'91 Buick cat check?

[huey286]

Anybody know how I can check the cat converter myself? Same car, '91 Buick Les, 180K miles. If I take it to shop, I'm sure they will say it's bad, as I once had them tell me my battery was bad, when it was power seat switch draining it (they sold batteries, Wal-Mart) There is no rotten egg smell, or anything. wondering if it could be coming apart inside and occasionally blocking exhaust. no SES light, have code 29- quad driver module circuit. What does that pertain to? Thanks, Gene

[avatar307]

Do you mean 26? 29 is 4th Gear Switch.

[avatar307]

From http://www.troublecodes.net/articles/

From the articles dealing with troubleshooting and reseting the ECM, this link talks specifically about Quad Driver Modules (QDM). Which... apparently... are part of the ECM that may require you to replace the ECM.

http://www.troublecodes.net/articles/quaddriver.shtml

Google is a wonderful thing.

[huey286]

Originally Posted by huey286

Anybody know how I can check the cat converter myself? Same car, '91 Buick Les, 180K miles. If I take it to shop, I'm sure they will say it's bad, as I once had them tell me my battery was bad, when it was power seat switch draining it (they sold batteries, Wal-Mart) There is no rotten egg smell, or anything. wondering if it could be coming apart inside and occasionally blocking exhaust. no SES light, have code 29- quad driver module circuit. What does that pertain to? Thanks, Gene

Thanks for the reply, Yes it's 29. The Haynes manual says 26,27,28,29 all pertain to the same. I will check the Google link you mentioned. Thank You! Do you know for sure if EEC cannister is to hold any vacuum, or just lets filtered outside air come in, and pull along any fuel fumes that might have come from tank? Gene

[avatar307]

There is a solinoid that controls a diaphram inside. One of the connections should hold a minimum pressure when the solinoid is engaged, and another connection should hold pressure when it is not engaged.

Pretty sure anyway, I don't feel like re-reading that section, but you check it using a vacuum pump, so the connections do hold vacuum. Minimum vacuum pressure of 20Hg I think.

I believe the theory of operation is to pull fuel vapors into the canister and inject them into the intake manifold to be burned. Or to filter out the free hydrocarbons through the charcoal filter before reaching the purge valve. Either way, the idea is to not release free hydrocarbons into the air.