Air conditioning problem

P0300 Random misfire - lean condition , vacuum leak , low fuel pressure , fuel filter plugged partially , mass air flow sensor .
If the misfire is random, check for the following conditions:
?€¢
System Grounds: Ensure all connections are clean and properly tightened.

?€¢
MAF: A Mass Air Flow (MAF) sensor output that causes the PCM to sense a lower than normal air flow will cause a lean condition.

?€¢
Air Induction System: Air leaks into the induction system which bypass the MAF sensor will cause a lean condition. Check for disconnected or damaged vacuum hoses, incorrectly installed or faulty crankcase ventilation valve, or for vacuum leaks at the throttle body, EGR valve, and intake manifold mounting surfaces.

?€¢
Fuel Pressure: Perform a fuel system pressure test. A faulty fuel pump, plugged filter, or faulty fuel system pressure regulator will contribute to a lean condition.

?€¢
Injector(s): Perform injector coil/balance test to locate faulty injector(s) contributing to a lean or flooding condition. In addition to the above test, check the condition of the injector O rings.

?€¢
EGR: Check for leaking valve, adapter, or feed pipes which will contribute to a lean condition or excessive EGR flow.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

The most common problem is low Freon levels. There is a low pressure switch which can be bypassed for testing, to see if the compressor clutch will engage or not.
You will need a pressure gauge later on, and some refill cans have built in gauges which come with them. The better way to do this is using proper gauges called "Manifold" gauges. Some may be borrowed from major autoparts stores.
The rule of thumb is that the system should not be contaminated with outside air containing moisture. A low pressure condition may be Restored by adding Freon with leak stop. But an empty system needs to be Vacuum pumped to eliminate moisture. A badly drained system may need compressor oil too.
Leak stop can help some systems, especially if the leak is on the low pressure side. There are gauges called sniffers, which can detect a leak. There are also chemical leak detectors for about $20 having ultraviolet light and glowing detector dye.
While this all may sound vague, it amounts to having a small leak that can be helped with leak stop and catching the problem before the system is completely drained. Every case is different.
Figure that you do not know when the leak started. If it was 5 years ago to run empty is different than 5 weeks or 5 days to lose all the Freon. The smaller the leak, the better chance that stop leak will repair it.
There are some CD's at Autoparts stores which will explain the repair process.
Also take into account that some techniques discussed in earlier times used $3 cans of Freon for testing. Today each can costs $7 to $17 and a car uses 3 or more cans for a refill.
So bypass the low pressure switch with a wire loop, then use leak detector with a leak stop before topping off the system. Look for leaks. If none are found, use the gauges and add Freon.
If you suspect the Low pressure switch is bad, then it is easily replaced without discharging the system.
I hope my info helps you.

Unfortunately, if you can't trace the flow of the fluid back to its source, you will need a specialty tool to do this yourself. I can tell you what a mechanic will do as part of an evaluation.

A mechanic will first use a kit similar to this Craftsman set:
http://www.sears.com/craftsman-cooling-system-pressure-tester/p-00946342000P

Essentially this works by attaching an air pump (like a bicycle tire inflator) to where the radiator cap fastens. By forcing pressure into the system, it will cause (hopefully) fluid to spurt out of small pinholes or around seals where it is leaking. After pressurizing, the mechanic will look with a flashlight.

The second part of the test is to dump a ultraviolet dye into the system and run the car to circulate it. After waiting for a bit of the dye-antifreeze to flow out wherever it is, the mechanic would then use a black light to trace the leak.

If you have access to a pressure testing kit or dye, you might be able to do this yourself, otherwise a leak test runs around $30 to $40 at a standard mechanic.

Hi there:
What can happen is the vehicles Freon will leak out and reduce the total pressure in the system. Then the low-pressure cut out switch will disengage the compressor when the low side is detected below 25 psi.

This safety feature is to protect the compressor itself. I have seen mechanics bypass the low cut out switch for testing. This should never be done and is not recommended.

The visual presence of oil around a fitting or pressurized line is a strong indication of a refrigerant leak. So my first step in air-conditioning leak diagnosis is to perform a very careful visual inspection of the entire system.

Although this is always my first step for diagnosing Freon leaks it is not always effective in finding the exact problem. In fact, this visual inspection will only uncover large to extremely large leaks. A more common air-conditioning problem would be small leaks that allow Freon to escape over long periods of time. So to follow will be some methods to detect these small leaks.
- The Robinair leak detector is a hand held battery operated electronic leak sniffer. The test probe on the end of the leak detector is moved about 1 inch per second in the areas of suspected leaks. The Robin air leak detector has an alarm that will go off when it detects the presence of a Freon leak. Note on some other models they may have flashing lights or a buzzer. Also some leak detectors are specialized to detect only certain freons (example: 134a) but they all are designed to alert you when they sniff the refrigerant.
- To find refrigerant leaks using the fluorescent tracer system, you first have to install the fluorescent dye into the cars air-conditioning system. Always follow the instructions and do not install too much dye! Too much can reduce the cooling efficiency of the system. Different refrigerant dye leak detectors will accomplish this in different ways. The system we use at work has a device that looks like a caulking gun, and a hose that connects to the low side fitting. Then you actually push the dye into the low side with the engine running and the compressor engaged. Next you run the air-conditioning system for several minutes to distribute the dye evenly. Then you put on your yellow glasses and examine the system with a fluorescent light.
The fluorescent dye shows up easily wearing the yellow glasses.

A very popular selling item is Refrigerant with leak sealer. This item will only seal very small leaks. I have used the stuff pictured to the right "super seal pro" and it does work in some situations.

The Freon leak sealer works best when you have low side system leaks. And if you happen to have a small leak from an O-ring on the low side this stuff works well. If you have a leak on the high-pressure side chances are this sealer will not work for you.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day

Could be the evaporator, rare but possible. Double check the schrader valves on the high and low pressure lines, and the shut off valves on the lines going to and from the condensor, and the condensor itself. (common culprit) Also the front seal on the compressor if leaking will have oily residue all over. No offense but try a different mechanic. Sometimes a new set of eyes works wonders!! Your mechanic won't be offended. If he is, fire him.

First things first.....You must have the air conditioning system hooked up to an a/c system machine and then checked for leaks and also read low and high side pressures. If there are leaks then low Freon (R134a) content and low refrigerant oil can cause the a/c system to not engage the a/c compressor which basically means you will not have proper defrost functionality nor regular air conditioning. Most shops, when working with your air conditioning, will install air conditioning dye to assist them in locating leaks and is the first step in diagnosing all a/c systems. Post the findings after thw

system must be tested for leak and repaired. The shops use a dye to find the leak. check your yellow pages under automotive air conditioning for shops that can service your air conditioner.

if it is low then you can usually put dye in the system to find a leak. go to local parts store, ask for a/c leak detector dye, read instructions on bottle. after you run it for a few days then check it under a black light. usually a hose.

you should have someone leak check the system with dye and gas sniffer. the most common problem with these jeeps is the evaporator leaking.

check pressure it may have leaked out already, also pressure test will tell if compressor is bad or other leaks, u can put dye in system and look for leaks yourself availible in most part stores, look at front of vehicle and look at condesor and see if any obvious damage