random multiple miss fire p0300

misfires are extremely hard to diagnose. if you have a pro style scanner look at your reading and see if anything is out of whack. also check for vacuum leaks, hoses off etc.

I am a ASE certified and have a fairly good scanner. Im just wondering if there may be a common problem with this model vehicle. Since it is a used motor its hard to find a starting point. I was leaning towards a fuel injection problem but I have not checked for vaccume leaks so I will start there. That's very helpfu. Thanks for the pointer and if theres any way you can get me the cylinder identification so I can double check my wires that would be great. I assumed it was just standard General Motors. With 2 4 6 on the front and 1 3 5 on the back.

I dont' think you get a misfire code with cwires crossed but hell you never know. here ya go

another pic with firing order

I have seen a P0300 caused by crossed wires but only if its 2 or more cylinders and the was they make cars now I doubt it would even start if that was the case. But I have been fooled before. This motor is such a simple designe there's not a lot to it and being that its a used motor that we know nothing about I want to be extra sure everything was installed perfect before I start pointing fingers at the used motor. This is exactly why I try to avoid installing used parts. But with todays economy you have to take whatever work you can get. I am going to put the smoke machine on it tomorrow and check for vaccume leakes. I will let you know.

if you have mode 6 on your machine run that and it might single it out prior to doing smoke test.

okay this is a good one. I just bought this 2005 equinox and the person had the wrong plugs in it, auto lite platinum so I bought ac delco plugs and new wires to change them. I broke the plug for cylinder #2 and we could not get it out so we pulled the head, and a 1700lbs torque snap on impact gun could not pull out the broken plug (with an easy out). We drilled the plug out and re tapped the hole for a healicoil (or how ever it is spelled). then we put everything back together and new head bolts and gaskets, the works not cutting corners on anything. and cylinder #2 has only 30lbs of compression and is misfires on an idle but runs perfect once you start to drive it. the check engine light would flash for a bit then stay solid then flash again. after about 60 miles of driving continuously the light when out and would only come on flashing for about 2 secs every 10 miles or so. I am so F'ing aggravated and confused. any help would be greatly appreciated! When I say "we" I mean me, my step dad who owns the garage and a friend with 20 years experience working on cars. I really do not want to pull that head again.

Did you do a wet test on the cylinder to check for bad rings?

u should have the head checked by a head shop.u have a crack or bad valve on #2 cyl. and need another head or repair that one if poss.

I did not do a wet test, what is a wet test? and I did not have the head checked because the vehicle ran fine before we tore it out and all the valves looked fine... I ordered a new head but I really hope I do not have to use it.

wet test is when u squirt oil in the cyl. to ck. the rings.u don't need a new one u need a one from the head shop rebuilt.take the valve cover off and ck. the rocker arms on #2 cyl..