Codes 311 and 173 fixed.
#1
06-04-2014, 06:39 PM
Join Date: Jul 2013
Location: Eugene, OR
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Codes 311 and 173 fixed.
I ran a scan on my '92 F150, 5.8 L using the INNOVA 3145 code reader. It gave a 111 pass on the KOEO part, a 173 (HEGO reads rich) on the Continuous Monitor part, and code 311 (Thermactor system inoperative) 0n the KOER part.. I know many have solved these codes but I thought some additional experience might help someone.
First, the thermactor system was a bit of a mystery to me. I read up on it in the Haynes manual and on line. It's a nutty system which is no longer used. The fix turned out to be fairly easy. I did a visual check on the many vacuum lines used and all looked good. But, when I ran my fingers along the plastic vacuum tubes, I felt a small bump at the elbow connection to the diverter valve. I disconnected that line and found it had melted right where the tube enters the rubber elbow thus cutting off the vacuum from the diverter valve. I cut off the melted part ( about an inch) and reconnected the elbow. I also got some heat protective cover for the tubing since it ran a few inches from the exhaust manifold.
This cured the 311 code.
Fortunately, I didn't have to dig into the rest of the thermactor system which the Ford engineers carefully hid behind the engine in the most hard to reach place they could have found.
The oxygen sensor code was fun.
I checked for the warm up voltage at the plug to the sensor which was 12v with key on. There was no leakage resistance between the sensor signal connection and ground.
Next I used the Break Out Box I got off of Ebay. It's a pain to get connected but a real pleasure to use for trouble shooting. An analog voltmeter connected from the oxygen sensor to ground showed the problem. The old sensor took a very long time to start pulsing and then its switching was slow and erratic. Before it started switching, it gave about .9 volts which the computer saw as a rich condition thus the 173 code.
A new oxygen sensor worked fine and the 173 code is now gone.
This may be simple stuff but I wanted to share a good day wrenching.
First, the thermactor system was a bit of a mystery to me. I read up on it in the Haynes manual and on line. It's a nutty system which is no longer used. The fix turned out to be fairly easy. I did a visual check on the many vacuum lines used and all looked good. But, when I ran my fingers along the plastic vacuum tubes, I felt a small bump at the elbow connection to the diverter valve. I disconnected that line and found it had melted right where the tube enters the rubber elbow thus cutting off the vacuum from the diverter valve. I cut off the melted part ( about an inch) and reconnected the elbow. I also got some heat protective cover for the tubing since it ran a few inches from the exhaust manifold.
This cured the 311 code.Fortunately, I didn't have to dig into the rest of the thermactor system which the Ford engineers carefully hid behind the engine in the most hard to reach place they could have found.
The oxygen sensor code was fun.
I checked for the warm up voltage at the plug to the sensor which was 12v with key on. There was no leakage resistance between the sensor signal connection and ground.Next I used the Break Out Box I got off of Ebay. It's a pain to get connected but a real pleasure to use for trouble shooting. An analog voltmeter connected from the oxygen sensor to ground showed the problem. The old sensor took a very long time to start pulsing and then its switching was slow and erratic. Before it started switching, it gave about .9 volts which the computer saw as a rich condition thus the 173 code.
A new oxygen sensor worked fine and the 173 code is now gone.
This may be simple stuff but I wanted to share a good day wrenching.
Thread
Thread Starter
Forum
Replies
Last Post
scott9320
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
1
08-29-2003 08:00 PM
rocky50
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
2
06-20-2000 03:41 PM
