termitecontrol Posted January 27, 2015 Share Posted January 27, 2015 My comanche is idling weird, and I'm fairly certain it's caused by this strange hole in the headers. Does anyone here know what it's supposed to go to? If it was something a PO did to it trying to improve it or if there is something that is supposed to be plugged into it? Anyways, here's the pics. I know this one doesn't show it, but it might help show the location. Link to comment Share on other sites More sharing options...
Dillithium Posted January 27, 2015 Share Posted January 27, 2015 Could it be related to the EGR system? (Assuming the 2.8 had an EGR system) Link to comment Share on other sites More sharing options...
Eagle Posted January 27, 2015 Share Posted January 27, 2015 Bung for the O2 sensor. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 27, 2015 Share Posted January 27, 2015 Did the carb'ed 2.8 even have an O2 sensor? If so what would it be for? Unless those are the manifolds off a later FI 2.8... I'd also suspect it has something to do with EGR, but I have very little knowledge of the 2.8. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted January 27, 2015 Share Posted January 27, 2015 My 86 s-10 blazer has an o2 sensor . You never know what's been changed over the years Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 27, 2015 Share Posted January 27, 2015 I had an 84 2.8 S10, also with an O2 sensor. It should be an 18mm thread - try threading an 18mm spark plug into it to plug the hole. You might have to run an 18mm thread chaser first to clean up the threads. Any chain auto parts store carries these. Link to comment Share on other sites More sharing options...
gogmorgo Posted January 27, 2015 Share Posted January 27, 2015 Huh. You learn something new every day. Digging into it a bit more I've found out that computer controlled carbs actually had an O2 sensor, and actually used it alongside a TPS to, you know, adjust things in the carburetor. Looks like it's mostly a Cali emissions thing, although some 49-state vehicles did escape from their factories with it. That's actually pretty cool, (no really, it's an automated carburetor!) although needlessly complex and probably much less effective (and reliable) when compared to fuel injection. Link to comment Share on other sites More sharing options...
Eagle Posted January 27, 2015 Share Posted January 27, 2015 Yep, computer-controlled carburetor. Piece of excrement, but computer controlled excrement. I think you may need an O2 sensor in there -- I don't think it was only in California. Link to comment Share on other sites More sharing options...
Rockfrog Posted January 27, 2015 Share Posted January 27, 2015 Later CJ's and early YJ's also ran a computer controlled carb ... It still required jetting and initial adjustments to get going. Not as auto adjusting as one would think. They were pretty common on most passenger cars early to mid 80's as well. Never did have one that worked well or as intended ... Probably why they had a short life span between basic carbs and the TB systems that replaced them just before MPFI/SEFI became the norm on most vehicles in the 90's. In most cases many computer controlled carbs were "dumbed" down so they ran right again. Link to comment Share on other sites More sharing options...
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