, 2010 AT 9:23 PM
Tiny
HANDYA
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The car is now running, except it vibrates and or shakes a little bit, when in park. At the stop light, and while your foot is on the brakes it does the same thing and feels as though it will cut off, but it doesn't.

What is required to address.

On another note, the mechanic advised the the ekg valvue (I might have the wrong name, but it sounds something like that) needs to be replace as the engine light comes on while driving but the car runs ok.
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Tuesday, April 20th, 2010 AT 7:29 PM
Tiny
CARADIODOC
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Hmm. So what fixed the constant pumping of fuel? The valve you're refering to is the exhaust gas recirculation (EGR) valve, but I like your name better. It introduces a little exhaust into the fresh incoming air. That displaces some air and fuel to make the engine appear smaller for a little better fuel mileage, but it mainly lowers the temperature of the burning fuel to reduce oxides of nitrogen. That's more common in diesel engines which run at much higher temperatures. The Nox is a contributor to acid rain.

The EGR valve opens only under certain conditions when you won't notice it. One time it must never be open is at idle or low speeds because you will feel the symptoms you described. The valve can get stuck open or a piece of carbon can break loose and hold the valve open a little. You will never feel it if the passages become plugged with carbon but by the '96 models, the EGR flow was monitored by the Engine Computer so problems with the system will be detected.

There are other things that can cause rough running but anything that causes the Check Engine light to turn on should be addressed first.

Caradiodoc
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Tuesday, April 20th, 2010 AT 8:21 PM
Tiny
HANDYA
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Do I need to take the car to the dealer to have it hooked up on the computer to determine the problem?
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Thursday, April 22nd, 2010 AT 8:38 PM
Tiny
CARADIODOC
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Not necessarily the dealer. Most reputable independent shops will have aftermarket equipment that can access the Engine Computer. GM is by the worst company at making their information available to aftermarket equipment manufacturers. By law, they have to release information related to anything that can affect tail pipe emissions. That includes the engine and transmission computers. Equipment manufacturers have to reverse engineer and figure out the rest of the potentially 47 different computers, and that can take years. Chrysler and Toyota make everything available to everyone except their security systems. Only Hyundai releases everything.

There may be a few things the independent shops can't do with their equipment but they will be able to read and interpret the diagnostic fault codes, and erase them to turn off the Check Engine light. They will also be able to read live sensor data while the engine is running. Some of the better equipment also gives the ability to perform actuator tests such as firing individual injectors and turning relays on and off.

Of course the dealer can do all these things too.

Caradiodoc
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Friday, April 23rd, 2010 AT 7:39 AM

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