Ls1 misfire

[Craigf18]

Hey guys ! I have a Vz ss 5.7l , I’ve recently replaced the coil packs lead spark plugs & the knock sensors & the car is running rough , misfiring & really unresponsive & feels like it wants too stall under low rpm , even when it gets up in the rpm range it still Is carrying on like it doesn’t want too be driven , I noticed the issue a while ago when I first brought the car & it would randomly start shaking & dropping the revs sitting at sets of lights , it throws a SVS code on the dash but when hooked up too a computer doesn’t show any fault codes , the battery was recently replaced but I don’t think that would make a difference , not very mechanically minded so any advise would be appreciated ! Thank you.

 

[BlackVXGTS]

You need to find a scan tool (Tech2 or equivalent) that displays history codes. Most cheap scan tools only show current codes which doesn't help with intermittent problems.

 

[Craigf18]

You need to find a scan tool (Tech2 or equivalent) that displays history codes. Most cheap scan tools only show current codes which doesn't help with intermittent problems.

I’ve had it hooked up too a snap on computer ? Still didn’t throw any codes on that

 

[lout]

if service vehicle soon comes up there should be a code
unless it is the ecu/power to ecu causing the problem

 

[Fu Manchu]

Blocked exhaust?
Poor fuelling. Have a look at fuel trims.
Vacuum leaks. Smoke test the intake.

 

[LockyDub]

Just had the exact same problem fixed on my LS1 Stato. Car ran rough on start up, shook violently and stalled out at lights, had a delayed throttle when cold and threw check engine codes daily.

Codes were showing for fuel bank lean and turned out I had faulty O2 sensors and damaged leads which got replaced. Had the air filter and maf sensor cleaned out and car runs like new now. I’d say your O2 sensors might need replacing too, once they’re cooked they throw everything out of whack.

 

[Fu Manchu]

But first they should be checked and their data verified before changing them. A having a dirty MAF (not the first time for some of you) will lead to poor fuelling data. So the sensors may seem to be at fault but the real cause is upstream. Let’s not load up the parts cannon and give shares in Repco a bit of a lift. Do it methodically.