just wont run right!!!!! 2001 cylinder 4 misfire

[bradw18]

i just got a really good deal on a 2001 lincon ls v8 model. when i got it it had a misfire i took it and put it on a scanner and it read bank 1 lean bank 2 rich or the other way around i dont remember and misfire on cyl 2 and 4 i read on all the fourms about the cops going bad. well i replaced both of them and i put 2 new plugs in the 2 cyl that were misfiring. and while i was at it i checked the plugs that were in it and they wernt oil fauled or anything like that no signs of leaking valve covers. got it all back togeather erased the codes and drove it. still was misfiring. well scanned it again and it only came up as cyl 4 misfire. still to lean and rich. i pulled the coil out and put a extra plug in it and grounded it. started the car and it was sparking. so the coil and plug are good. i even pulled the injector out of the cyl that is misfiring switched it with another injector erased the code and guess what. still misfireing. im out of ideas. i bought a hand held scanner and a compression tester. i am out of ideas when it comes to this car.

PLEASE HELP

[bradw18]

at a idle you can feel the car misfiring. but when your driving you dont really feel it. and the exaust smells a little rich.

[shorod]

Welcome to the forum!

Hopefully you are not discovering why you got such a good deal on the car....

Have you tried the compression tester yet to confirm cylinder #4 is close to having the same compression as the other cylinders? What brand of spark plugs did you install? Are you sure you are counting cylinders correctly? Cylinder #4 would be the passenger side nearest the firewall on your V8.

-Rod

[bradw18]

yea fords go from the passenger side 1234 then driverside closest to the fan 5678 right? is loss of compression a commom problem with the 3.9?

[shorod]

You're correct on the cylinder numbering. I wouldn't say it's common for the 3.9L to have compression issues, but it's easy to check on this installation and inexpensive since you already have the tester. Ruling things out is important when trying to troubleshoot these types of issues.

-Rod

[bradw18]

just did a compression test on cyl 2 3 and 4 were all above 170. those are the only 3 i did a compression test on. i thought for sure i wouldnt have any compression on number 4. would the compression test read low if a valve was sticking shut? but if that was the case the motor would be making some kind of noise wouldnt it?

[danielsatur]

Make sure the fuel injector signal + ignition signal wires to the COP cylinder 4 are getting good continuity signals,
the copper wire could break inside the insulation.

Also make sure, there's no extra fuel injector seals in the fuel rail going to injector 4.

[bradw18]

does the rubber line going to the passengerside fuel injector rail just disconnect or pull off? thats for the suggestion about the clogged fuel injector rail. how would i check the contunity of the injector conector? i ohmed all the injectors them selfs and the ohm at 11 to 12 ohms. a bad sensor would cause a random misfire would it? thanks all of yall for all the help. i really hope i can figure this out.

[bradw18]

i just went and sepent 68 on a new injector im gonna try replacing number 4 and blow the fuel rail out with compressed air real good and make sure theres nothing clogging it up.

[bradw18]

put the new injector in and guess what????

still misfire hahahhaha


before doing that i relieaved the fuel pressure and took the number 4 injector out. put a cup under it and turned the key and a lot of gas came out quick so i dont think clogged.

installed the new injecor put it all back together and it still misses. i put my scanner on it and did the live data stream. it showed

fuel system 1 cl
fuel system 2 cl -fault ????
calc load percent 35.69
ect temp 165
stft b1 percnt 4.69
ltft b1 percent -19.53
stft b2 percent 14.06
stf b2 percent -19.53

[shorod]

You're correct, a valve that was stuck closed would cause the engine to make noise.

Since you had previously swapped injectors around according the post #1 above, I'm sorry that you purchased a new injector. The fact that the misfire remained on #4 even with the injectors, plugs, and COP should have been an indication that the injector is not the problem. At least now you know that the fuel rail is also not the problem and is providing plenty of fuel to the injectors.

Your long term fuel trims suggest rich mixtures on both banks over the long term (double check your numbers for bank 2 above), but the STFT on Bank 2 indicates the PCM is attempting to compensate for a really lean condition on Bank 2. The STFT for bank 1 though looks to be okay. Maybe the problem isn't cylinder #4 afterall....

During the datastream how were the oxygen sensor responding, both sensor 1 and sensor 2? Does your scan tool give you the option to monitor the cylinder misfires real time?

-Rod

[bradw18]

scan tool isnt that good lol. i was looking and what the cl fault ment closed loop fault o2 up stream i switched the 2 up stream 02 sensors around thinking it would change the error to the other bank but it didnt help. it still showed miss fire cyl 4. iv about had it with cyl 4. when i looked at the 02 sensors they appeared to be factory. would the 02s cause the misfire like it is? sending the computer wrong signal there for sending ot much fuel to the injectors and causin misfire? that would explain the rich smell coming form the exaust.

[bradw18]

stft b2 percent 4.06 typo

[bradw18]

i thought about what you said the o2 sensors are just picking up on what the motor is telling it. the down stream 02s dont deal with the fuel managment do they? theres got to be another sensor making the bank 2 lean. my scanner only does freez frame data. it wont do the live data streaming.

i did a fuel pressure test and its about 30 or 40 maybe a little more.

[danielsatur]

Check the spark plug boss on cylinder 4 for water contamination, we have seen bad COP covers leaking water thus causing misfires.

The upstream O2 sensors gives a feedback signal to the ECU for Air/fuel mix, the engine is still missing on cylinder 4 (bank 1)!

Did you Reset + clear code, after COP replacement?
Was there a rust residue on the original COP's?

Tran
4 8
3 7
2 6
1 5
Fan

Bank1 = cylinders 1-4, and bank2 = cylinders 5-8.