I purchased an oem maf as well as Bosch upstream 02 sensors. I have not replaced the down stream. I will check for leaks before swapping them out. I assumed it was not the 02 sensors since I am seeing the problem before warm up. Is it safe to use carb spray to check for leaks.

 

its safe so long as there aren't any flames present. I puff on a vaporizer so I just hit my device and blow where directed. If somebody in the household uses 1, grab that for a few mins.


If you do a search, there is a thread, and even a video of a member using the combustible spray to detect leaks.


what are your coolant operating temps?

 

i use a 180 thermostat. she seems to be happy around 189 give or take a couple degrees. but...... i just got CEL p0300 and p0304. multiple and cyl 4 misfire. A little history on this old girl. I had issues with p0304 and coolant lost 2 years ago. evey shop I went to came to the conclusion it was a headgasket failure. i assumed a failed block since there are no coolant passages near cyl 4. at any rate i pulled her apart and did a full top end rebuild. not the most fun i have had in the middle of a winter but it was a learning experience. what i found was a failing spark plug wire at the coilpack for cyl 4 and a couple small external leaks of the cooling system (this truck moved with me from a very warm place in california to a very cold place in upstate ny). the gasket i pulled off looked new. cyl 4 wasn't steam cleaned with coolant but it was covered in grime from the bad spark. after she was all back together with new heads, nice wires and plugs, new radiator, hoses, water pump and fan she has been fine up until a week ago. it started as a failing o2 sensor and alternator. after swapping those out and now getting a cyl 4 misfire i am worried it might be bigger than i thought. i will check spark tonight when i get home. oh and i am seeing alot of pressure in the cooling system. thanks everyone for all the help! this is a much better community than my rx7 group.

 

it must have been a relief to see that #4 piston looking like that when you removed the cylinder head; big sigh of relief. Surely the block hasn't failed since then, coolant temps well under 200 and such. remove all of the spark plugs on that side and make comparison; hopefully #4 isn't steam cleaned this round either. Come back tonight with good news.


I also rebuilt the top end on mine over X-mas break out front of my apartment building. They don't even allow anyone to work on their cars so I had to do all of the work at night time after the staff cleared out. There were a couple of cold fronts where I was out there in 20-degrees; that's pretty cold for TX!

 

Ok an update. Finally got a chance to pull the number 4 plug. It looks fine to me. I did find a pretty nice coolant leak at the heater core return line. Oddly a day ago it ran like new. Today I got multiple misfire