Okay all. I have been on here trying to find what might be wrong with my 97 4runner. I have the 3.4L V6.

Seems my problem is my #5 cylinder is missfireing. Now the problem is that it is only misfiring when the engine is cold. When I start the engine it is SUPPER rough running but as soon as I put it in drive everything works fine.

Now for some background. I just bout the car from a dealer about 2 months ago. I had the 4runner for about 2 weeks when it redlined the temp gauge. So I filled up the radiator and the reservoir. Seems that I blew the heater core with the over heating. So i just replaced the heater core and the hoses that attached the reservoir.

I tested the radiator with the liquid test to see if there was exhaust in the coolant. The test came back negative. Now it could be wrong but i don't know. Also there isn't any sort of indication there is water in the oil.

I am still having to fill the reservoir up about every 50 miles. I have no clue what is going on. any help would really help

 

My guess would be the rotted coolant lines going back to the rear heater. I just disconnected my entirely. The rear heater lines start up at the firewall where they branch off the heater lines and go straight down and back along the passenger side frame rail. They are probably slow leaking when under pressure. New lines will cost you $80 in parts.

#5 misfire might be a fuel injector. Have you pulled the codes yet?

 

I pulled the code P0305. Which is Misfire of the #5 cylinder.



I hadn't even thought about the rear heater core lines being bad. I guess I'll get under and check.