I am hoping you guys can help me diagnose a problem with my grandparents' '93 Ranger 3.0 AT with 73K miles on the clock. For quite a few years, the truck has often started bucking (surging) after being driven for a long time (100+ miles). During this time, the "Check Engine" light turns on. It is difficult to even keep it at 55 mph, and it often downshifts to stay there - it's as if I'm climbing a steep hill, yet I'm on level ground. If I get on it real hard, it'll clear up and accelerate fine, but as soon as I start cruising, it comes back. This problem comes and goes at random - sometimes it will go away if the truck is turned off and back on, while other times it takes a full night of cooling off for it to go away. I have ran the codes before, and it showed the left bank was running lean.

This really wasn't a problem until I took the truck to Idaho this last week - it acted up REAL bad once on the way there, and on the way home, I had to fight it ALL the way back - 430 miles!

I ran the codes when I got home. There were no KOEO or KOER codes, but I came up with a TON of Continuous codes:

• 171 - No HEGO switching detected/adaptive fuel at limit (RH)
• 172 - HEGO snesor indicates system lean (RH)
• 173 - HEGO sensor indicates system rich (RH)
• 175 - No HEGO switching detected/adaptive fuel at limit (LH)
• 176 - HEGO sensor indicates system lean (LH)
• 177 - HEGO sensor indicates system rich (LH)
• 188 - Adaptive fuel lean limit is reached (LH)

It would seem both 02 sensors have bit the dust, but it seems odd both of them have died. What do you guys think? Would faulty O2 sensors create this bad of driveability issue, or is there something else I should be looking for?

I was thinking it could be clogged cat(s), but this would likely be a constant problem instead of intermittent. I was also wondering if a bad MAF or TPS could cause this, even if they aren't showing up as being bad during the test. Is there another sensor that could cause this?

Any help would be GREATLY appreciated, as I would like to get this problem fixed by tomorrow, since the truck is going to Colorado Tuesday.

If I do need new O2 sensors, anyone have recommendations on what brand I should buy or where I should go (we have Autozone, Napa, Schucks, and a few other local parts stores)?

Thanks A LOT!!!

 

Welcome to FTE!!

Have you changed the fuel filter and tested the pressure when the problem happens?

 

The fuel filter was replaced a couple months ago, but I have yet to check the fuel pressure when it does this. It's kind of hard to check it, since the truck only acts up after driving for quite a distance, and when it does, I'm nowhere near any of my tools.

I checked out the MAF, IAC Valve, and Air Temp Sensor with a multimeter, and they all checked out okay. I tried checking the oxygen sensors, but it's REALLY difficult to gain access to the wiring harness and connectors, especially on the right side. Any suggestions?

The truck is running fine right now, so I cleared all the codes, and am going to send it off to Colorado tomorrow. I'll check for codes when it gets back and do a little more diagnosis on it then.

Thanks for the suggestions so far, and any other ideas are more than welcome! I'd like to get this fixed some day...