scorchpa

So I spent the last 4-5 hours wrestling with removing and replacing the coolant tank. Got it all back together and went to flush the coolant (drained old coolant, filled with water and flush fluid). Was running the engine at idle, and everything was going fine but then as temp started coming up after 5 minutes or so to about 100-110, the engine started running rough, followed by check engine light and the following codes...

P0300 - Random/Multiple Cylinder Misfire Detected
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected

What should be some of the first things I should check?

Thanks in advance

extanker

you may have got something wet...coil etc. let it dry out ?check your vacuum lines ,may have disconnected due to the work done.i hope you did not overheat and pop a head gasket

Imo000

You really have to over heat and idling engine to warp the head and blow the gasket. Since there is no load on the engine, it heats up evenly, even during over heating and nothing warps. Chances are the # 1 &#2 coils got wet. Since they are probably cracked from age, the water/coolant shorted it out. Let it dry up anf see if the mussfire goes away. However, this is a sign that the coils are due for a change.

CDLVancouver

funny (not haha but hmmm) i did the exact same as the OP.
finally got er all hooked up yesterday and she ran really rough. it didnt pull out any codes yet but the check engine light did flash. thought maybe i did something when i dropped the engine. so on monday will check codees and thinking its the coils, or else a vaccuum line...could the maf sensor affect this as well?

scorchpa

So... after letting the car sit for 4-5 hours, I cleared the codes and started it up.... once again, everything was smooth (just idling in the garage), until the temperature reached about 120F after maybe 5 minutes, and then started to run rough with a misfire on cylinder #1.

doesn't sound like coils being wet.... would that be a symptom of loose vacuum line? I'm actually not sure where to check for this... I'll be searching google in the morning, but if anyone can point me in the right direction I would appreciate it.

FYI - 2002 C4 Cab.

Ahsai

Have you disconnected the evap line that goes into the evap purge valve? Any air in the cooling system? Vacuum refill tool or manual bleeding?

scorchpa

Bingo.... Air in the cooling system.

CDLVancouver

Weird...air in the cooling produces misfire codes?

Ahsai

Possible the air pockets affect the temperature pickup of the coolant temp sensor, which then throws off the fuel trims.

scorchpa

I haven't had a chance to run the car for an extended period since, but I opened up the bleed valve again once idling, and saw color of "flush" coolant change... In other words I wasn't circulating the fluid... Probably causing water pump to cavitate.

Ahsai

Makes sense. You should definitely perform the manual bleeding procedures that involves cycles of revving the engine to higher rpm once warmed.

scorchpa

Well.... Got out there again and more misfires on cylinder 1. Ran smooth for about 10-12 minutes... Temp got up to 160 then misfire... I'll let everything dry out and try again in the morning....

On pelican website it says to rev to 5000 rp during flush, but in park, only can get up to 4000.... Seems to be limited there... As that because I have a tip?

Ahsai

Yes, most likely limited by the tip. However, 4k should be plenty anyway. Maybe trace back what you disconnected and make sure all connectors, hoses are seated correctly and no air leak? If #1 misfire persists, you may want to remove the coil and plug to inspect them carefully. If multiple misfires, I would suspect wrong fuel/air mixture because any wetness on cracked coil should have dried up by now.

You connected back the evap purge line, right?

scorchpa

Not sure I disconnected it?? Sorry, kind of a newb at this. Do you have a picture of what it looks like and I can check whether It's connected securely or not?

scorchpa

another quick question..... if I was running the engine for 5-6 minutes without the water running through the engine, could it have caused any catastrophic damage which is why I'm still seeing check engine light? Though after I got the air pockets out, I was running for 10 minutes or so until it started to run rough again.