I just recently acquired a very nice 2001 Mazda Tribute V6. It has 133k on it. It was not running when I got it. The PO said there were cylinder issues?
I spent some time on it and did get it running. It had a couple melted vacuum lines (near egr pipe). I have spent a couple days changing out a few parts trying to get it running smooth. It did for a short time seem to run right, but when I shut it off and restarted it went back to rough. Sort of a miss.
I have replaced the plugs, intake gaskets upper and lower, several of the boots and one coil. I also replaced the TPS, IAC, pcv valve and EGR vacuum solenoid. Didn't want to throw parts at it, but napa had em and I tried em.
I had scanned it before anything and got no codes. I checked the codes on the odometer and some are unknown and others are low voltage and high voltage...
I will get those codes for anyone who can decipher the others.
I keep thinking I hear a vacuum leak coming from the rear valve cover where the breather tube attaches. What is curious to me is that when I disconnect that hose from the valve cover there is no change. Also where the hose attaches to the intake rubber tube through a tee fitting, when I pull that off there is no vacuum coming from that hole. Not sure if it should but wanted to mention that.
My gut tells me it is running on 5 cylinders and only at higher rpm will the 6th kind of kick in. On a test drive it does not accelerate well at all, but you can rev it up nicely.

I used some WD40 to check other places for leaks, but cannot find any. I am not sure if the sound I am hearing is really a leak or just the sound these engines make when breathing.

The local Mazda dealer is 25 minutes away and I am not positive this would make it like this.
I did clean the MAF and it looks like it had been replaced recently as well.

Exhaust comes out fine i believe, does not seem to be clogged.

Any ideas?

Thanks in advance,
Phil

 

So I pulled the intake to check all the gaskets and replaced the PCV hose. I also changed the boots on the coils so they are all new boots and one new coil.
Still runs rough.
I decided I might as well change the oil since it had been over a year since it had been driven. I saw the O2 sensor up front and decided to remove it. When I put my finger in the hole there was a big chunk of something in there. Too big to get out. I tried with a vacuum.
My guess is that the cats are fried so I am looking into that process right now.