OK grey streak 92-seems i have no vacuum leaks and am showing a code 311 --any other ideas --Thanks TR

 

Ok, you asked for it...

Code 311 - Thermactor system inoperative (bank 1 dual HEGO).

Checks should be vacuum lines and routing to and from the diverter valve (behind the passenger cylinder head), to and from the TAB (Thermactor Air Bypass) and TAD (Thermactor Air Diverter) solenoids. No leaks is fine but is there actually vacuum present in that part of the system?

If all vacuum lines, routing and at least 9-10" of vacuum is present the next check is airflow from the air injection pump (smog pump) up to and through the diverter valve.

If these check out, a check of the electrical connections to the TAB/TAD solenoids is in order. Assuming the connections are good, run the KOEO test. AFTER the last memory Code put the throttle to the floor and release it. With a voltmeter/multimeter (set to read DC nearest but not less than 12VDC) probe each terminal of the TAB and TAD solenoids with the red lead while the black lead is secured to a good negative (ground) source. If both solenoids are functioning properly at this point EACH ONE should have one (1) terminal with +12VDC and one (1) with 0VDC. If this is NOT the case, you have a wiring problem between pin 51 (TAB) or pin 11 (TAD) of the ECM and the affected solenoid. If the solenoids pass this first part of the test put the throttle to the floor and release it again. Now, ALL terminals on BOTH solenoids should show +12VDC on your meter. If there is a terminal without battery voltage at this point, replace the solenoid so afflicted.

Code 311 is a generic trouble code typically associated with plumbing problems in the Thermactor and/or vacuum system. However, the detailed solenoid troubleshoot can be necessary if one has failed since this is the only test short of disconnecting the solenoids individually and feeding battery voltage to them. This practice however will NOT reveal issues within the wiring harness or vehicle connections.

 

Welcome back Grey!

 

Thanks to all. I think I needed some time away. I haven't been posting as much but I can't NOT put information out here if I've got it to give. And I will say that as unbiased as I'd LIKE to be, I have my opinions and they rear their ugly heads sometimes. I sincerely appreciate the support but most importantly I take a certain satisfaction in trying to put good information out here.

TR,
If you need more details on troubleshooting the Thermactor, let me know. There are one or two extremely remote possibilities that I didn't include in my initial post simply because they are so unlikely.

 

I dunno if this will help, you're sorta far away from being at this point.. but i've been chasing that same code in my 90' (well, the 2 digit equivilent) forever. I found out it was a low-vacuum situation caused by a stretched timing chain. That one, then occasionally EGR would throw codes, but that's it.

 

Since i have the time and effort to park my 92 for a while ,i am taking one step and self educating as i go along.No Hurry, Glad your back. I shall take all info available and try the troubleshooting.In the process of replacing all vacuum lines (needed it anyway). Thanks TR WILL UP DATE SOON

 

Ok looking back through receipts , saw where my air pump was replaced in 08 and had a warranty, swapped it out and code 311 has disappeared.I have replaced all the plastic lines with hose,checkd all the emission sensors-valves switches etc.Since throwing codes and having the stumble on acceleration, i have purchased a obd1-2 code reader, vacuum pressure guage .The only code i get on koer is a 538 , koeo is 111, thanks Grey AND FTE TR

 

Grey are you back?

 

It would appear so. Unless my evil twin has been posting on my behalf. I needed a break. So I took a few months, bought a new toy (1968 DeVille convertible... yeah Cadillac/GM, so shoot me), gave it to my wife, and now I'm elbow-deep in an engine/transmission swap in the Bronco that should have been finished two years ago.

 

Differances of opion aside lol it is good to have you back on here man. Never know when I may have to work on one of these "new style" trucks and will need your great advice.

 

Differing opinions are what make this site work. Letting the differences get to you kills the experience.

 

Very true. I have learned that as well. But it is still good to see you back.

 

Greystreak, thank you for coming back. your advice is so solid that I was hoping you would be back. Had a question in regards to the 311 code. You gave me some advice before on my IAC issue. The Bronco is running better then ever but I got that darn check engine light. My light comes on after driving a mile or so. At idle it will not come on. I looked at the vacume lines and the tan one going to the diverter valve was disconnected. I reconnected it thinking I found the culprit but was wrong. My question is Will a bad air pump throw the 311 code but let the engine run at idle with no CEL? The CEL only comes on when I drive. Thanks for the help and welcome back.

 

Code 311 - Thermactor System inoperative (bank 1 dual HEGO).

Translation - Thermactor system (which includes the smog pump, diverter valve, TAB and TAD solenoids and all interconnecting wiring and vacuum lines) was not providing air through the system during the test.

Troubleshooting - Check/repair any and all loose electrical connections to the TAB and TAD solenoids. Check/repair any loose, cracked, disconnected vacuum lines within the system (never hurts to check 'em all if you are going this far).

There is a more specific troubleshooting procedure but since you mentioned the disconnected vacuum line and made no mention of having cleared the ECM memory of stored Codes, I would follow the tips above, clear the ECM memory and retest. If Code 311 returns, let us know. There is a specific procedure for troubleshooting through the entire Thermactor system. This is a more detailed explanation of what I posted here. I know I've posted the tedious part of the procedure as well but I can't find it now.

 

Since the CEL only comes on when you drive there may be another code in CM, Continuous Memory.