landlords2

Im getting a multi random cylinder miss fires. I have used GM top engine cleaner changed plugs and wires. Have no clue where to go from here. the miss seems to get worse with the warmer the car gets warm. I have also had the injectors cleaned. Please tell me where to go from here.

WicketMike

iTrader: (13)

do you have a large cam? or is it stock?

landlords2

Im sorry my fault its a 01 stock T/A with Mac Headers, No cats and borla exhaust, and a Predator programmer with 60k

ss rally red

iTrader: (8)

A vacuum leak can also cause a random misfire.

jpz28

How would you check for a vacuum leak...and where does usually happen?...

ss rally red

iTrader: (8)

I agree that there are few places for vacuum leaks on a LS1 just check around the intake manifold or possible around an injector, or EGR system. Just trying to help.

M.Roberts

iTrader: (4)

I have the same problem in my siverado. It started right after cam install. Maybe I disturbed a seal or hose and caused a vacuum leak.
The cam I put in was small enough that it was not supposed to upset idle to the extent that it has.

eallanboggs

iTrader: (1)

I get the P0300 on my Silverado too after I did a cam install, but it resets itself pretty quickly. The first time the SES came on I cleared the code with AutoTap, but the MIL still comes back on. Before I can reset it the PCM clears the code on its' own. I only get the code after a cold start when the engine hiccups while trying to warm up. My LSA is 112 so that may be why I sometimes get the P0300 DTC. As far as the vacuum leak you should use a gauge to check for erratic reading. It will be apparent if that is the cause by the gauge reading. Locating the leak will be the hard part. Go back over any work you have recently done and check all hoses and their connection points.

stage274

I fought that code..... Turned out, it was a bad battery... Yep... Get the battery tested first, then chase it down.

lq4headache

Hey guys I just came across post and I'm dealing with this proplem right now ...

I have a lq4 6.0 with a set of ported 317 heads with the comp cam 54-459-11 camshaft. With a set forged wisco pro piston the motor is killer I just finished all the ecm tuneing today but up till this point I have been getting po300 code at idle in drive my tuner says he thinks it's the camshaft but after seeing on here it could be a battery? ?? Has anyone ever come across this with this cam input needed

2xLS1

iTrader: (25)

So you don't think the lope produced by a 231/239 113 LSA is going to upset the misfire detection? If your tuner doesn't understand this (he thinks it's the camshaft) or what to do about it in the tune to prevent it you should probably be looking for a different tuner.

lq4headache

Ya I hear ya like I said the final tuneing was done today so we will see . Well I was having this po300 come up the ecm was only on a bench tune all the data logging was done and finished today .....So for I am new this ecm tuning this can be fix by tuneing the guy who did the tuneing is mgs performance he has been around for 20 plus years let hope he knows what he's doing

lq4headache

Is there any guys on here from the toronto canada area that that know of a top tuner in case I end up needing one .....