Desperate Need help understanding readout.

[88cougar]

Please bear with me. This may be long winded.

I am trying to solve a driveability issue on a 99 Explorer Limited AWD. Mileage is 120,000 and the only mod is a MAC intake. I suspect the MAF is shot but I wanted confirmation before I shell out $200.00 for a reman. one. I have tried cleaning it with no success (have cleaned it successfully in the past). The truck runs fine until it goes into closed loop at which point power drops off idle is rough and detonation occurs. I borrowed a scan tool to check for codes but there are none. I did a live data stream and here are the results:

Reading was done with Mac Tools ET-97 after a 15 minute drive and while idling in park.

RPM 725
Engine Temp 189 F
IAT 102 F
Timing 18 deg
MAF 0.63 lb/m
TPos 18%
Load 34.5%
STFT B1 -1.57 to 3.11
LTFT B1 4.67%
STFT B2 -1.57 to 3.11
LTFT B2 7.02%
O2 B1 S1 0.08 to 0.7 V
O2 B1 S2 0.08 to 0.2 V
O2 B1 STF -2.0% to 2.0%
O2 B2 S1 0.08 to 0.77 V
O2 B2 S2 0.08 to 0.77 V
O2 B2 STF -2.0% to 2.0%

I also had a notice EVAP SYST NOT COMPLETE.

I'm new to all of this and have no idea what I am looking at. Could someone please explain what these numbers mean? Also is 34% load and 18% throttle at idle high or is that normal.

Thank-you for your patience and replies.

 

[96eb96]

This is from the manual:
GENERIC OBD II PID VALUES PID Hot Idle 2500 RPM Units
LONGFT1 (-)20-(+)20 (-)20-(+)20 %
LONGFT2 (-)20-(+)20 (-)20-(+)20 %
LOAD 27-35 20-25 %
MAF 4.8-7 18.1-21 G/S (you are in spec with your units)
SHRTFT1 (-)10-(+)10 (-)10-(+)10 %
SHRTFT2 (-)10-(+)10 (-)10-(+)10 %
SHRTFT11 (-)10-(+)10 (-)10-(+)10 %
SHRTFT12 95-100 95-100 %
SHRTFT21 (-)10-(+)10 (-)10-(+)10 %



I don't see anything that is crazy, I looked at the reference values in the manual. The STFT /LTFT are your fuel trims, where fuel is added or subtracted. If the MAF was bad the computer would assume a lean condition and those would be over 12 or even much higher. Also the MAF at idle is normal. If your scanner can graph see if the maf shoots up quickly when you hit the pedal in park. It should also drop off quickly.

 

[budwich]

The "switching levels" of your O2 sensor on one side perhaps might be a little "low", perhaps indicating an issue on that side of the engine, not necessarily a sensor problem. If I understand it "right", it appears to be somewhat on the lean side.

 

[88cougar]

Thanks for your replies. I did graph the MAF. It would shoot up quickly but the drop off wasn't as sharp. I now have no idea what is causing the problem. The best way to describe it is it feels like the engine is overheating. At crusing speed it seems fine but under load I get serious detonation and the truck shakes at idle. I am going to pull the plugs to see what is going on and try to find a used MAF to see if that makes any changes. Once again Thanks!

 

[88cougar]

O.K. I replaced the MAF with a reman one. There is a slight improvement in the idle but the problem still persists. After researching the problem on this site I am leaning towards the camshaft position sensor. My question is: Do I just replace the sensor or do I need to replace the synchro as well? Help me please I'm stumped.