It's getting spark and plugs look as good as plugs can look. I had a cyl 3 misfire like 5 months ago and that was the same time the running hot started after I did an oil change and air filter... The misfire I came to thinking was clogged fuel injector so started putting Lucas fuel system cleaner in the gas and after that the check engine light was gone till now......... The head on the passenger side is 2 years old so is the radiator. I can't remember exact numbers but I did compression check on a few cylinders and the ones I checked with the new head where around 125-130psi and cyl 3 was at like 98 or around that, these measurements I took around 5 months ago when I first was having the misfire...

I am soooo confused......


Forgot to add there's 142k miles on it

 

I hate to think that those two things are related but seeing as you have had this problem before I am inclined to think they are. I would like to think the misfire is the injector which you could swap to another cylinder to check. I know someone is going to say this so I will beat them to it...That is work to just rule out an injector. Question, since it has started running hot again has it actually overheated? I mean to the point you had to shut it down, temp into the red, steam, etc. Also, have you had to add any coolant?

Other than that I'm still scratching my head. Overheat could still be the water pump. I know you still have heat but maybe it's not moving enough fluid to keep it cool. Does it run warm all the time or just around town at low speeds or does it do it at highway speeds as well?

 

Cylinder 3 is on the drivers side, second one back from the front. 98 pounds is low..... wonder if ya got a crack on the valve seat on number 3.......

 

How in the world did I miss that. lol Long day at the shop today. It's 8:30 and I'm still here buttoning up a car we have had for almost a week. It's beer time. Who wants one?

 

I'll take one. Pass 'em around.

 

I can tell that it's beer time when I start over thinking things. I blame this 94 Olds that I have been re-wiring all day. lol

 

The overheating has been going on forever but when it's cooler outside it seems fine just now that it's getting hotter I'm having to turn heat on to keep it around 210 the hottest I've seen it get is what I'm guessing about 235-240 it hasn't got into the red zone it got about half way on the gauge from the 210 mark to the beginning of the red mark.

Wanted to add it has a 21psi rad cap from what I've read that will put the point to where it actually bursts at something like 275f but I also read over 240 is the scary point for aluminum heads O_O

Oh ya also it doesn't smoke at all and coolant is clean and green and it doesn't overheat when it's sitting at idle infact after it starts getting real hot if I park and let it sit there eventually the temp will go down to normal

 

Radiator cap is only supposed to be 16PSI, any particular reason for the uber cap?

 

^^^My question too. 21psi is high and if you have a weak point in the system...

 

Actually the dodge dealership put that cap on there when they replaced the radiator I've always found it weird aswell... As for the psi of the cylinder I had a theory, let's say the gauge I used was broke and giving inaccurate measurements so let's say they pressure was fine couldn't the high temp cause preignition in turn causing a misfire?