NASTY1

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??

zamora7

iTrader: (4)

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.

NASTY1

the plugs should be good. not sure bout the wires and coils. whats the best way to figure out which ones arent firing? who makes wires for relocated coils, i still have a/c and factory brake booster.

zamora7

iTrader: (4)

For the wires right now is the best time to check. Start your car in the dark and look under the hood and look out for sparks coming out of the wires.

As for the coil packs, which cylinder is the misfire coming from?

NASTY1

All I get from the scanner is random misfire. I don't know which cylinders. It idles bad. Ill pull the wires tommorow.

99LS6SS

iTrader: (4)

What are you scanning with?

67firebirdak

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.

NASTY1

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!!!

NASTY1

also whn i unplug maf it idles up and seems to run better. but then i get the maf code. i was told running in limp mode was bad for the tranny.

-Q-

iTrader: (10)

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.

NASTY1

my valve covers have breathers in them and since the egr valve and emmissions are programed out i just put a plug on the pipe at the throttle body. could having the line plugged be causing it.

ReApEr75

iTrader: (4)

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

NASTY1

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.

99LS6SS

iTrader: (4)

log for misfire. see if someone makes a misfire.cfg. also when I had a plug wire fall off i could hear it sparking across from the wire to the coil. it was pretty loud

-Q-

iTrader: (10)

I have a misfire.cfg for HPTuners if you need it...I can't seem to get it to upload though. Shoot me an email address if you want it.

NASTY1

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?

ls1nova71

iTrader: (4)

That little vacuum line originally went to the HVAC, you should plug it.

NASTY1

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 $$$$$

zamora7

iTrader: (4)

Fuel pump issue? Fuel filter?

-Q-

iTrader: (10)

It sounds like there is a vacuum leak coming from somewhere. They can be a real bear to track down.