[billabong]

After fitting extractors and new exhaust my 4.8 has developed a miss. It goes fine when you are up it, but misses up to half throttle under 2500 rpm. It's still very driveable, dut very annoying when you slowly apply the throttle.

It has been on a scanner and there are no faults coming up. I replaced the plugs yesterday to no avail. All coil packs look good and I have checked all the electrical joins I could find.

Any ideas?

 

[Notso]

Spark Plug leads?

Burnt Valve, unlikely!

 

[billabong]

It doesn't have leads, the coils are on top of the plugs. I hope it's not a Burnt Valve!

 

[billabong]

Any other ideas?

 

[ITS A FORD NOT A NISSAN]

oxygen sensor? if you replaced the exhaust

thats if it has an oxygen sensor mounted in the exhaust

 

[Patrol Junkies]

When the extractors are cold, start it, make it miss fire, shut it down, try not to let it run on all cyls, put your hand near the extractors, as they come out of the head and see which one is the coolest, lets say its pot 4 is coolest, swap coil packs with pot 5, test again, if 4 is still cooler swap sparkplug, double check everything, again.
Is it on Gas?

 

[4.2BeautUte]

The 02's are in the manifold so if extractors have been fitted the 02's would have had to have been installed into the extractors.. Seeings as that's whats changed I would start there. In saying all that I wouldn't have thought a faulty 02 would cause it to miss on petrol (might on gas) but you never know...

 

[rjhug1]

In saying all that I wouldn't have thought a faulty 02 would cause it to miss on petrol (might on gas) but you never know...

Totally agree. And a busted oxy sensor will throw up a plethora of fault codes and it will run so rich it will have plooms of black smoke pumping out the back as it goes into limp mode. Besides, O2 sensors control air-duel ratio's (in conjunction with the afm) and isnt related to spark which is what is sounds like.
Scan gauge wont tell you much and I didnnt think there was much to see by 'looking' at the coil pack. I had a similar thing happen on my old s15 200sx. At nissan, the software can isolate each cylinder and put it under load to see where the issue is. I would double check all plugs are torqued correctly and then isoltae which cyl in causing the issue. The changing of the exhaust at the timing is odd, by strabger co-incidences have happened.

 

[billabong]

oxygen sensor? if you replaced the exhaust

thats if it has an oxygen sensor mounted in the exhaust

There are 2 on the exhaust and they were replaced recently. My mechanic assures me if it were an 02 sensor, it would show up on his scan tool.

 

[billabong]

When the extractors are cold, start it, make it miss fire, shut it down, try not to let it run on all cyls, put your hand near the extractors, as they come out of the head and see which one is the coolest, lets say its pot 4 is coolest, swap coil packs with pot 5, test again, if 4 is still cooler swap sparkplug, double check everything, again.
Is it on Gas?

Ah yes. Good idea. When it is running rough at idle (about 50% of the time, but only when warm) I will try the squirter bottle with water trick on the extractors. Thanks, but I'm not real keen to touch them and it won't misfire until it's up to running temp.

No, it's not on gas.

Thanks for the suggestions guys.

 

[billabong]

At nissan, the software can isolate each cylinder and put it under load to see where the issue is. I would double check all plugs are torqued correctly and then isoltae which cyl in causing the issue. The changing of the exhaust at the timing is odd, by strabger co-incidences have happened.

It ran fine for a few days after the exhaust was fitted and I replaced the plugs with iridium on Friday. If I can't find the problem today, I will book it in at Nissan. Thanks.

 

[rjhug1]

There are 2 on the exhaust and they were replaced recently. My mechanic assures me if it were an 02 sensor, it would show up on his scan tool.

Absolutely, its one of the fundamental failures to throw a CEL. If you can get the thing to miss at idle, pull a coil pack one at a time off each cylnder. It will obviously run rough, but you should still clearly hear a miss over the top (or miss removed). That should be easy enough with a 6cyl, not so much with a 4.

My money is still on the pack. I dont know how changing manifold affects the spark, but any weaknesses will be exposed. I had the exact same thing on my old SR20DET.

 

[MelloTB48]

Did they make sure when refitting the o2 sensors that they were fitted to the correct bank of cylinders as one is for the from 3 cylinders and one for the back 3. i have seen this before were its trying to change the fuel ratio on the wrong bank of cylinders causing a miss. As for coil packs they will usually break down under load if they r totally buggers then idle also personaly i dnt think its the coil packs

 

[4.2BeautUte]

Did they make sure when refitting the o2 sensors that they were fitted to the correct bank of cylinders as one is for the from 3 cylinders and one for the back 3. i have seen this before were its trying to change the fuel ratio on the wrong bank of cylinders causing a miss. As for coil packs they will usually break down under load if they r totally buggers then idle also personaly i dnt think its the coil packs

Ah true! This could be the problem! I remember when I hooked mine up the wrong way once it idled rough on petrol!

Maybe swap the plugs on the O2's (only take you 30 seconds) and see if it resolves the issue!

 

[billabong]

Thanks guys... OK down the shed I go again with a torch.

 

[billabong]

Mello, I owe you a beer or 10 mate.

Yes, the 02 sensors were switched, it's going better than ever now and I got my smile back. Shortly I will upload a you tube video of how it sounds and goes now.

 

[MelloTB48]

know worries mate always here to help. It probally helps i did my apprenticeship and worked for Mr Nissan for 7 years

 

[gobush]

Hi mate i had extractors and exhaust done and mine did exactly the same thing just switched the o2 sensors and it run fine.

 

[billabong]

know worries mate always here to help. It probally helps i did my apprenticeship and worked for Mr Nissan for 7 years

Just glad I didn't listen to the two mechanics that told me to replace the coils. I am still lost as to why it seemed to drive fine for the first few days after fitting them, but that doesn't really matter now anyway.

 

[OILRIG]

just to add something to this. both my o2 sensors didn't work and didn't throw a code,also driving with them disconnected didn't throw a code.so don't rely on the check engine light 100%