QuestionQUESTION: I have a 95 neon single overhead cam 2.0 with 170,000 miles that will be running just fine and then cut out for a second or two sometimes longer and it has even completley stalled. When it does this I have checked the codes using the on off key method and it always comes back 12 43 43 55.I know that the code 43 is a multiple missfire code. I had this happen about 6 months ago and found that I had a bad plug wire and replaced the plug wires and plugs and the proplem went away but now its back. I tried replacing the plug wires again but the problem is still there. I checked the plugs for carbon tracks but they all look good, and there is no oil leaking in where the plugs screw into the heads. I have checked the resistance on the coil pack and it is where it should be within the specs of the manual that I have. I have also checked the connections on the pcm and they are clean.I have also tried to make the car missfire by moving and wiggiling all the wires going to the coil pack and the pcm with no luck. The other strange thing about all of this is that after it throws the code 43 when it acts up and I get to where I'm going and I shut the car off and restart it the code has cleared itself and is gone.The missfire happens very randomly sometimes when I first start out when the car is cold and sometimes after I have been driving for awhile and the car is good and hot. Any thougts on what I might be dealing with here would be greatly appriciated. Thanks
ANSWER: Hi Ned,
It appears that you have looked into the electrical possibilities for the multiple misfires. The other areas are: injectors, and mechanical engine problems,and the pcm itself. You might begin by doing a vacuum gauge reading of the intake manifold to see if it is steady or not, at what level if steady, and by what variation if unsteady which my be a clue about mechanical issues. Let me know what you find and we can discuss it from there. Also doing a compression test when the engine is warmed up to see if the values are at least 100 psi and within +/- 25%. Finally, check that the timing marks on the cam sprocket lines with the mark on the rear cover at TDC for cylinder #1.
Roland
PS You might also check to see if the spark plugs are of even wetness as an evaluation of the injectors. Also check the pcv valve, and also check the egr valve to be sure the the valve stem doesn't appear to show the valve is sticking in the ajar position (spring action should close it tightly, if not lube it with WD-40).. Sorry to give you so many things to check.
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QUESTION: I do not have a vacuum gauge so was unable to check vacuum readings. What I did find was pcv valve that had probably never been changed. Where the hose connects to the motor was clogged,the hose had a hole in it, and the pcv vale was very gummed up but still working. I cleaned out the clog and installed a new hose and pcv valve. Could something as simple as this be causing a code 43 which is an electrical misfire code as you know. The egr appears to be closed all the way but I don't have a hand vacuum gauge to check it according to the manual, any other way to check and make sure its working correctly? I drove the car for about 25 miles and it didn't act up but I'm still not sure if its fixed. I do have a compression tester but have not checked it yet. Do you think I should continue with checking the vacuum and compression or do you think the bad pcv situation could have been causing the problem?Thanks again
ANSWER: Hi Ned,
Yes the PCV system being blocked could cause the misfire. You can disconnect the battery for a few minutes to erase the previous 43 code. Then drive it some more and recheck the codes, using the ignition key:on-off-on-off-on and leave on, doing that in 5 seconds or less. Then count the flashes of the check engine light. If you only get two sets of 5, a 55 code meaning "end of readout". then your problem is solved. Otherwise we can go on from there. As long as the egr seems to be firmly closed by the spring action to a dead stop it should be OK. So hold off on any further testing.
Roland
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QUESTION: Hello again, unfortunately the problem reoccurred and I bit the bullet and took the car in and had a complete diagnostic test done and of course the car did not act up for them and all they could tell me was that there was a code set for coil driver cyl#1&2 code 43. This leads me back to the coil pack itself even though it tests ok could this still be my problem and if not any other thoughts on what the problem might be? I have been driving the car for 4 days now since I had it checked without any problems.Thanks again
AnswerHi Ned,
I would check the coil driver circuit, which is a different code than a 43. I will get back to you with the instructions for doing that later today.
Roland
Hi Ned,
To check the ignition coil and the wiring from the powertrain controller to it, both of the driver circuits, just to be sure, and to verify that they are or aren't alike:
Begin by removing the coil's plug. Measure the resistance between the center pin of the coil socket and each of the outside pins. The resistances should be very nearly equal and should be less than 2 ohms. Leave the coil unplugged.
Then remove the plug at the powertrain that has pins 1-40. Look closely at the plug and notice pin numbers next to each wire. Measure the resistance to ground (any point on the engine that is clean and shiny) of pins 2 and 3 of that plug. These both should be infinite. Then measure the resistance from pin 2 to either of the outside contacts on the disconnected plug at the coil On one it should be infinite on the other it should be 0, then do the same on pin 3 and you should get the reverse result.
You might try flexing the wire harness while you do all these measurement on the pcm plug just in case there is an intermittent open or short condition.
If you find everything to be equivalent on both sides of the coil, and its plug/wire interface to the PCM then you have the choice or replacing the coil (which could be flaky but not reveal it under static conditions), or replace the PCM which is much more expensive.
This would be the conclusion to draw if as you were told by the shop that you got a true coil driver fault code, which is p0351 or p0352.
Because there is no check engine light code for these faults you could very well have on or the other and not get a fault code using the ignition key.
I will be interested to know what you learn.
Roland
