# TBelt/Alt/Radiator/plugs/wires/icoil... wth is next... p0300 misfire =(



## Jeffus13 (Apr 12, 2009)

My last 6-8 weeks... I need some help if possible...

1)valv cover/tensioner gaskets

car started misfiring after this... figured i aggrevated an old wire but was nervous about it being the coil... not too horribly expensive to replace... so replaced all

2)changed plugs(NGK iridium)/wires(Bosch)/ignition coil

drove 1000 miles to NC and back... no problems... next day... 

3) alternator bad... replaced alternator adn while it was open i replaced timing belt/thermostat/roller/idler/dampener/water pump and cam seals (80k on car... about time anyway)

seems to be ok... runs for a couple days so i take i to be state inspected... it fails due to a wiggly control arm but thats beside the point... seems in the last 2-3 days it has a new problem..

rough idle at startup in the morning... once i throw it in gear everything is fine. This morning i let it run longer than i usually do to see if it would smooth out... instead it throws the p0300 multi misfire code along with some individual misfire codes. 

i read on some other threads that possible temp sensor? Vac leak? Any other ideas? It doesnt give me any problems the rest of the day.

only off the wall thing i can think of is when i was doing the valve cover gaskets i lost a nut... i used the nut off the sensor that is attached to teh front of the ignition coil and replaced that one a couple days later with an aftermarket that has a plastic insert... is this nut important for the sensor to ground that could be causing me any issues? Seems to have worked fine on my trek to NC for 1000 miles... not sure exactly what the little sensor is... its a little square about an inch in size that goes on the bolt there. 

Edit: found this picture of the sensor im talking about... not my picture... bottom center of screen... right-front end of ig coil. 

http://farm5.static.flickr.com/4012/4461256066_68539235b2_b.jpg


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## O_o (Nov 12, 2009)

Not much to add, I'm afraid.

It sounds like it _might_ be the coolant temperature sensor. Usually if the CTS is fubar though, it will be hard to start as well, but for $15 and as many minutes, you might as well replace it if you suspect it.

The fact that it's only first thing in the morning isn't really consistent with a leak in the vacuum lines or intake, but I'd look for one anyway. How long does it run rough? If its only a minute or two, I'd take a look at the SAI, if you have such a thing.


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## Jeffus13 (Apr 12, 2009)

THanks mate... 

I looked back and realized that my temp sensor was replaced a year or so ago... but i still didnt realize it until after i had already bought a new one from dealer (around $40 for sensor/ring/clip)

I also had a new symptom start... the car was shutting off on me anytime i slowed down too much... if i was running 45 and braked for an oncomming light it would die on me when i got down to around 15mph or so. If it was under load (A/C) it was even worse.

anyway... 

I dug around and found a vaccum line i had missed when i did the pcv system last year... so i replaced that... then cleaned the MAF with CRC MAF cleaner and the car runs like a champ! No problems so far in 2-3 days of constant driving. Appears to be a dirty MAF as culprit. 

I will be cleaning my MAF with each filter change from now on for sure.


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## Slimjimmn (Apr 8, 2006)

that nut is for the ignition suppressor. You should have that grounded (bolted up) as it helps prevent radio static and such.


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