97 Lesabre with surging problem

[swipter]

You know my 98 idles good and sometimes stumbles and shuts off. You can be going down the road and it will stumble and shut off. You can be turning a corner, slow, and it will do the same thing. It hasn't done it in a while but goes through cycles. I wonder if my EGR valve may be causing that? Sounds very similar to what was happening on this post. Very intermittent.

[lglm]

bad plug wire fixed my problem exactly like that, the original posting, my car didn't die just stumbled under load after being warmed up..

[Charliedavid]

Just one question, has anyone changed the catalatic converter and or the muffler? I have a 97 LeSabre custom with the same "surging" when the lockout converter engages, not everytime but most. It does it in 3rd and drive when the lockout kicks in, and my father, the previous owner, has replaced fuel pump(the whole sending unit actually), filter, and several smaller parts. Now the whole time the car has been in the family it has "thumped" for lack of a better term, when it's warming up and after it's shut off. We've traced it to the exhaust system, and there isn't nearly as much air flow from the tailpipe as the should be, and I can cover it completely with one hand with no issues. I know a clogged exhaust system can make a car run sluggish, but could the back pressure also be causing the surging issue? It stands to reason that less exhaust flow would cause less power, therefore it wouldn't shift properly at higher speeds/lower rpm's, correct? In my head it makes sense but I could use a more expert opinion. Thanks much!

[Blue Bowtie]

Exhaust restriction is indeed a problem. If it is excessive it can cause multiple symptoms. There are several ways to check the level of restriction, including temporary installation of a test pipe or pipes, removal of the oxygen sensor to allow temporary connection of a test pressure gauge, and infrared monitoring of exhaust components.