random misfire p0300????
Thread Starter
Teching In
Joined: Oct 2010
Posts: 18
Likes: 0
random misfire p0300???? 00 s10 with 99 ls1 camaro heart transplant. engine idles rough and seems lil weak. have a new maf, tps, iat, 02's, coolant temp sensor, plugs, computer and harness. think bout the only sensors not new are crank, cam, map and knock. any one had this prob??
Have you gone through your spark plugs, plug wires, coil packs? Make sure everything tightened properly and that your spark plug wires are not cracked, anf for peace of mind take the valve cover off wherever the missfire is coming from.
As for the coil packs, which cylinder is the misfire coming from?
Staging Lane
Joined: Sep 2009
Posts: 71
Likes: 0
From: Anchorage, Alaska
I had this same problem with my 5.3L. Couldn't figure it out until I went and pulled all the wires off. Turns out two of the wires pulled straight out of the ends, so I replaced them with new wires and have had no problems since.
Trending Topics
Thread Starter
Teching In
Joined: Oct 2010
Posts: 18
Likes: 0
my scanner is an innova 3120. I pulled the wires off. all of em looked ok. i then put them back on and pulled them off 1 at a time with the engine running. i expected a noticeable skip when fireing and nothing on the bad cylinder. i pulled them off but, could barely tell a difference i did all eight of em. with any single plug wire pulled you can barely tell a difference. pull two wires and she dies instantly. no burnt o2 wires but the prob gets worse when hot. o2s are new. i pulled air filter and covered half of the tube with card board engine ran better witch makes me think im lean. but not sure, help im dying here!!!
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Check for a vacuum leak if you haven't already. Common areas for it to leak are around all the PCV fittings...drvers side rear, passenger side rear, and passenger side front. One of those fittings may be cracked. Happens all the time. I chased down an issue with this previously, and was lost until Frost pointed me in the right direction.
Hope this helps.
Hope this helps.
My friend did a cam swap in his ls2. Once the cam was in we cranked the car w/ out the coil packs plugged in to get the valvtrain moving around just to hear if any problems. Once there were no problems we plugged the coil packs in and started it. Threw the same code p0300 misfire. But that was because of the coil pack being unplugged. Started it up again, scanned it and deleted. NO more code. Check your coil pack.. just my .02
Thread Starter
Teching In
Joined: Oct 2010
Posts: 18
Likes: 0
i know they are plugged in but not sure they are good. all seemed to act the same when i pulled the wires one at a time. is there a better way to check em? i found a tiny vacuum line on the back of the intake at the map sensor that is not hooked to anything. does it have to be hooked up? or can i plug it also the current performance harness has 3 big grounds at the back of the intake. i cant get to the back of the heads with out removing the intake so i grounded them together with a ground from there to the body and to the engine.
Thread Starter
Teching In
Joined: Oct 2010
Posts: 18
Likes: 0
New ngk plugs and wires with insulation down by the headers. Still getn p0300 code. Just pulled off intake and found a vacuum line at map sensor not hooked to anything. Map felt loose in hole, gna change it. What should I do about line? Plug it?
That little vacuum line originally went to the HVAC, you should plug it.
Thread Starter
Teching In
Joined: Oct 2010
Posts: 18
Likes: 0
ok, to get up to date ive pluged the vac line at the map sensor. put in a new map, new plugs and wires, checked for vac leaks with spray. engine runs much better with new map sensor. still idles a lil rough but is drivable. after about a half hour of runtime code came back. i took it to an old school chevy guy.he told me the engine was skipping because it was lean. asked how he knew and he said he could SMELL IT. ? by now i think hes as full of it as i am. he gets a squirt bottle full of gas and starts spraying into intake pipe. damn thing ran perfect.... smooth idle, revd much faster. it actually sounded like a stock motor for once.
What should i try now???? if i cant come up with something quick im gna take to an engine tuner in jacksonville fla. which is gna cost me some $$$$$
What should i try now???? if i cant come up with something quick im gna take to an engine tuner in jacksonville fla. which is gna cost me some $$$$$
Fuel pump issue? Fuel filter?
ok, to get up to date ive pluged the vac line at the map sensor. put in a new map, new plugs and wires, checked for vac leaks with spray. engine runs much better with new map sensor. still idles a lil rough but is drivable. after about a half hour of runtime code came back. i took it to an old school chevy guy.he told me the engine was skipping because it was lean. asked how he knew and he said he could SMELL IT. ? by now i think hes as full of it as i am. he gets a squirt bottle full of gas and starts spraying into intake pipe. damn thing ran perfect.... smooth idle, revd much faster. it actually sounded like a stock motor for once.
What should i try now???? if i cant come up with something quick im gna take to an engine tuner in jacksonville fla. which is gna cost me some $$$$$
What should i try now???? if i cant come up with something quick im gna take to an engine tuner in jacksonville fla. which is gna cost me some $$$$$