obd11 causes misfire with cam?

I have posted this in the LT-1 section and done several searches on this: One of my codes Autozone pulled was a multiple cynlider misfire other was tps code--the man said he couldnt tell me what was misfiring exactly just a broad idea with his scanner--on a search thread someone said with a bigger cam, the obd11 will sometimes throw a misfire code--that guy had a larger cam than i do --my cam is 212/218 with 1.6 in the .520 range--will obd11 cause this code sometimes or is it something else going on? Thank you Dwayne

Dont think the cam would have anything to do with the TPS sensor...I do know it will mess with the CPS(cam position sensor) since it counts the pulses(4) the cam makes..

Cody

I have both a general misfire code and often have the CPS codes. I dont know what it is but something is messing with the computer. It doesnt effect OBDI and OBDI doesnt have all the misfiring codes that OBDII has.

My car has been running like crap though so I dont know what the exact problem is....

My cam is 226/230 .534/.544 by the way.

CPS is a crank position sensor on 96/97, and thats under the timing cover. You also have stuff in the Optispark which has similar function, the timing disk inside the Opti has 360 holes, light passes through, etc etc

A small cam like that should not cause any real issues at all, if everything was assembled ok, which I assume it was. You lined up the crank and cam gears correctly before assembly yes? This is not just an occasional problem I assume.

Dr Mudge thats probably why my car has been misfiring, I dont think the guy who installed my cam new exactly what he was doing.:mad:

I myself haven't noticed a misfire, (my first cam), and its on a 112 lsa so any little bumping i have assumed its just the 112 lsa-car runs fine going -,but at lights is where my idle goes, my tps code, but this po300 was a new one that kinda got me nervous--but i have since read that cams and the obd11 will sometimes make the computer think its misfiring and i need a reprogram--Thanks for your replies Dwayne

I think you might be talking about my post. I put in a 230/236 cam in my 96 and the SES light has been flashing at me. Someone posted that this is due to a misfire, false misfire actually. I haven't gotten the car scanned but it runs fine...well used to run fine till I tried to readjust the rockers, needless to say messed that up and the car doesn't idle well. This weekend I will readjust them again...I will get it right sooner or later. I am waiting on a group buy or something for LT-1 Edit or TunerCat to come out with a version for OBD-2. $550 is a lot of money so I'm hoping TunerCat comes out with a cheaper version. I am about to get Alex Peppers scan tool for OBD-2 as I've heard good things about it. I also have to be careful with things since I live in CA and smog is an issue...still need a hookup ;)

sherwinz28, it could have been your thread, i got it off doing a search, dont recall who it was--my light doesnt flash, it was constant, off now,pulled the battery cable to clean iac and throttle body, past saturday-Thanks Dwayne

Are your guys idles wierd too? Mine never steadies and is always jumping around.

I have a friend who had a 96 LT4 M6 Vette on which we did heads and an LT4-Hot cam. Yes a cam in an obd-2 car will cause misfires to be reported erroneously. This is because a cam will make the car idle rougher, which is wrongly interpreted by the pcm. Now, you have a smaller cam but your car is an A4, so therefore idles lower than an M6 when stopped in gear.

The solution - raise the idle via LT1-Edit or a professional tune. My buddy bumped his up to 900 and the problem disappeared.

I have also heard that obd-2 LT1-Edit, one can, or will soon be able to, change the parameters of the misfire test. Probably more useful for the guys who have big cams and don't want to idle at 1200 to avoid misfires being reported.

Joe

Thanks for the info--Bryan at pcmforless e-mailed me back and also said the po300 code(my code), was common in cammed cars-said he could delete that-------Thanks to everyone who responed--Dwayne

As for the CPS may be you have the cam whith the shorter pin

93-94 type so check it out.