hi, i just bought a used 95 neon highline and it has a rough idle. i figured it could be a clogged injector so i put some STP fuel injector cleaner in and i noticed i can smell unburnt gas when the vehicle idles so i no longer think its that. i had a mechanic look at it and he found that cylinders 1 and 2 had a weak spark and unpluggin them from the coil while it was running didnt change the idle much so i changed the plugs and it didnt change, so then i did the wires and that didnt fix it either, i then got a coil from a low mileage neon at the wrecker to try and save money and its no different. does anyone here have any suggestions that i could check? also, all four injectors read 12 ohms like the haynes manual says.

 

check the compression. if i remember it should be at around 180 190 and no more than 10% diffrence from each other cyclinder.

 

that shouldnt cause a bad spark tho which is the problem we found by pulling the plugs off while it was running

 

i also found on another forum that it could be the cam position sensor could be the cause for the misfire. i had an oil leak near it that i thought was from the valve cover gasket but it may be from the sensor instead. could that be the problem?

 

i figured i would try disconnecting the fuel injectors one at a time and #2 cylinder didnt change at all so i am now lead to believe that the injector or the wiring is faulty. is there a way to figure out which one it is? can i clean the old injector instead of paying over $200 for a new injector?

 

someone awhile back said they soaked their injectors in seafoam overnight. and I would try to swap injectors to another cyclinder to see if it misfires because of the injector. and I would still check the compression, since it is an easy task on the Neon.

 

Nowhere in any of your posts did I see where your mechanic checked to see if there were any error codes in the PCM. Not all codes cause the check engine light (CEL) to come on. If you have a parts store nearby, they will hook up an OBD-II reader and tell you any error codes that may be in your system.

If you have errors, post them here. Oil leaking around your cam sensor means you need to put a new oring on the sensor, but has no bearing on whether or not it works. All the cam sensor does is sense the magnets that are on the camshaft and the fluctuation of the magnetic field tells the sensor where in the cycle the cam is at. If it is intermittent, then an error code will be in the PCM. Also, misfires are stored as error codes in the PCM too.

The range of good compression per cylinder is 175 to 195, and yes, no single cylinder should be more or less then 10% of any of the others. You should also do a pressure leakdown test (in addition to a compression check) to see if your head intake and exhaust valves are sealing up properly.

You may also need to take a good long look at your IAC and TPS sensors. They really control idle more then anything else, and you may also have error codes indicating them as well in the PCM.

Finally, unless the coil you got from the JY tests OK (Haynes manual gives all the tests on how to check and the specs to check against), then you could have another coil that is giving out a weak spark. Doubt it, but it can happen.

 

i figured i would try to clean my injector with a can of compressed air, thought it may work, but i started the car just to make sure unplugging the injector wouldnt change the idle and after shutting it off and pulling out the injector it was wet so it is putting gas in. ive unplugged the wire while it was running and there is a spark.
The codes i was getting btw are:
12
22
i also found a way to check it with just the key and since the mechanics shop i got these 2 just the other day:
43
21(just recently)
also, when i check them with the key it flashes 43 twice, does it just go off the history and list them every time they come up?
i read somewhere to spray water on the coil and wires while its running to test the coil easily and i had no change doin that so by that method my coil is ok

 

If an injector is clogged, it is clogged with a mineral deposit that most likely will not come off with just a blast of air - but hey no harm should occur using just air if you are careful to watch out for the seals.

Spraying water on the coil and or wires will indicate if you have any cracks that may cause voltage leakage, but it will not indicate an internal failure of a component that controls how and when a particular coil will fire. That can only be done by testing the coil's resistance. The Haynes manual shows exactly what checks can easily be done with a multi-meter. Both are cheap if you don't have either one.

The reason you have two 43's is because you have two cylinders misfiring. You need to go to a part store and get the 4 digit error codes from the PCM to know which ones, but I bet its 1 and 2. The readout you will get is free. Autozone, Advance, O'Reilly, NAPA all do these for nothing and it takes about 1 minute to get the answers. They can even reset the PCM to clear out old codes. Of course, you can clear out old codes anytime by taking the positive post off the battery for 2 minutes.

Ignore error code 12 (and 55) 12 means the battery has been disconnected sometime in the last 50 on-off key cycles. 55 means no more codes (done).

However, the other two codes you mention will also affect your idling. Error code 21 means you have an O2 sensor going/gone bad. Usually it is the upstream O2 sensor (the one directly under the air box on top of the exhaust manifold). The 4 digit error code in the PCM will tell you which one for sure.

Error code 22 indicates that your temperature coolent sensor may be going/gone bad. If it reads too low for too long, then the PCM thinks the motor has not properly warmed up and will run it more rich (think of it as choked) until it gets to the proper temp. This has also been known to affect engine idle (again, it is running too rich for too long).

So. Go to your nearest parts store and get the 4 digit error codes. Buy the O2 sensor (about $60) that is indicating a problem (if has been over 60K since it was replaced, it is due for replacement anyway). A new temp coolent sensor is $11, go ahead and get one and replace yours.

As for error codes 43, they are your biggest worry. Misfires can be caused by a bad/intermittent cam/crank sensor, and loss of compression would not be a cause for error codes 43. You may still have clogged injectors, but you need to soak them in cleaner to remove those deposits - or take the whole fuel rail with injectors to a shop that can clean them professionally.

HTH

 

alright, thanks for the help. the coolant sensor one was the only one for a long time and it would just happen occassionally at weird times. i would start the car and it would be on, i would drive home and it would come on after bout 10 min but not come on for 3 days prior. but ill look into the coil and find out y this misfire is occuring. thanks again