Misfire Cyclinder 4

[MasterP]

I have check engine code about misfire in cylinder 4, i have changed spark plugs and ignition wires, after that i reset ECU and was not getting code again, however engine vibrates on idle randomly and cannot hold steady idle RPM, i assumed it was a idle valve issue.

Was driving on freeway for a while at 70 miles per hour however misfire code did not come on, but after taking car to smog shop i had it back, why is that?

I am considering cleaning injectors next, but i'd need to know which exact cylinder on the engine is number 4?

 

[boominXplorer]

I assume your working on a 6 cyl so it would be drivers side all the way in front. If your working on a v8 it's in the very back on the passenger side.

 

[Turdle]

A very common mistake made when replacing spark plugs and wires is geting the wires on the driver side (4-5-6) mixed up.

Triple check the firing order -- I highly suspect this is the issue.

Edit, maybe not. The best way to troubleshoot a random misfire IMO is to look at the spark plug, compare it to 5 and 6 on the same side.

If it looks real clean-it could be fouled by a coolant leak. Look very closely at the ceramic around the electrode for a hairline crack.
if it looks very white-fuel starvation (lean)
if it is black or dark brown, it is being fouled by oil, coolant or excessive fuel.

 

[Stick4503]

My experience with a number 4 misfire on these engines with an improvement with spark plug change that returns is a bad head gasket. Not totally blown out but leaking. Try a compression test.

 

[Tech By Trade]

Another option is with the wasted spark system 4 and the one directly across which I believe is 2, but I would have to look at the diagram to be sure, fire at the same times. You can try swapping the wires at the coil and see if it follows. If not its not the electrical system. Only works on the V6. Take a real close look at the IAC as well.

 

[MasterP]

It's 4L v6 with 121,000 miles.

Where do i find correct firing order diagram?

Engine is shaking on idle when i changed the plugs it was not so bad however after couple hundred miles it shakes worse and misfire comes on same day after being reset with scanner.

Spark plug in cylinder 4 was not champion other ones were original motorcraft so it must been ongoing issue with this engine.

I noticed spark plugs tips on driver side of engine were somewhat dry and orange and on passenger side of engine are wet black what does it signify?

Here is that plug up close

 

[XLTrunner]

While you're trouble-shooting, don't forget to check your coil pack...and, clean the rust off the metal contact plate on the bottom.

 

[Turdle]

Well, you need new spark plugs, I see no electrode nipple. I mean, holy gap batman!

You really should use the proper spark plugs also, as the coilpacks fire in pairs. From what I understand, one bank actually fires in reverse, so motorcraft, or autolite platinum plugs are the recommended choice.

The orange tan color is normal, the passenger bank plugs are just plain old and fouled.

Most good spark plugs come "pre gapped" but you should still check them with a feeler gauge, the proper gap is also very important.

 

[Tech By Trade]

I do believe its 3 and 4 that fire at the same time. One on exhaust which does nothing and one on Power. Should be able to swap the wires on the coil and see if it follows the wire or stays on the same cylinder.

 

[MasterP]

My experience with a number 4 misfire on these engines with an improvement with spark plug change that returns is a bad head gasket. Not totally blown out but leaking. Try a compression test.

you might be right i see oil in the radiator expansion tank and radiator itself and i smell crankcase gases in radiator. Would not think changing PCV would help much but i'll look at that.

If head gasket indeed leaking how would this cause a misfire in cylinder ?

 

[Stick4503]

Coolant can enter the cylinder and affect the air fuel ratios and combustion. Or compression is lost causing bad combustion.

 

[MasterP]

Okay ill check compression in cylinders and compression test on cooling system.

Another thing i got new PCV acdelco and its leaking little bit of air in opposite is this normal i thought it supposed to seal completely?

 

[gatzdon]

Quite a bit of good advice above to diagnose.

I just wanted to add two things:

1. Don't clear the codes. Don't clear the codes (yes I said it twice). Unless the code is disabling something on the engine and the manual says to clear it, you are putting yourself at a disadvantage by clearing the codes.

2. Get Forscan (or Forscan Lite) and a bluetooth OBD Scanner so you can read the codes from the PCM directly. Most programs (inlcuding anything at the autostore) are only reading the OBDII codes which are limited. With Forscan, you will not only see the codes from the PCM (and all other computer modules in the vehicle), you will also see the pending codes which will give you quicker insight on whether the misfire condition has gone away or when it returns.

It takes several drive cycles for many codes (including misfire) to set an OBD code. Additionally, the underlying PCM codes tend to be more prescriptive, especially when you can see multiple related codes (as opposed to one generic OBD code).

Good Luck.

 

[Grego50]

How much coolant have you been going through mysteriously.

 

[MasterP]

I am adding about half gallon (distilled water) per hour drive or so. Also i see oil in the coolant (water) i have suspicion its transmission fluid because now my transmission went from full level to low in about 1000 miles. I could change radiator its just $110 bucks for new aftermarket one.


Is there some test i can do to make sure radiator failed?

P.S. tranny fluid odd greenish/yelowish color.

P.P.S. Engine oil is at constant full level.

 

[1998Exp]

Besides the engine problems, mixing coolant into transmission fluid is a very bad idea. If you want to keep that vehicle, you should replace the radiator and, at the very least, flush the transmission fluid. Some will say that flushing is not enough, because internal seals are already affected, but it's probably not worth spending $$$ on rebuilding the transmission in an otherwise very iffy vehicle - especially if it's not misbehaving (yet).

 

[XLTrunner]

Yeah...coolant in the tranny is NOT good. At this point I think I'd be visiting my local U-Pull for a used radiator to save some coin since you don't know what the lasting effects are going to be on the tranny.

 

[gatzdon]

Is there some test i can do to make sure radiator failed?

You can use compressed air to pump the cooling system up to 15-20psig. Search youtube videos for examples.

Don't use an air compressor to pump it up unless you are confident you won't overpressurise the system. Water is incompressible, so a bicycle pump is good enough to pump it up.

 

[XLTrunner]

If you've got coolant in your tranny, there's no further testing that needs to be done. Your radiator is toast.

 

[akcarl]

I had the same issue with a rough and sporadic idle. Replaced the EGR valve and upper and lower intake gaskets. Do a smoke test and I'll bet your intake is leaking around that cylinder.