okay I need a bit of help here. I've got a 2001 3.8l v6 mustang a while ago my wife was driving it and the engine light came on. Code was for a misfire in cylinder 3, I replaced the plug wires, and ignition coil. The problem went away for a while. I started driving it and after about two months of driving it the cylinde 3 misfire came back again. I replaced all of the plugs and th problem went away for about another month. The problem came back so I replaced the fuel injector, but, no improvement. You can feel it stumble between 1200 and 2500 RPM, the car has horrible power going up hills. I need some help on this, I'm kinda a newbie to working on cars so please take it easy on me. Thanks.
Misfire issues
- Thread starter ctuck58
- Start date
wmburns
SN Certified Technician
First, did you follow the factory routing for the spark plug wires? Use all factory standoffs and looms? Are the spark plug wires touching any metal parts?
Try this old racer's trick. Run the car in a totally dark location. Look for the blue hue of escaping spark. Inspect the wires for white spots which is evidence of arcing. Arcing doesn't take very long to ruin a set of wires.
When was the last time the MAF was cleaned? PCV value replaced? Fuel filter replaced?
Also, excessive EGR flow can cause this symptom. Try disconnecting and plugging the EGR vacuum line. Does it improve?
Try this old racer's trick. Run the car in a totally dark location. Look for the blue hue of escaping spark. Inspect the wires for white spots which is evidence of arcing. Arcing doesn't take very long to ruin a set of wires.
When was the last time the MAF was cleaned? PCV value replaced? Fuel filter replaced?
Also, excessive EGR flow can cause this symptom. Try disconnecting and plugging the EGR vacuum line. Does it improve?
Fuel filter is due for a replacement. I'll fix that tonight. I haven't noticed any white spots on the plug wires, but, admittadly I broke a few of the standoffs and clips when I changed the wires the last time. I'll get new ones and check for any arking tonight. The MAF and PCV valves have never been replaced or cleaned. Sounds like I've got a bunch of work to do. Also, to clarify another symptom, once the engine gets to about 2,200 RPM the problem seems to get a little better. It doesn't sound like the system is starving for gas ( I would think that restricted fuel flow would show up through the whole operating range, correct?)
Anyway, I'll try what you've suggested and let you know how I make out. Thanks.
Anyway, I'll try what you've suggested and let you know how I make out. Thanks.
Update - Still have misfire
OK here's where I'm at...I've changed the fuel filter. Checked the compression, all cylinders are within a 2-5 psi of eachother. I checked the vacuum and it holds steady at about 19 inches (doesn't bob). Re-checked plugs and wires, put spark test light on and cyl 3 is getting spark power from coil pack.
I have read that the engine light will blink when a misfire is actually occuring and stay on and solid until the code is cleared, correct? If that is the case then the cylinder only misses intermittantly and usually under load (like going up a long hill). I'm noticing no smoke, I do smell a little more exhaust than I should but I think thats because my exhaust pipe is rusting out near the muffler. I'm really confused at what this could be at this point. Any other thoughts???
OK here's where I'm at...I've changed the fuel filter. Checked the compression, all cylinders are within a 2-5 psi of eachother. I checked the vacuum and it holds steady at about 19 inches (doesn't bob). Re-checked plugs and wires, put spark test light on and cyl 3 is getting spark power from coil pack.
I have read that the engine light will blink when a misfire is actually occuring and stay on and solid until the code is cleared, correct? If that is the case then the cylinder only misses intermittantly and usually under load (like going up a long hill). I'm noticing no smoke, I do smell a little more exhaust than I should but I think thats because my exhaust pipe is rusting out near the muffler. I'm really confused at what this could be at this point. Any other thoughts???
wmburns
SN Certified Technician
Just wondering if you understand that with today's high energy ignition systems that IF the spark plug wires touch metal objects and arcing occurs, this will break down the insulation and ruin the wires. So if damaged, simply correcting the routing will not fix the problem. Further, it really doesn't take log to ruin a set of plug wires if arcing occurs.
It's important to understand this because as you post back, the assumption made is that all of the previous items have been ruled out. Therefore, each trip back to the well is likely to get more esoteric possibilities. The resultant wild goose chase is a waste of time and resources.
Your problem could be arcing to #3. Just checking for spark does not rule out arcing. Further, it would be expected that a marginal spark plug wire would be more likely to misfire under increasing load.
Since you stated that a few of the clips were broken, this brings up the possibility that a bad spark plug wire is the source of your problem. Consider replacing it.
In answer to your question about the check engine light. The light blinks when a misfire is actually occuring. If engough misfires happens that emissions levels are no longer being met, the check engine light is "latched" and the DTC code posted.
Have you done the EGR test?
It's important to understand this because as you post back, the assumption made is that all of the previous items have been ruled out. Therefore, each trip back to the well is likely to get more esoteric possibilities. The resultant wild goose chase is a waste of time and resources.
Your problem could be arcing to #3. Just checking for spark does not rule out arcing. Further, it would be expected that a marginal spark plug wire would be more likely to misfire under increasing load.
Since you stated that a few of the clips were broken, this brings up the possibility that a bad spark plug wire is the source of your problem. Consider replacing it.
In answer to your question about the check engine light. The light blinks when a misfire is actually occuring. If engough misfires happens that emissions levels are no longer being met, the check engine light is "latched" and the DTC code posted.
Have you done the EGR test?
acsthacker
New Member
Just my two cents worth if you haven't figured out your problem yet, but couldn't a bad (or one going bad) coil pack possibly cause a misfire occasionally?
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