Misfire Cycl 2 Tried about everything...

**Camaro98Z/28** · 03-30-2009, 02:06 PM

Had my car for the past week at Chevy to figure out why I was getting a random misfire.
I cleaned the MAF, EGR, had new ac delco plat plugs and wires installed, as a new fuel filter.

While at Chevy they claimed that it was the O2 sensors causing the misfire, they replaced them, it cleared it up a bit and isolated the misfire to cycl 2.

They have installed a new plug, wire, coil and injector.

They are getting great spark, plenty of fuel pulse and everything pretty much checks out.

They are now telling me it has to be an internal issue...

Since i bought the car, it has had a noisey lifter on the pass side in the cycl 2/ cycl 4 area...

My question, could the lifter be my problem with the misfire on cycl 2?!??!

Thanks alot guys!

**rbob93** · 03-30-2009, 03:31 PM

Check this thread out

http://www.ls1.com/forums/showthread.php?t=110204

**Camaro98Z/28** · 03-30-2009, 03:46 PM

read it
didnt see how it can helps though
i dont have bent rods or bad rockers, dealer checked it
did i miss something?

**Camaro98Z/28** · 03-31-2009, 12:00 PM

Nobody....

**Cutlass** · 03-31-2009, 12:24 PM

A leak down and a compression test should isolate almost any internal issues. Otherwise you could take off that valve cover and look at the 2 #2 rockers while the engine runs and see if they are moving as much as the other ones. If not then maybe a worn cam lobe, bent pushrod, or broken valve spring.

**jmatt07** · 03-31-2009, 05:28 PM

did they put the coil pack harness on backwards? sounds crazy but that happened to me after i did h/c/i swap. the car ran but sounded like it had a mis. come to find out i put coil pack harness on backwards and it made the computer fire the wrong cylinder at wrong time.

**Wesman** · 03-31-2009, 07:41 PM

Originally Posted by Camaro98Z/28

Had my car for the past week at Chevy to figure out why I was getting a random misfire.
I cleaned the MAF, EGR, had new ac delco plat plugs and wires installed, as a new fuel filter.

While at Chevy they claimed that it was the O2 sensors causing the misfire, they replaced them, it cleared it up a bit and isolated the misfire to cycl 2.

They have installed a new plug, wire, coil and injector.

They are getting great spark, plenty of fuel pulse and everything pretty much checks out.

They are now telling me it has to be an internal issue...

Since i bought the car, it has had a noisey lifter on the pass side in the cycl 2/ cycl 4 area...

My question, could the lifter be my problem with the misfire on cycl 2?!??!

Thanks alot guys!

Sounds like your dealership employs parts changers, not technicians.

There are tests to make sure wires, coils, and injectors are functioning properly without replacing them.

If the problem has been isolated to cylinder 2, and its been determined that its has good spark and fuel, its time to start looking at engine internals. Failed lifter, bent pushrods, burned valves, cracked head, ect. They need to actually diagnose the issue instead of just guessing what might be wrong.

**Cutlass** · 04-01-2009, 05:34 AM

^^^agreed

**Cutlass** · 04-01-2009, 05:36 AM

Hooking up a vacuum gauge is another test. If the gauge needle fluctuates rapidly, that indicates a valve train problem.

**Vexzer** · 04-01-2009, 12:27 PM

"random" = "intermittent"?
Exactly how did they isolate the "random" misfire to cylinder 2?

**Camaro98Z/28** · 04-01-2009, 05:39 PM

it was a random misfire
replacing the O2s isolated it to cycl 2
im tearing off the valve cover tomorrow and am praying for a broken valve spring or a failed rocker...
we shall see though

**BMJ99Z28** · 04-01-2009, 05:52 PM

I've heard of the rocker arm bolts backing out on these engines before if you're gonna have the valve cover off check that too.

**Blue_01_Z28** · 04-02-2009, 09:35 PM

I have the same problem with my car. I did the compression test on that #2 cylinder and it gave me about 15PSI, NOT GOOD! It has a misfire, but I haven't taken it apart to see where the problem coming from.

**Camaro98Z/28** · 04-04-2009, 08:02 AM

problem solved
thanks guys
turned out to be a broken valve spring...

**rbob93** · 04-04-2009, 08:31 AM

Let me get this straight.....The dealer checked for bent pushrods & bad rockers but couldn't see a broken valve spring???

I think you got ripped

**Cutlass** · 04-04-2009, 12:30 PM

They must not have down that compression test or a cylinder leakdown test because a broken valve spring would show up (ie the valve not sealing). Sounds like the head tech at Century Chevy is a ignorant cheat.

**Wesman** · 04-06-2009, 11:41 AM

Originally Posted by Cutlass

They must not have down that compression test or a cylinder leakdown test because a broken valve spring would show up (ie the valve not sealing). Sounds like the head tech at Century Chevy is a ignorant cheat.

I'd agree.

Its not one of those one in a million mystery problems that requires bringing in a company engineer to figure out. Its a broken valve spring, pulling the valve cover should have been one of the first things they did once they deducted that it wasn't an ignition or fuel related misfire.

I also love how changing the O2 sensor somehow helped them figure out it was a broken valve spring.

Seems too many people these days should be working at McDonalds, not as technicians at a dealer.

**mark21742** · 04-06-2009, 05:13 PM

Originally Posted by Wesman

I'd agree.

Its not one of those one in a million mystery problems that requires bringing in a company engineer to figure out. Its a broken valve spring, pulling the valve cover should have been one of the first things they did once they deducted that it wasn't an ignition or fuel related misfire.

I also love how changing the O2 sensor somehow helped them figure out it was a broken valve spring.

Seems too many people these days should be working at McDonalds, not as technicians at a dealer.

it is amazing how it seems like you'd have better luck letting a monkey with a hammer work on your car than a "tech" at a dealership....i have a few friends that are very good mechanics/ techs that i would and have called for advice, but other than a slight few i have no faith in the dealership personel

**02blackz** · 04-07-2009, 04:29 PM

im goin thru the same prob!!??, i went to autozone to have it scanned and P0300 popped up. i already changed my plugs-ngk tr55, and wires-msd sc8.5, but still no change. i need to try to do the pressure test or open up my v-covers to see whats going on in there cuz its hurtin pretty bad.

BTW-i went to a cousin of mine (a chev. hater) and said it was becuz i put the perf. wires and plugs. i honestly dont think so bit he did make me doubt what im thinking (internal problem). he made me switch ign. coil #1 w/ #3 and the problem persisted. but ignorantly that was his explanation and wanted me to buy stock acdelco wires n plat plugs. this forum is helping me more than you guys think so any more comments comming here could help someone else, thx!!!