I will go through the entire problem I had with my car that, all of the sudden began to misfire. In actuality, it had this mis years ago and is the reason I parked it. Had it sitting for at least 4 years until cat i was using took a dump. Symptom was, after driving all day long, at one certain left turn, going home, would stall out and use to trip me out because of of the possibility of getting stuck in a busy intersection; not fun.
I have a 1996 Cirrus and will go through how I found this mis, which may not be the cause of all misses in these cars. I will include photos and video links and will show anyone who wants to fix it themselves to save themselves a great deal of money because if I had someone else do it like a mechanic or shop, would have spent more than the car is worth. Just tested my fix today and it works now with no sign of a misfire at all.
Will take you through the dead-ends I went through and money that went down the drain as well. From a failed pump that mechanics removed the filter sock because I believe was interfering with fuel gauge level since the float is very close to the sock filter and I learned many years later, cause the fuel pump inlet to become clogged Youtube video that shows this condition . Please take a view at this video and see what happens when unscrupulous mechanics do to get something "fixed." A clogged fuel pump as this one would certainly starve the engine of fuel and cause stalling. A fuel pressure abnormal reading would have caught this. It is a process of elimination of what could be causing a misfire or any other problem for that matter. Unless you have access to oscilloscope, it becomes more of a guessing game as what is causing a problem. Most of us do not have an oscilloscope so there must be a methodical manner in which to attack a problem.
I took the hit and mis approach and will pass on the knowledge gleaned and want to pass it on to those who are having a problem with these cars. I wll go step-by-step on the problem involved and the steps I took to resolve it. As mentioned before, car had a misfire only after having driven it for a whole day and would misfire when driving home. Needed the use of another and only had the Cirrus decided to run it after having had it sit for at least four years do to the misfire. History on the car, bought it with 36,000 on it. Failed fuel pump 3 years after I bought it. Ran pretty good for a while. After having it started in years, it seem to run o.k. but one day it just stopped running. This happened to me years ago and found out it was the fuel pump went bad (or so I thought: watch Youtube video above at the link) and find out what it really was. Having sprayed carb. cleaner into the intake and it ran for a few seconds so this pretty much confirmed it was the fuel pump. I took it upon myself to replace it. Got a used pump at the salvage yard and dropped the tank and replaced the pump which is no easy task. After having replaced fuel pump, it did run and all was better.
Driving it around a bit the misfire problem crept back in. Changed the spark plug wires, spark plugs (both needed to be changed, bad quality ones and corroded because of sitting for a while; changed the crank sensor (also no easy task), changed distributor, cleaned out the Idle Air Control, cleaned the EGR tube, EGR had been replaced not too long before I sat the car so I would assume it was not the EGR. Nothing solved the misfire. The process of elimination continued and there was oil in the spark plug wells but not drowning in oil but had the rear oil seals at the valve cover changed to eliminate the possibility that oil in the spark plug well would cause a short circuit of the spark plug firing. This, too did nothing to take care of the misfire. Was getting to the end of eliminating things in the car.
02 sensor was a good idea to replace anyway since I had it replaced with a Bosch unit at a tune-up tears back but found out that Bosch 02 sensors may not work well on some Chrysler's, as well as Bosch spark plugs. I did not expect this this to fix the problem but just something I wanted to do since learning Bosch may not work; replaced with OEM unit by NTK, a division of NGK. If you have changed the plugs or wires on these cars, you will very well know that the upper intake manifold must be removed in order to reach the rear three plugs and wires under the intake. Although it is not easy to do this, it is not a difficult as other maintenance on these cars so you can do it with general tools.
Now I will get to what was causing the miss in my car which became clear o me after taking off the manifold so many times to change the wires, distributor, oil seals and all of which was not done at the same time since I was unsure what was causing the problem. Since I am quite tall and not having any place to balance myself on the engine when working on the rear of the engine, I by mistake, placed quite of bit of pressure on the fuel injector wiring harness which looked o.k. but I did notice that it was hard and brittle. Having ignored this and putting the engine back together I left it as is. After driving car henceforth, the misfire become worse. A-ha! Decided to remove the fuel injectors since they had over 200,000, I thought it would be a good idea to service them by having them cleaned and since I was going to investigate the brittality (is that a word?) of the harness and have the manifold off once again, there I went. Slowly removing the harness and disconnecting from the top of the valve cover, it was obvious that the harness has seen much better days. Took an ohmmeter to to each of the wires, it was obvious once again that the high resistance I encounter would be a big problem. Should have suspected the wire harness was damaged and needing to have it replaced since I did see once bare wire which could cause a short but I has decided to ignore it then. This was my downfall.
To go on, after removing suspect wiring harness from the connector and from the car, there is a four pin connector; one pin being the ground and the other three wires going to the injector from the the computer. The readings I was getting as I tested the wires was unbelievable and of varying resistances, 13.0 ohms here, 9 ohms there, I knew I was nearing the problem of the problem. Decided to try my hand at rebuilding the harness since I am that kind of guy. I know how to solder and embarked on the task of rebuilding the harness which I will take anyone through the process if they so wish to do. after stripping back the layers of tape on the harness, the wires were in terrible shape, all dried up and stiff; they did not look good and were in need of replacing. Will include of before and after pictures and video of the offending part will be assembled and featured for your amazement and curiosity when I am able to get around to it which wont be long. After resurrecting the harness and checking the resistance, which was 0 ohms :-)! And after having the fuel injectors back from their cleaning, I installed the harness, and reassembling the manifold and associated parts, I took it for a spin today, Viola! Misfire eliminated and car is running great. There it is. The rear fuel injector harness for the hard-to-reach three to the rear is located in an oven-like environment that no set of wires are supposed to be subjected to long periods of time without checking their condition and replacing them if needed. This is what I found out. The harness in the front three does not get subjected to so much heat as the rear so they are more usually in better condition; although, it is a good idea to check that wiring as well. There is some good news in all this. One does not need to disassemble the engine to get access to the wiring harness to check for its integrity. The connector for the rear three injectors is located between the power steering reservoir and upper intake manifold and can be disconnected to access the pins where on one can check for their resistance. If they have any resistance at all and your car is misfiring I would suggest the harness be rebuilt or replaced with a better unit, not necessarily new, but a better used model to save on money. If anyone would like me to take them through any one of these fixes and checks, please feel free to ask my and I shall respond. I want all those who have been racking their brains to regain the peace of mind one gets when their car will not stall out on them while driving home and always having to fear driving their car because of this problem. I welcome any and all questions and I hope that this helps at least one other car owner.