Misfire @ Idle

**Flobeast385** · 06-25-2006, 09:00 AM

Ever since I installed my cam i noticed that it would misfire only at idle, scanned it and came up with a P0300 Multiple Misfire. Looking at the misfire graph all cylinders were misfiring at idle but while accel. there was not even 1 misfire. I am currently on stock tune and was wondering if the cam could be causing the misfire at idle or would i have another problem. I have changed plugs, wires, checked compression, fuel pressure and all are good. Any help appreciated.

**oneBADDz** · 06-25-2006, 10:45 AM

I've been reading up alot on cams lately, otherwise I wouldn't know what to tell you, lol. You aren't misfiring, until you get a tune you will get that code randomly. The cam writeup on ls1howto.com says not to worry about it, it just comes with putting a bigger cam in an LS1

**ITP** · 06-25-2006, 12:25 PM

The pcm mis-interpretates the lope caused by your cam as a misfire.

**Flobeast385** · 06-25-2006, 01:43 PM

I figured that it was the cam because it is just doing it at idle and a code did not set until the install. I am getting it tuned very soon and hopefully that will take care of it. I also talked to Bryan Herter at pcmforless.com and he said that an average to large size cam would do that to the LS1 especially with a 112LSA. Haveing that said what do you guys think about a mailorder tune from pcmforless. Bryan the programmer said he has the same cam in his vette and could deffinitly get some power out of mine. The reason i am thinking of mailorder from his is because there is nowhere close that does dyno tunes and i am going to go with more cubes in the near future.

**Flobeast385** · 06-25-2006, 01:45 PM

Thanks for the replies

**ITP** · 06-25-2006, 06:15 PM

There has to be someone in NC that can tune HPtuner. Check out your regional forums section on here.

**silverTA2002** · 06-25-2006, 06:44 PM

Happened to me too. Totally normal.

You can delete the code (not recommended in case of REAL misfire) or you can make the engine less sensitive to misfires at low rpm regions.

**Flobeast385** · 06-26-2006, 03:01 PM

How would you go about making the engine less sensitive to misfires? I just need the light to stay off until i get it inspected, do you think raising the idle would help out for right now?

**gillbot** · 06-30-2006, 07:24 AM

What software are you using to tune with?

You need to locate the misfire detection at idle table and adjust those values.

**jimmyblue** · 06-30-2006, 11:15 AM

Misfire detection is dummied out at higher RPM and MAP
and only really "live" at idle and low cruise. You can play
with the thresholds to just barely make it go away, if
you have time to spend. Otherwise you can just shoot
it for barking all night.

Not to say some of it couldn't be related to the basic
state of tune, but anything that increases crank jerk
(lighter rotating components, imbalances, cam) is
going to increase the ripple and probably outside the
stock "normal range".

At least one of the mods on HPTuners' 'board is NC
based.