1999 ZX2 intermittent power loss P1131

[Mazda_Powered]

Well now that I'm done with one headache (the 626) I'm left to deal with this one haha.

1999 Escort ZX2 with 65,000mi, automatic. Purchased at 60,000mi

Got code p1131 from her, which indicates a lean condition at the front o2 sensor. So I changed out the nasty old fuel filter and installed some new plugs (all parts on the car are original LOL).

Code came back after about 300 miles, this time with more pronounced issues, such as intermittent power loss, where as before it was just the CEL that was indicating any issue.

plugged in the scan tool, front o2 sensor is working great, nice VVVV action going on LOL (0-1v sweep)

rear o2 sensor seems a bit lazy until throttle is applied, _____VV_____ is what the scanner was showing at idle. Was sitting at .005V

NOW. I've been reading, and apparently there's over 20 causes that can trigger the p1131 code, and it's typically NOT the sensors fault.

I'm going to get some contact cleaner for the MAF sensor, then if that doesn't work, figure out a way to smoke the intake and vac system.

Any other suggestions?

[nerd racing]

Sell it and get another Mazda?

[racerrex01]

Hey i work on those things alot at the shop im at look at the pcv tube real good for leaks,take the oil cap off while the engine is running and see if the rpms change had a bunch of those with stuck pcv valves.

[Mazda_Powered]

Well no vac leaks were found via starter fluid. also cleaned the MAF wire with contact cleaner...soo we'll see what happens there. Looked clean to me though.

Sell it and get another Mazda?

haha it's my girlfriends car technically, so I can't do that unless it's a car she can drive as well. I wouldn't mind a P5 since they have the manual shifting option with the ATX transmission.

Hey i work on those things alot at the shop im at look at the pcv tube real good for leaks,take the oil cap off while the engine is running and see if the rpms change had a bunch of those with stuck pcv valves.

Awesome, thanks for the heads up. I will check the PCV valve out.

edit: wtf PCV valve, there's 2 of them on the car?

[KAinjection]

I know you said you checked vacuum leakes but the small vacuum line running to the fuel pressure regulator to the intake seems to rub on something and make a small hole in it causing a vacuum leak. I didnt know it was there and actually discovered it by accident since the car ran fine, but never drove it long enough to find if it would set a code. The broken engine and the used engine that replaced it both had the same issue.

Also keep an eye on the plastic thermostat housing in your pic above, the plastic seems to get brittle and leak after some age.

[Mazda_Powered]

I'll check that out tomorrow, thanks man!

As for the thermostat housing, it seems to be really solid actually, I did the t-stat on her a while back without any issues. I definitely hear you with heat and stiff plastics though lol.

Picked up 1/2 of the PCV valves today as the store I went to only had one ...so I'll replace the one at the block (in the pic) if both turn out to be "ok".

[Mazda_Powered]

ok so today I found a post cat exhaust leak before the post cat o2 sensor, it was a pin hole so I cleaned it up and sealed it with 1500* cement, and also changed out the original PCV valve haha, it shows it too. Car idles much smoother, just waiting for a reason to go for a drive now.

edit: also my zx2 has only 1 pcv valve by the exhaust manifold, the one at the valve cover is simply a 1/2" nipple off the valve cover to a canister that brings vac from the air box....hmm wonder if the air box would have a pcv valve on it as it's a big one...hmm lol

[Mazda_Powered]

Impressions:

dislike how sensitive the car is to pin hole exhaust leaks, but thrilled to say that was causing my intermittent power loss, and time will tell to see if p1131 comes back or not.