misfire after new injector.

[nickb123]

A few days ago I finished installing new injector O-rings on the passenger side and 1 new injector on the 2nd cylinder back on the passenger side on my 99 5.0. I had to remove the upper intake to get at the injectors. After I got everything back together I started it and let it idle while I checked for fuel leaks. I didn't see any and the engine seemed to be running good. But when I put it into drive I could tell right away it was running on only 7 cylinders, So I parked it. I checked the plug wires because I removed the coil packs and everything seemed in order there, then I check to see if all the injectors where plugged in, I confirmed 6 where, (I couldn't see the rear 2 on the drivers side.) When I had it apart I disconnected all the injectors because I was going to do the o-rings on the drivers side too, but I didn't and just plugged the wires back in. It ran fine before I fixed the fuel leak, I had to replace the injector because I damaged it removing the bottom O-ring. So what could be my problem? Is the computer not use to the new injector or something?

 

[Birdy]

Which cylinder is misfiring? And if it's the one one with the new injector, did you remove the little rubber boot over the nozzle? I know it's kinda a dumb question.

 

[nickb123]

I dont know what cylinder is missing, how should I determine that? The new injector did not have a rubber boot, both ends where open.

 

[Birdy]

While idling you can unplug one injector at a time (or one plug wire)and which ever one doesn't make it run any different (worse) that's the one. Or if you have a laser heat gun, shoot the exhaust right at the head at each cylinder, and the cold one is the bad one, again while running.

 

[Turdle]

If it is mis firing and no check engine light is displayed, You can almost be certain it is ignition related.

First, does the check engine light display? You might need to drive it a bit to get it to turn on.

If you do see a check engine light, have the codes scanned and it will tell you which cylinder is misfiring.

Also, make sure the check engine light works by switching the key to on. All cluster lights should turn on.


Are you positive the injector you replaced was for a 99-up 5.0 explorer? Reason I ask, is, the earlier ones look similar, and will even seem connected. The connector will click into place, however inside the pins will not contact. That would account for a dead cylinder after replacing one injector.

 

[nickb123]

I will try to find the dead cylinder tonight. I will also look at the new injector and compare it to the old one, although I'm pretty sure its the correct one. The check engine light is on but was on before, for a o2 sensor. I disconnected the battery to see if the light comes back on for the misfire.

 

[nickb123]

I just went over to look at the car and try to find the cylinder that is misfiring. I unplugged the new injector and it ran worse so its not the new one. I also pulled the plug wire for the 3rd back cylinder on the driver side, that cylinder is good. Another thing I found out is do not pull off a plug wire while the car is running, I got shocked quite badly. When I started the car this time it ran very bad, it shook the whole car. Its almost like it had more than 1 misfire. So how do I find the bad cylinder if I cant get at the injector wires and removing the plug wires shock me? I didn't let the car run very long (less than a minute) so the Check engine light didn't come on yet. I feel like if I let it run long it would ruin the cats.

 

[budwich]

get a data logger (computer odbii interface) and see what the data is telling you, I do believe misfires are logged against each cylinder. If that's not available, pull the plugs (label them) and compare each, perhaps an "abnormal look" will tell you which one has a problem (might be wet, carbonned, otherwise).

 

[Birdy]

Agree with budwich, if you're careful you don't get shocked, don't touch the car when you pull it helps, and loosening the wires so they are just sitting on there before starting it helps too. I've also heard people use an insulated pliers.

 

[nickb123]

The spark plugs are new, they have at the most 300 miles on them, I used oem motor craft double platinum. Should I have pulled the wires off the coil pack instead of the plug? Are the ends of the plug wire that goes to the coil pack delicate at all? Could I have some how broke a connection at that joint?

 

[Turdle]

Please, stop what you are doing and have the PCM scanned for stored codes. If there is a misfire stored it will identify which cylinder missed.


Also, do not be so fast to forgive your brand new spark plugs and wires. Read this

http://www.explorerforum.com/forums/showthread.php?t=379383

 

[Birdy]

You should still be able to tell which ones not firing by looking at the plugs, and the wires shouldn't be that fragile, twist to loosen them first then pull, yea, it's usually easier at the coil pack.

 

[Birdy]

Sorry Turdle, Figured he'd have found the cylinder quick and easy.

 

[Birdy]

If driven enough the pcm should set a specific misfire code no matter the reason. I've had a bad injector, coil, spark plug, etc, and the thing always seems to know which cylinder.

 

[nickb123]

Please, stop what you are doing and have the PCM scanned for stored codes. If there is a misfire stored it will identify which cylinder missed.


Also, do not be so fast to forgive your brand new spark plugs and wires. Read this

http://www.explorerforum.com/forums/showthread.php?t=379383

The thing is, it ran very smooth after the new plugs and before I pulled the upper intake and replaced the O-rings on 3 injectors and replaced 1 injector. So I don't think the plugs could have went bad just sitting there. It would have to be related to the things I touched. Also I have not driven it and not let it run very long, so it didn't have enough time to store a code. I don't want to drive it when its running like it is now.

 

[budwich]

I wasn't blaming the plugs... they are used to tell you if a particular cylinder isn't working correctly for what ever reason.... there after (ie. once you have found the particular cylinder), you can then focus on that cylinder AND the associated "stuff" with it... that's all.

Further, you can "resistance check" your injectors to see if there MAYBE is an electrical condition that is causing your issue. All this is to save tearing everything back apart which of course, you can do a again... practice makes perfect...

Further, I think random misfires won't set a code unless it goes thru a "threshold" but I think on some vehicles there are viewable counters that will help you.

 

[RickOTR]

Had a problem similar to yours. I replaced the number 3 injector because it was bad, but ended up with with an even worse misfire. Did some searching and found that even the slightest difference in injector flow rates between injectors would make it difficult for the PCM to adjust them due to limited programing. Went ahead and bought 5 new injectors and that solved my problem. It is recommended when replacing injectors that they be replaced in sets.