Misfire cylinder 3?????

[jirdesteva]

Hi, from NJ. I have been having a misfire issue at speeds above 55mph have swapped out plugs, wires, & coil. My cc's a 2003 s -10 with K & N intake kit. no other mods great truck bad mpg. Any info greatly appreciated.

[F9K9]

Welcome to the forum! What exactly is your "P" code that makes you think that you are having a number 3 cylinder misfire. What did your old plug look like? what plugs are you using? How does your distributor cap look like? Rotor?

[HenryJ]

I'll add to the list:
What plugs did you use? Is the distributor housing cracked at the cap hold down screws? When was the last time you added injector cleaner? When was the last time you cleaned the carbon from the throttle body? Have you replaced the "sub-standard" (IMO) stock plug wires?

[jirdesteva]

To answer the questions, Excel rotor, coil and cap no cracks, plugs used split fire, E3, and Delco. Wires used Auto lite, excel, and now taylor. Exact code can't recall the only thing leaking is the intake gasget at the front of the engine and that's more seapage than leak of coolant. At idle in drive or at any speed lower than 55 she runs smooth. When she gets past 55 on the highway the SES light kicks on blinks and after she goes under 55 the light goes out. I will get the exact code next chance I get. The plugs that I've taken out apear normal no crud or gunk no gap issues either. I use injecter cleaner every 6th tank full and only use mid grade gas. Changed fuel filter twice in the last year just in case.

[HenryJ]

Buy a set of Autolite Iridium spark plugs.
I tried running some exotic plugs and ran into a midrange surge. Just a few rpm , but noticeable.
The stock plugs are pretty good, but expensive. The design and materials used for the Autolite XP plugs are superior. There is a very good thread on the subject and my test results.

Change those leaking intake gaskets NOW! The gaskets can not only leak externally, but also internally. Burning coolant could easily cause a misfire. Get the good set of gaskets made by Felpro. Go green if you have not already.

Check your fuel pressure and do the tests for the injectors, pump, check valve and regulator. The fuel pump test thread will have the details.

[smilindave]

I had a misfire in cylinder 4 when I first bought my truck used in 2008. I first tried plugs, wires, cap and rotor button with no luck. Seems like I remember that the SES light would also blink at certian RPMs. It turned out to be a broken valve spring. I had the truck to three different mechanics before anyone found the problem. I had the valve springs replaced and that fixed it. That was 30,000 miles ago and I have had no more problems with it. Please let us know what the problem is if you get it fixed. Good luck.

[killian96ss]

Knowing what code is stored would help alot! Misfires can be caused by many things.

Steve

[RebelKid1822]

i also have have the cyl num 3 misfire code apear, along with random miss fire codes. my truck does it when around the same speed every once in a while, however i dont notice a power loss. it dose it more when the engine is under a load like towing, which when towing it seems sluggish. i am woundering if it is the spider injection system? i have changed the plugs twice, wires cap and rotor. had a leaking intake, relaced it, truck still dose it. all other maintenace is up to date. any ideas?

[roadrunner]

Check for air leaks into the manifolds or exhaust. My air injection manifolds leaked and caused both the codes you are talking about. I also had a cracked Y pipe at it's junction cause these codes as well.

[RebelKid1822]

ive replaced my intake gasket not to long ago, i dont see any black around my exhaust manifolds so i dont think there is any air getting in there, i alos found no cracks in my exhaust pipe..

[roadrunner]

It has been my experience when you get any individual cylinder miss-fire codes along with random miss-fire codes at the same time there is usually something causing the fuel system to operate erratically with swings to and from both too rich and too lean. Other than exhaust leaks there can be many causes including faulty O2 sensors but usually they will tend to set their own codes. Absent that have you changed your fuel filter lately? Check the fuel pressure as well if the filter is okay. There is a sticky on the index on how to test pressure and what it should be here on the forum. Good write-up with pictures. Read and heed. Perhaps time for a good fuel system cleaner? Many here like Sea Foam. There are others out there as well.

[RebelKid1822]

i will try the sea foam, i put a new fuel filter on about 30k ago, i do injector cleaner every 3k, and buy a full fuel system cleaner everytime the code stays on the dash for a day. i have replace the bank 2 o2 sensor b4. thanks.

[HenryJ]

i put a new fuel filter on about 30k ago...

It is due for replacement then as 30k miles is the maximum service interval.
Do the fuel system tests.

[RebelKid1822]

ok thanks.

[RebelKid1822]

bought a fuel filter today, after i put it in i will do the fuel tests.

[RebelKid1822]

while putting the new fuel filter today, i had the truck in the air, found my y pipe is cracked! right along the weld....dnt kno if i should try and weld it or just get a new one

[roadrunner]

That would certainly have a bearing on your codes. I welded mine and added a strap of metal down one side of the RH down-pipe around the cross-over and back up the other side of the down-pipe. Welded all in place and have had no further trouble in that area.

[RebelKid1822]

mine is cracked right along the weld on the top and drivers side of the y pipe junction, i will drill and weld it tomoro, hopefully thatll do it. the crack is not gapped apart at all, which is y it was very hard to see.

[RebelKid1822]

just finished welding the y pipe, was a pain to get to. gona drive it a while and see if the code stops appearing.

[RebelKid1822]

just replaced mass air flow sensor, had light flahing still, was told to replace it. i was told that it can also cause the codes i have been having along with the symtoms, i was also told this may help my mgs which have been going down over the last year, ill let ya kno what i find after i drive it for a few days.

[HenryJ]

The MAFS failures are pretty rare in my experience. They can get dirty and fouled, but cleaning them with aerosol MAFS cleaner, or careful swabbing with a Q-tip and rubbing alcohol usually restores proper readings.

Clear your codes and reset the operating parameters by removing both battery cables for three minutes after you make any change or perform service work. This will set a new cold start sequence and refresh the cold run information.

[RebelKid1822]

the one i removed was perfectly clean- looked just like the new one. ive ahd the batteries unhooked alot lately messing with the 4x4. ive had those codes coming up for a long time, the trucks performance had just steadily been getting worse when i put a demand on it. just regular driving and idling fine, towing and highway caused the codes to appear. the harness was corectly plugged and snapped onto the conector, wires appeared undamaged. now i just gotta play the waiting game. see how the truck acts over the next few days.

[ApproachMedium]

wow hilarious. Someone that lives in NJ and has the same truck with the same problem I do except its the exact opposite. Mine idles like crap and wont fire #3, runs great on anything over idle. Drive it around town MPG sucks, drive it on highway 19mpg...

My problem was rooted down to a loss of compression on cylinder #3 and #4. Might not be a bad idea to check the compression if you have a high mileage engine. I have had this problem since I got the truck with 190k on it and im at 246k now, so its not like it will die tomorrow. Esp. if you keep changing the oil with Lucasoil like I do.

[RebelKid1822]

ever since i replaced my mass air flow sensor, i have been getting almost 20 mpg, its been 19.4, 19.6, etc. this is way better then what i was getting. it was around 15, 16mpg if i was lucky. the ses light has not come on at all for a few days. truck runs great. hopefully this will be the end of this poblem for a while.

[roadrunner]

That would definitely explain the mixture swings and described codes you were having. Glad it's working for you now. BTW you are now in the highway mileage range mine gets too so your system must be working pretty well now.

[RebelKid1822]

awsome thanks