View Full Version : Misfiring at startup

09-22-2008, 05:34 PM
I've noticed as of late when I start the 'maro when it's cold, it misfires a little. When it misfires, it makes a sound that's like that spurt of air you get when taking the hose off an air tool, just not nearly as loud.

Any ideas?

09-22-2008, 05:39 PM
I would imagine its throwing no code correct? Is this the only time it does it?

09-22-2008, 05:47 PM
Yes, no codes and only when I first start it after it has sat for a while.

09-22-2008, 05:59 PM
leaking injector maybe if it is when it sits for awhile. Maybe leaks a bit and then when you do go to start it there is some fuel there

09-22-2008, 06:58 PM
when is the last time plugs/wires were changed on the car? Without any type of scanning tool (like the ls1m) its hard to track down a misfire. I would start with the cheapest first, being the plugs. Do you know what gap you have them at currently?

09-22-2008, 07:53 PM
All that stuff was changed probably 20-25K miles ago.

09-22-2008, 08:48 PM
Like i said earlier its really hard to pin point a misfire without a scanner. For your situation i would start cheap and change the plugs and wires ( even if you dont want to change them, at least pull them to inspect the wires, boots, and read the plugs). you can tell a lot from the tip of a plug (which might tell you which cylinder is misfiring). you can find a chart in a chiltons manual or on the net to desicribe why the tip of a plug looks like it does (running rich, misfires, etc). While your under their it might be a good idea to check vac. connections as a vac leak can cause a rough idle. (seeming like a mis)

09-22-2008, 09:06 PM
It only does it when it's cold and idling... never when I hit the gas. I'll just say it's cammed.

09-22-2008, 09:08 PM
So it sounds like its slightly camming? that is definetly pointing to a vac leak. very common when this happens

09-22-2008, 11:34 PM
Hmm vac leak, huh? I'm a vac noob. Any pointers?

09-23-2008, 12:08 AM
yea take some carb cleaner and spray it round vac. conections and vac lines in gerneral. if you hear the engine rev or sputter a little your prolly looking at your vac leak.